JP2006221887A - High-frequency plasma generator, surface treatment apparatus comprising the same, and surface treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treatment apparatus and a surface treatment method for performing large-area and uniform plasma surface treatment by suppressing the influence of standing waves peculiar to VHF or UHF plasma in the application of the VHF or UHF plasma to the surface treatment of a substrate such as CVD and etching. <P>SOLUTION: A VHF plasma generator can generate large-area/uniform plasma having a means for generating a plurality of standing waves having different positions of antinodes of electromagnetic waves between electrodes and superposing them. The VHF plasma surface treatment apparatus and the surface treatment method comprise the VHF plasma generator. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface treatment apparatus and a surface treatment method for performing a predetermined treatment on a surface of a substrate using plasma. In particular, the present invention is based on ultra-high frequency plasma having a low electron temperature and capable of generating high-density plasma, that is, high-frequency power in the VHF band (30 MHz to 300 MHz) and UHF band (300 MHz to 3 GHz). The present invention relates to a surface treatment apparatus and a surface treatment method using generated plasma.

  Various kinds of processing are performed on the surface of the substrate using plasma to manufacture various electronic devices. LSI (Large Scale Integrated Circuit), LCD (Liquid Crystal Display) TFT (Thin Film Transistor), amorphous Si solar cell, thin film Already put into practical use in the fields of polycrystalline Si solar cells, photoconductors for copying machines, and various information recording devices. In addition, practical application is also progressing in the field of manufacturing ultra-hard films such as diamond thin films and cubic boron nitride (C-BN).

The above technical fields include amorphous Si-based materials, microcrystalline Si-based materials, polycrystalline Si-based materials, crystalline Si-based materials, thin film formation, etching, oxides, metals, organometallic compounds, organosilicon compounds, and organic compounds, There are a variety of methods such as surface modification and coating, but all utilize the chemical and physical action of reactive plasma. The apparatus and method relating to the generation of the reactive plasma are roughly classified into three typical techniques.
The first representative technique is described in, for example, Patent Documents 1 to 3, and is characterized in that two parallel plate electrodes, which are a non-ground electrode and a ground electrode, are used as a pair for plasma generation. The second representative technique is described in, for example, Patent Documents 4 and 5, and is characterized by using a pair of rod electrodes or ladder-type electrodes and plate electrodes for plasma generation. The third representative technique is described in Patent Document 6, for example, and is characterized by an antenna system.

  For example, Patent Documents 2 and 3 describe techniques using a balance-unbalance converter as a technique for preventing power loss and suppressing generation of unnecessary plasma other than between electrodes.

The features of the technique described in the above document are roughly as follows. In the technique described in Patent Document 1, a non-grounded electrode is a square electrode, a plurality of first power supply points are arranged on the side surface of the first side of the rectangular electrode, and a second electrode facing the first side is provided. A plurality of second power supply points are arranged on the side surface of the side, and the voltage of power supplied to the plurality of first power supply points and the power supplied to the plurality of second power supply points By varying the voltage phase difference with respect to time, the electric field distribution between the pair of electrodes is averaged, and as a result, the spatial distribution of the plasma intensity is made uniform. In this technique, a standing wave can be generated by interfering with traveling waves of two electric power supplied so as to propagate in directions opposite to each other, and the position of the antinode of the standing wave can be changed with time. Is possible.
In the technique described in Patent Document 2, the pair of electrodes has a square shape, and the first and second sides of the electrodes positioned in directions orthogonal to each other are respectively provided in the output circuit of the power supply system. A plurality of connected power supply points are installed, and a reactance adjustment device corresponding to each of the plurality of power supply points is installed on the opposite side of the plurality of power supply points. . In this technology, by controlling the reactance adjustment device corresponding to the plurality of power supply points, by controlling the phase of the reflected wave, the traveling wave of the supplied power and the reflected wave are caused to interfere to generate a standing wave. And the position of the antinode of the standing wave can be moved.
In the technique described in Patent Document 3, a plurality of openings are installed in a pair of electrodes, power supply points are arranged at the edges of the openings, and the power supply system is connected to the balance-unbalance conversion device and the balanced transmission path. Power supply. In this technology, the power supplied from the adjacent apertures is superimposed on the standing wave generated by the relationship between the traveling wave and the reflected wave, and the spatial distribution of the plasma intensity between the electrodes is made uniform. It is possible to
The technique described in Patent Document 4 is characterized in that a phase adjustment circuit that adjusts the phase of reflected power is connected to the tip of the pair of electrodes on the opposite side of the power supply point. In this technique, by controlling the phase adjustment circuit, the phase of the reflected wave can be adjusted, the traveling wave of the supplied power can interfere with the reflected wave, and a standing wave can be generated, and The position of the antinode of the standing wave can be moved.
The technique described in Patent Document 5 changes temporally the phase difference between the voltage of power supplied to one power supply point on the electrode and the voltage of power supplied to at least one other power supply point. Thus, the electric field distribution between the pair of electrodes is averaged, and as a result, the spatial distribution of the plasma intensity is made uniform. In this technique, it is possible to generate a standing wave by interfering with traveling waves of two electric power supplied from opposite directions, and to change the position of the antinode of the standing wave with time. .
The technique described in Patent Document 6 is characterized in that the electrode is formed by folding a linear conductor so as to be included in a plane with reference to the central point, and the central point is used as a feeding point. The shape of this electrode is, for example, U-shaped or M-shaped. Further, the U-shaped or M-shaped electrode serves as an antenna to radiate supplied power to the space.

  The technique described in Non-Patent Document 1 is that an H-shaped feeding band is installed on the back side of the surface of the non-grounded electrode in contact with plasma, and a plurality of feeding points are installed on the H-shaped feeding band. It is a feature. The technique described in Non-Patent Document 2 is that a coil is installed on the opposite side of the feeding point of the non-grounded electrode, that is, on the end of the electrode located in the power propagation direction, and a feeding line connecting the power source and the pair of electrodes, It is characterized in that the position of the antinode of the standing wave generated in the electrode is shifted.

Japanese Patent Application Laid-Open No. 2002-12977 (second page, FIG. 1, FIG. 10-11) Japanese Patent No. 3575014 (page 1-3, FIG. 6-10) JP-A-2004-235673 (page 2-3, FIG. 9-11) JP-A-11-243062 (first page, FIG. 1, FIG. 7) Japanese Patent No. 3316490 (first page, FIG. 1, FIG. 8) JP 2000-345351 (Page 2, FIG. 1, FIG. 5, FIG. 7)

J. Kuske, U. Stephan, O. Steinke and S. Rohleck: Power feeding in large area PECVD of amorphous silicon, Mat. Res. Soc. Symp. Proc. Vol. 377 (1995), p.27-32. L. Sansonnens, A. Pletzer, D. Magni, AA Howling, Ch. Hollenstein and JPMSchmitt, A voltage uniformity study in large-area reactors for RF plasma deposition, Plasma Source Sci. Technol. 6 (1997), p. 170-178.

  The above-mentioned plasma surface treatment technology, that is, the plasma surface treatment apparatus and the plasma surface treatment method, reduce the product cost and increase the area of the product due to the improvement in productivity in any of the industrial fields such as LCD, LSI, electronic copying machine and solar cell. The need for large area, uniformization, and high-speed processing is increasing year by year for improving performance (specifications) such as wall-mounted TV. In particular, in the field of thin-film silicon solar cells, which are expected to accelerate the spread of practical use as a new energy source that responds to energy resource problems and global environmental problems, further reduction in production costs is required as a social need. ing.

  In order to meet the above needs, recently, as a technical trend, not only in industry but also in academic societies, both plasma CVD (chemical vapor deposition) technology and plasma etching technology are capable of high performance and high speed processing (low) Research on practical application of plasma CVD technology using a power supply in the VHF band (30 MHz to 300 MHz) and UHF band (300 MHz to 3 GHz), which is characterized by high density plasma generation at an electron temperature, has become active. However, in the prior art, there are still problems as described below, and there is a problem in the field of the above needs.

  The first problem is a VHF and UHF plasma surface treatment apparatus and VHF for high productivity processes capable of increasing the speed, large area, and uniformity (productivity improvement and performance improvement) of surface treatment using VHF and UHF plasma. And a breakthrough of the technology related to the UHF plasma surface treatment method. Generally, in the LCD field, the film thickness distribution ensures reproducibility of about ± 5%, and in the solar cell field, the film thickness distribution ensures reproducibility of about ± 10%. It has become. However, the technology for increasing the speed, area, and uniformity of VHF plasma, which appeared as the world's first attempt in 1987, has not made much progress. In the conventional VHF plasma technology, for example, in the case of manufacturing an a-Si film, assuming that reproducibility is ensured, when the substrate area is about 50 cm × 50 cm, the film thickness distribution is about ± 10 to 15%, and about 100 cm × 100 cm. The film thickness distribution is about ± 20 to 40%, and there is a problem that the above index cannot be cleared.

The direct cause of the non-uniformity of the film thickness distribution is the non-uniformity of the plasma density. The non-uniformity of the plasma density is caused by the wave interference phenomenon that is a problem inherent to the VHF and UHF. There is a generation of standing waves. Since this standing wave problem is a fundamental phenomenon associated with the propagation of electromagnetic waves, there has been no drastic solution in the past, and the idea described in Patent Documents 1 to 6 is being put into practical use as the next best measure. . However, both technologies have the following problems. That is, the problem of standing waves cannot be fundamentally solved.
(1) The technique described in Patent Document 1 changes the phase difference between the voltages of power supplied from two opposite sides of a rectangular electrode temporally, for example, at a frequency of several kilohertz, in a sawtooth shape, The position of the antinode of the generated standing wave is moved between the pair of electrodes, and the time average is made uniform. Regarding the film thickness distribution, in the case of amorphous Si film formation, a film thickness distribution of about ± 10 to 15% is obtained when the substrate area is about 50 cm × 50 cm, but it is considered to be ± 20% or more for about 100 cm × 100 cm. .
(2) Since the technology described in Patent Document 2 controls the phase of the reflected wave of power by installing reactance adjustment devices corresponding to the plurality of power supply points on the opposite side of the plurality of power supply points, respectively. In the condition where the power absorption rate is high, for example, plasma generation at a pressure of several hundreds of Pa to several thousand Pa, the intensity of the reflected wave becomes weak, and the reflected wave cannot be controlled. That is, there is a drawback that it can be applied only when the plasma generation pressure is several hundred Pa or less.
(3) In the technique described in Patent Document 3, the strength of the plasma between the electrodes is obtained by superimposing standing waves generated by the power supplied from the openings adjacent to each other in the relationship between the traveling wave and the reflected wave. Therefore, it is necessary to select a distance corresponding to the power supply frequency, that is, the wavelength to be used. That is, it is an essential condition that the power supply frequency is selected in advance, and the wavelength of the propagation power is shortened according to the strength of the plasma density, so that the uniformity of the plasma depends on the strength of the plasma density. is there.
(4) The technique described in Patent Document 4 is similar to the technique described in Patent Document 2, in which a phase adjustment device is installed on the opposite side of the power supply point to control the phase of the reflected wave of power, so that power absorption In a high rate condition, for example, plasma generation at a pressure of several hundreds of Pa to several thousand Pa, the intensity of the reflected wave becomes weak and the reflected wave cannot be controlled. That is, there is a drawback that it can be applied only when the pressure of plasma generation is about several hundred Pa or less.
(5) The technique described in Patent Document 5 is similar to the technique described in Patent Document 1, in which the voltage of power supplied to one certain feeding point on the electrode and the power supplied to at least one other feeding point are described. VHF plasma surface treatment apparatus for processing, since the electric field distribution between a pair of electrodes is averaged by changing the phase difference of the voltage of the time, resulting in uniform spatial distribution of the plasma intensity The VHF plasma surface treatment method has a drawback that the plasma fluctuates at a frequency of, for example, several kHz, and is not suitable for high quality film production or high quality etching processing. As for the film thickness distribution, in the case of amorphous Si film formation, a film thickness distribution of about ± 10 to 15% is obtained for a substrate area of about 50 cm × 50 cm, but about 100 cm × 100 cm is considered to be ± 20 or more. Yes.
(6) Since the technique described in Patent Document 6 is an antenna system, that is, inductively coupled plasma generation, there is a restriction that the pressure condition is several Pa or less. That is, there is a disadvantage that it is impossible for an application in which the pressure condition such as microcrystalline Si is several hundred to several thousand Pa. In addition, it is presumed that it is difficult to grasp the appropriate conditions of the film forming conditions because it is easily influenced by the shape of the vacuum vessel around the electrode and the grounding conditions.

  Furthermore, as a second problem, there is a technical development of a VHF or UHF plasma generator having high applicability to a mass production apparatus. In general, the basic line of production equipment in a high-productivity process has three types: an inline type device, a multi-chamber type device, and a roll-to-roll type device. When a pair of electrodes in the plasma processing chamber is connected to the power supply cable, for example, when the shape of the pair of electrodes is rectangular, there is a need for means that can connect both using only one of the four surrounding sides. However, there is a problem that conventional VHF and UHF plasma technologies cannot meet this need. Note that the technology described in Patent Documents 1 to 6 described above is only the technology described in Patent Document 6 that can meet this need. However, this technique is considered to have a low practical value because the pressure condition is limited to several Pa or less as described above.

  As described above, in the prior art, it is still difficult to apply VHF plasma CVD and plasma etching to a large area substrate necessary for mass productivity improvement and cost reduction, for example, a large area substrate exceeding a size of 1 mx 1 m class. It is difficult. In other words, in order to respond to issues such as high-speed, large-area, and uniform plasma surface treatment, VHF and UHF plasma technologies are attracting attention as one technology trend, and development research on their practical application is being conducted. However, due to technical difficulties, surface treatment equipment capable of increasing the speed, area and uniformity of VHF and UHF plasma for large area substrates exceeding 1 mx 1 m class and successful examples of the method have been announced. Not.

  In other words, the specific technical problems that the VHF and UHF plasma fields currently have are, first, the creation of a large area and uniform technology that can suppress the standing wave generated between a pair of electrodes, and second, the substrate It is the creation of a power supply means that places little restrictions on the installation of the transport device.

  Therefore, the present invention fundamentally suppresses the influence of standing waves necessary for solving the above-described problems of the prior art, enables high-speed, large-area, and uniform plasma surface treatment, and A high-frequency plasma generator for realizing an idea capable of realizing a power supply means that places little restriction on the installation of a substrate transfer device, a high-frequency plasma generator for realizing the idea, a plasma surface treatment apparatus and a plasma constituted by the high-frequency plasma generator An object is to provide a surface treatment method.

  In order to solve the above problems, the present invention is characterized in that a high-frequency plasma generator, a plasma surface treatment apparatus and a plasma surface treatment method constituted by the high-frequency plasma generator are as follows.

That is, according to the first aspect of the present invention, the surface of the substrate disposed in the vacuum vessel is processed using plasma generated using the power of the output of the high-frequency power source whose oscillation frequency belongs to the VHF band or the UHF band. In the high-frequency plasma generator used for the surface treatment apparatus, a plurality of standing waves having different antinode positions of electromagnetic waves are generated between the electrodes, and means for superimposing them is provided. To do.
Further, the invention according to claim 2 of the present application is the high-frequency plasma generator according to claim 1, wherein means for generating a plurality of standing waves having different antinode positions of the standing waves of electromagnetic waves and superimposing them is provided. And a means for controlling the positions of the antinodes of the plurality of standing waves.
The invention according to claim 3 of the present application is the high-frequency plasma generator according to claim 2, wherein the first standing wave and the second standing wave having different antinode positions of the standing wave of the electromagnetic wave are generated. And means for superimposing the first and second standing waves.
The invention according to claim 4 of the present application is the high-frequency plasma generator according to any one of claims 2 and 3, wherein a plurality of standing waves are respectively provided in a plurality of directions in a plane parallel to the electrode. And a means for superimposing the plurality of standing waves.
The invention according to claim 5 of the present application is the high-frequency plasma generator according to claim 4, wherein the first standing wave is in one of two directions orthogonal to each other in a plane parallel to the electrode. And a second standing wave, a third standing wave and a fourth standing wave in the other direction, and the first, second, third and fourth standing waves It is characterized by having means for superimposing.
According to a sixth aspect of the present invention, in the high-frequency plasma generator according to the third aspect, the first standing wave and the second standing wave are generated, and the first and second standing waves are generated. The means for superposing the standing wave has a pair of electrodes composed of first and second electrodes having a plurality of feeding points, two output terminals, and a phase difference between voltages of the outputs of the two output terminals. A first high-frequency power source that can be arbitrarily set, first and second impedance matching units respectively connected to two output terminals of the first high-frequency power source, and the first high-frequency power source A second high-frequency power source that is independent and has two output terminals and that can arbitrarily set the phase difference of the output voltage of the two output terminals, and the two output terminals of the second high-frequency power source A third and a fourth impedance matcher connected to each of the And the output terminals of the first and third impedance matching devices are connected to the first feeding point arranged on the first electrode, and the propagation of electromagnetic waves to the first feeding point The output terminal of the 2nd and 4th impedance matching device is connected to the 2nd electric power feeding point arrange | positioned in the position which becomes the opposing point, It is characterized by the above-mentioned.
According to a seventh aspect of the present invention, in the high-frequency plasma generator according to the third aspect, the first standing wave and the second standing wave are generated, and the first and second standing waves are generated. The means for superposing the standing wave has a pair of electrodes composed of first and second electrodes having a plurality of feeding points, two output terminals, and a phase difference between voltages of the outputs of the two output terminals. A first high-frequency power source that can be arbitrarily set, first and second impedance matching units respectively connected to two output terminals of the first high-frequency power source, and the first high-frequency power source A second high-frequency power source that is independent and has two output terminals and that can arbitrarily set the phase difference of the output voltage of the two output terminals, and the two output terminals of the second high-frequency power source A third and a fourth impedance matcher connected to each of the And an output terminal of the first impedance matching device is connected to a first feeding point disposed on the first electrode, and an opposing point on the propagation of electromagnetic waves with respect to the first feeding point The output terminal of the second impedance matching device is connected to a second feeding point arranged at a position having a relationship, and is parallel to a line segment connecting the first feeding point and the second feeding point. The output terminals of the third and fourth impedance matching devices are respectively connected to the third and fourth feeding points arranged at positions that are in such a relationship. .
According to an eighth aspect of the present invention, in the high-frequency plasma generator according to the third aspect, the first standing wave and the second standing wave are generated, and the first and second standing waves are generated. The means for superposing the standing wave includes a pair of electrodes composed of first and second electrodes having a plurality of feeding points, arbitrary pulse modulation is possible, and two output terminals are provided. A first high-frequency power supply capable of arbitrarily setting the phase difference of the output voltage of the output terminal, and first and second impedance matchers connected to the two output terminals of the first high-frequency power supply, respectively. And any pulse modulation synchronized with the pulse modulation signal of the first high-frequency power supply, and two output terminals, and the phase difference between the output voltages of the two output terminals can be arbitrarily set A second high-frequency power source and two output terminals of the second high-frequency power source A third impedance matching device and a fourth impedance matching device connected to each other, and outputs of the first and third impedance matching devices to a first feeding point disposed on the first electrode. The second and fourth impedance matchers are connected to a second feed point that is connected to a terminal and is located at a position that is a point opposite to the first feed point in the propagation of electromagnetic waves. The output terminal is connected.
According to a ninth aspect of the present invention, in the high-frequency plasma generating apparatus according to the third aspect, the first standing wave and the second standing wave are generated, and the first and second standing waves are generated. The means for superposing the standing wave includes a pair of electrodes composed of first and second electrodes having a plurality of feeding points, arbitrary pulse modulation is possible, and two output terminals are provided. A first high-frequency power supply capable of arbitrarily setting the phase difference of the output voltage of the output terminal, and first and second impedance matchers connected to the two output terminals of the first high-frequency power supply, respectively. And any pulse modulation synchronized with the pulse modulation signal of the first high-frequency power supply, and two output terminals, and the phase difference between the output voltages of the two output terminals can be arbitrarily set A second high-frequency power source and two output terminals of the second high-frequency power source A third impedance matching device and a fourth impedance matching device connected to each other; and an output terminal of the first impedance matching device is connected to a first feeding point arranged on the first electrode. An output terminal of the second impedance matching device is connected to a second feeding point disposed at a position that is a point opposite to the first feeding point in the propagation of electromagnetic waves, and The third and fourth feed points are arranged one by one at the third and fourth feed points, respectively, arranged at positions parallel to the line segment connecting the first feed point and the second feed point. The output terminal of the impedance matching device is connected.
The invention according to claim 10 of the present application is the high-frequency plasma generator according to claim 3, wherein the first standing wave and the second standing wave are generated, and the first and second standing waves are generated. The means for superposing the standing wave includes a pair of electrodes including a first electrode and a second electrode having a plurality of feeding points, arbitrary pulse modulation is possible, and there are four output terminals and the four outputs. A high-frequency power source capable of arbitrarily setting the phase of the output voltage of the terminal, and first, second, third, and fourth impedance matching units connected one by one to the four output terminals of the high-frequency power source The output terminals of the first and third impedance matching devices are connected to a first feeding point arranged on the first electrode, and electromagnetic waves are transmitted to the first feeding point. 2nd placed at a position that is the opposite point in propagation To a feeding point, and having a structure that the output terminals of the second and the fourth impedance matching is connected.
The invention according to claim 11 of the present application is the high-frequency plasma generator according to claim 3, wherein the first standing wave and the second standing wave are generated, and the first and second standing waves are generated. The means for superposing the standing wave includes a pair of electrodes including a first electrode and a second electrode having a plurality of feeding points, arbitrary pulse modulation is possible, and there are four output terminals and the four outputs. A high-frequency power source capable of arbitrarily setting the phase of the output voltage of the terminal, and first, second, third, and fourth impedance matching units connected one by one to the four output terminals of the high-frequency power source And an output terminal of the first impedance matching device is connected to a first feeding point disposed on the first electrode, and is opposed to the first feeding point in the propagation of electromagnetic waves The second feeding point arranged at a position that is a point is connected to the second feeding point. The output terminals of the impedance matching unit are connected to the third and fourth feeding points arranged at positions parallel to the line segment connecting the first feeding point and the second feeding point. The output terminals of the third and fourth impedance matching units are connected to each other one by one.
The invention described in claim 12 of the present application is the high frequency plasma generator according to any one of claims 8 to 11, wherein the duty ratio of the pulse modulation of the output of the high frequency power source, that is, the pulse width Hw and the period T0. The ratio Hw / T0 is 50% or less.
The invention according to claim 13 of the present application is the high-frequency plasma generator according to any one of claims 2 to 12, wherein the antinode position of the first standing wave and the second standing wave Is 0.22 to 0.28 times, preferably 0.25 times, that is, 0.22 to 0.20 times the wavelength λ of the electromagnetic wave propagating through the generated plasma between the pair of electrodes. It is characterized by having means for setting to 28λ, preferably λ / 4.

The invention according to claim 14 of the present application is the high-frequency plasma generator according to any one of claims 1 to 13, wherein the second electrode has a flat plate shape, and the first electrode Is characterized by having a rectangular or circular flat plate type structure arranged so as to be included in a plane parallel to the second electrode.
The invention according to claim 15 of the present application is the high-frequency plasma generator according to any one of claims 1 to 13, wherein the second electrode has a flat plate shape, and the first electrode Is characterized by having a rod-shaped, U-shaped, W-shaped, or spiral-shaped structure made of rod-shaped conductors arranged in a plane parallel to the second electrode.
The invention according to claim 16 of the present application is the high-frequency plasma generator according to any one of claims 1 to 13, wherein the second electrode has a cylindrical shape, and the first electrode Is characterized by having a bar-shaped, U-shaped, W-shaped, or coil-shaped structure made of a rod-shaped conductor disposed in a cylindrical surface surrounding the second electrode in a mantle shape.
The invention according to claim 17 of the present application is the high-frequency plasma generator according to any one of claims 1 to 13, wherein the first and second electrodes have a plate-like conductor having a plurality of openings. And the substrate is arranged outside the pair of electrodes.

  Further, in the invention described in claim 18 of the present application, the surface of the substrate disposed in the vacuum vessel using the plasma generated by using the power of the output of the high frequency power source whose oscillation frequency belongs to the VHF band or the UHF band. The plasma surface treatment apparatus to be processed is characterized by comprising the high-frequency plasma generation apparatus according to any one of claims 1 to 17.

According to the nineteenth aspect of the present invention, there is provided a substrate surface disposed in a vacuum vessel using plasma generated using an output power of a high frequency power source whose oscillation frequency belongs to a VHF band or a UHF band. In the plasma surface treatment method to be treated, the substrate is subjected to a surface treatment using the high-frequency plasma generator according to any one of claims 1 to 17.
In the invention according to claim 20 of the present application, the surface of the substrate disposed in the vacuum vessel is made using plasma generated using the power of the output of the high frequency power source whose oscillation frequency belongs to the VHF band or the UHF band. In the plasma surface treatment method to be processed, at least a relationship of being an opposing point on the propagation of electromagnetic waves on the surface of the first electrode using the high-frequency plasma generator according to any one of claims 6 and 7 is provided. An output terminal of the first and third impedance matching units is connected to one of the first and second feeding points arranged at two points, and the second and the second feeding points are connected to the second and the second feeding points. The output terminal of the fourth impedance matching device is connected, and the phase difference of the voltage of the power output from the output terminal of the first and second impedance matching devices and the third and fourth inputs The phase difference of the voltage of the electric power output from the output terminal of the impedance matching device is controlled, and the distance between the antinode positions of the two standing waves, that is, the antinode position of the first standing wave and the second constant wave. The distance between the antinodes of the standing wave is 0.22 to 0.28 times, preferably 0.25 times, ie 0.22 times the wavelength λ of the electromagnetic wave propagating through the generated plasma between the pair of electrodes. The surface treatment of the substrate is performed by setting to ˜0.28λ, preferably λ / 4.
In the invention according to claim 21 of the present application, the surface of the substrate disposed in the vacuum vessel is made using plasma generated using the power of the output of the high frequency power source whose oscillation frequency belongs to the VHF band or the UHF band. In the plasma surface treatment method to be processed, at least a relationship of being an opposing point on the propagation of electromagnetic waves on the surface of the first electrode using the high-frequency plasma generator according to any one of claims 8 and 9. An output terminal of the first and third impedance matching units is connected to one of the first and second feeding points arranged at two points, and the first feeding point is connected to the other feeding point. The output terminals of the second and fourth impedance matching devices are connected, and the power output from the first and second output terminals of the first high-frequency power source is represented by a pulse width Hw and a pulse period T0. The half-cycle from the rise time of the pulse-modulated power output from the output terminal of the first high-frequency power source, and the power output from the first and second output terminals of the second high-frequency power source That is, by performing pulse modulation in such a manner that it rises at a time delayed by T0 / 2, the pulse-modulated power output from the first and second output terminals of the first high-frequency power supply and the second high-frequency power supply A time period for supplying pulse-modulated power output from the first and second output terminals to the first and second feeding points is separated, and a first of the first high-frequency power source is separated between the pair of electrodes. And a first standing wave formed by two powers output from the second output terminal and two powers output from the first and second output terminals of the second high-frequency power source. If the time zone of the second standing wave is different, In addition, the phase difference between the power voltages output from the output terminals of the first and second impedance matchers and the phase difference between the power voltages output from the output terminals of the third and fourth impedance matchers And the distance between the antinode positions of the two standing waves, that is, the distance between the antinode position of the first standing wave and the antinode position of the second standing wave is determined between the pair of electrodes. By setting 0.22 to 0.28 times, preferably 0.25 times, that is, 0.22 to 0.28λ, preferably λ / 4, of the wavelength λ of the electromagnetic wave propagating through the generated plasma. A surface treatment of the substrate is performed.
In the invention according to claim 22 of the present application, the surface of the substrate disposed in the vacuum vessel is obtained by using plasma generated by using the power of the output of the high frequency power source whose oscillation frequency belongs to the VHF band or the UHF band. In the plasma surface processing method to process, it is the relationship which becomes an opposing point on the propagation of electromagnetic waves in the said 1st electrode surface using the high frequency plasma generator of any one of Claim 10 or 11. An output terminal of the first and third impedance matching units is connected to one of the first and second feeding points arranged at two points, and the first feeding point is connected to the other feeding point. The output terminals of the second and fourth impedance matching units are connected, and the power output from the first and second output terminals of the high-frequency power source is filtered with a pulse width Hw and a pulse period T0. The power output from the third and fourth output terminals of the high-frequency power source is delayed by a half cycle, that is, T0 / 2 from the rise time of the pal-modulated power output from the first output terminal. By performing pulse modulation so as to rise at time, pulse-modulated power output from the first and second output terminals of the high-frequency power supply and pulses output from the third and fourth output terminals of the high-frequency power supply A time period during which modulated power is supplied to the first and second feeding points is separated, and formed by two powers output from the first and second output terminals of the high-frequency power source between the pair of electrodes. The second standing wave generation time region formed by the first standing wave to be generated and the two electric powers output from the third and fourth output terminals of the high-frequency power source are made different from each other. Of the first and second impedance matchers The phase difference between the voltage of the power output from the power terminal and the voltage phase of the power output from the output terminal of the third and fourth impedance matching devices is controlled, and the antinodes of the two standing waves are controlled. The distance between the positions, that is, the distance between the position of the antinode of the first standing wave and the position of the antinode of the second standing wave is the wavelength λ of the electromagnetic wave propagating inside the generated plasma between the pair of electrodes. The surface treatment of the substrate is performed by setting 0.22 to 0.28 times, preferably 0.25 times, that is, 0.22 to 0.28λ, preferably λ / 4.
The invention according to claim 23 of the present application is the plasma surface treatment method according to any one of claims 20 to 22, wherein the step of grasping the position of the antinode of the first standing wave; The step of grasping the position of the antinode of the second standing wave and the interval between the position of the antinode of the first standing wave and the antinode of the second standing wave are propagated in the generated plasma between the pair of electrodes. A step of performing plasma surface treatment of the substrate by setting to 0.22 to 0.28 times the wavelength λ of the electromagnetic wave, preferably 0.25 times, that is, 0.22 to 0.28λ, preferably λ / 4. Features.

The invention according to claim 24 of the present application is the plasma surface treatment method according to any one of claims 20 to 23, wherein an amorphous Si-based material, a microcrystalline Si-based material, One of a crystalline Si material, a crystalline Si material, an oxide, a metal, an organometallic compound, an organosilicon compound, and an organic compound is formed.
The invention according to claim 25 of the present application is the plasma surface treatment method according to any one of claims 20 to 23, wherein the amorphous Si-based material, the microcrystalline Si-based material fixed to the surface of the substrate, Any one of a polycrystalline Si-based material, a crystalline Si-based material, an oxide, a metal, an organometallic compound, an organosilicon compound, and an organic compound is etched.

According to the plasma generator of claims 1 to 3, the surface of the substrate disposed in the vacuum vessel is made using the plasma generated using the power of the output of the high-frequency power source whose oscillation frequency belongs to the VHF band or the UHF band. In the plasma surface processing apparatus to be processed, it is possible to uniformly control the power intensity distribution between a pair of electrodes, which is indispensable for uniformizing a large area plasma. That is, in the conventional apparatus, it is considered impossible to control the distribution of power intensity between the pair of electrodes, but this is possible. As a result, it is possible to perform a uniform plasma surface treatment with a large area using VHF plasma or UHF plasma targeting a large area substrate, which is considered impossible with conventional apparatuses. That is, it is possible to provide an apparatus capable of realizing a large area and uniform plasma treatment, which is an important issue in the application field of VHF plasma and UHF plasma. The effect is of great value industrially.
According to the plasma generator of claim 4 or 5, it is possible to reliably generate a large-area, uniform, and high-density plasma, and has high application value.
The plasma generators according to claims 6 to 11 are reliable means for realizing the plasma generators according to claims 1 to 5, respectively, and their application value in industry is extremely high. That is, the plasma generators according to claims 6 and 7 can reliably realize the plasma generator according to any of claims 1 to 5 by mainly including two independent two-output phase variable high-frequency power sources. Yes, its practical value is high. Further, the plasma generator according to claims 8 and 9 is capable of performing arbitrary pulse modulation, and has a first high-frequency power source capable of arbitrarily setting a phase difference between two outputs and a voltage of the two outputs. By mainly configuring a second high-frequency power source capable of arbitrary pulse modulation in synchronization with the pulse modulation signal of the high-frequency power source and capable of arbitrarily setting the phase difference between the two output voltages. The plasma generator according to any one of claims 1 to 5 can be reliably realized, and its practical value is high. In addition, the plasma generation apparatus according to claims 10 and 11 is capable of arbitrary pulse modulation, has four output terminals, and can arbitrarily set the phase of the output voltage of the four output terminals. The plasma generator according to any one of claims 1 to 5 can be surely realized, and its practical value is high.
The plasma generator according to claim 12 has a remarkably high value as a reliable means for realizing the plasma generator according to any one of claims 8 to 11.
According to a thirteenth aspect of the present invention, in each of the plasma generators according to the sixth to twelfth aspects, a reliable means for realizing a large-area and uniform plasma is provided. As a result, it is possible to easily realize a large area and uniform surface treatment using VHF plasma or UHF plasma, and its application value in the industry is extremely high.

  The high-frequency plasma generator according to claims 14 to 17 has a remarkably high value as a means for reliably realizing the plasma generators according to claims 6 to 13 for various applications in the industry.

  According to the plasma surface processing apparatus of claim 18, the surface of the substrate disposed in the vacuum vessel is processed using the plasma generated by using the power of the output of the high frequency power source whose oscillation frequency belongs to the VHF band or the UHF band. In the plasma surface treatment apparatus, the power intensity distribution between the pair of electrodes, which is indispensable for uniformizing the large area plasma, can be controlled. As a result, it is possible to perform a uniform plasma surface treatment with a large area using VHF plasma or UHF plasma targeting a large area substrate, which is considered difficult with conventional apparatuses. That is, it is possible to provide an apparatus capable of realizing a large area and uniform plasma treatment, which is an important issue in the application field of VHF plasma and UHF plasma. The effect is of great value industrially.

According to the plasma surface treatment method of claim 19, the surface of the substrate disposed in the vacuum vessel is treated using plasma generated using the power of the output of a high-frequency power source whose oscillation frequency belongs to the VHF band or the UHF band. In the plasma surface treatment method, it is possible to control the distribution of power intensity between a pair of electrodes, which is indispensable for uniformizing a large area plasma. As a result, a large area and uniform plasma surface treatment using VHF plasma or UHF plasma targeting a large area substrate, which is considered difficult by the conventional method, can be performed. That is, it is possible to provide a method capable of realizing a large area and uniform plasma treatment, which is an important issue in the application field of VHF plasma and UHF plasma. The effect is of great value industrially.
The plasma surface treatment method according to any one of claims 20 to 23 is a surface of a substrate disposed in a vacuum vessel using plasma generated by using power of an output of a high frequency power source whose oscillation frequency belongs to a VHF band or a UHF band In the plasma surface treatment method for treating the above, it is possible to reliably realize the uniform control of the power intensity distribution between the pair of electrodes, which is indispensable for uniformizing the large area plasma. As a result, a large area and uniform plasma surface treatment using VHF plasma or UHF plasma targeting a large area substrate, which is considered difficult by the conventional method, can be performed. That is, it is possible to provide a method capable of realizing a large area and uniform plasma treatment, which is an important issue in the application field of VHF plasma and UHF plasma. The effect is of great value industrially.

According to the plasma surface processing method of claim 24, the surface of the substrate disposed in the vacuum vessel is processed using plasma generated using the power of the output of a high frequency power source whose oscillation frequency belongs to the VHF band or the UHF band. In the plasma surface treatment method, an amorphous Si-based material, a microcrystalline Si-based material, a polycrystalline Si-based material, a crystalline Si-based material, an oxide, a metal, an organometallic compound, an organosilicon compound, and an organocompound Any one of the above can be formed uniformly in a large area. As a result, LSIs (Large Scale Integrated Circuits), LCD (Liquid Crystal Display) TFTs (Thin Film Transistors), amorphous Si solar cells, thin film polycrystalline Si solar cells, photoconductors for copying machines, and various information recording devices, etc. A drastic improvement in product productivity in each field is realized. Therefore, the effect is of great value.
According to the plasma surface treatment method of claim 25, the surface of the substrate disposed in the vacuum vessel is treated using plasma generated using the power of the output of a high frequency power source whose oscillation frequency belongs to the VHF band or the UHF band. In a plasma surface treatment method, an amorphous Si-based material, a microcrystalline Si-based material, a polycrystalline Si-based material, a crystalline Si-based material, an oxide, a metal, an organometallic compound, an organosilicon compound, and an organic Any of the compounds can be uniformly etched with a large area. As a result, LSIs (Large Scale Integrated Circuits), LCD (Liquid Crystal Display) TFTs (Thin Film Transistors), amorphous Si solar cells, thin film polycrystalline Si solar cells, photoconductors for copying machines, and various information recording devices, etc. A drastic improvement in product productivity in each field is realized. Therefore, the effect is of great value.

Hereinafter, a high-frequency plasma generator according to an embodiment of the present invention, a plasma surface treatment apparatus constituted by the high-frequency plasma generator, and a plasma surface treatment method will be described with reference to the drawings.
In the following description, as an example of a plasma surface treatment apparatus and a plasma surface treatment method, an apparatus and method for producing an a-Si thin film necessary for producing a solar cell are described. However, the present invention is not limited to the apparatus and method of the following example.

Example 1
Referring to FIGS. 1 to 6, a high-frequency plasma generator of Example 1 relating to the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus will be described. explain. Reference is also made to FIGS.

FIG. 1 is a schematic view showing an entire high-frequency plasma generator according to the first embodiment and a plasma surface treatment apparatus (plasma CVD apparatus) constituted by the high-frequency plasma generator, and FIG. 2 is a structure of the plasma surface treatment apparatus shown in FIG. FIG. 3 is an explanatory diagram showing an electromagnetic wave propagating between a pair of electrodes, and FIG. 4 is an explanatory diagram showing an electromagnetic wave propagating between the pair of electrodes. FIG. 5 is an explanatory diagram showing the position of the antinode of the standing wave of voltage, FIG. 5 is an explanatory diagram showing the strength (value of the square of the amplitude) of the standing wave generated between the pair of electrodes, and FIG. 6 is between the pair of electrodes. It is explanatory drawing which shows the intensity | strength of two standing waves of generation | occurrence | production.
FIG. 7 is an explanatory view showing a first applied type of a configuration related to a pair of electrodes and one of the power supply portions as one of the constituent members of the plasma surface treatment apparatus shown in FIG. 1, and FIG. 8 is a plasma shown in FIG. FIG. 9 is an explanatory view showing a second applied type of a configuration related to a pair of electrodes and one of the power supply portions which are one of the constituent members of the surface treatment apparatus, and FIG. 9 is one of the constituent members of the plasma surface treatment apparatus shown in FIG. It is explanatory drawing which shows the 3rd application type | mold of the structure concerning a pair of electrode which is and its electric power feeding part.

First, the configuration of the apparatus will be described. 1 and 2, reference numeral 1 denotes a vacuum vessel. The vacuum vessel 1 includes a pair of electrodes for converting a discharge gas, which will be described later, into plasma, that is, a first electrode 2 composed of a single non-grounded bar, and a grounded flat plate-like first member including a substrate heater 3 (not shown). Two electrodes 4 are arranged. The first electrode 2 is fixed to the vacuum vessel 1 via an insulator support 5 and a gas mixing box 6.
The gas mixing box 6 has a function of uniformly supplying a discharge gas such as SiH 4 supplied from the discharge gas supply pipe 8 between the pair of electrodes 2 and 4 through the rectifying holes 7. The supplied discharge gas such as SiH 4 is converted into plasma between the pair of electrodes 2 and 4, and then discharged out of the vacuum vessel 1 by the exhaust pipe 9 and a vacuum pump 10 (not shown).

  The pressure in the vacuum vessel 1 is monitored by a pressure gauge (not shown), and is automatically adjusted and set to a predetermined value by a pressure adjustment valve (not shown). In the case of the present embodiment, when the discharge gas has a flow rate of about 500 sccm to 1, 500 sccm, the pressure can be adjusted to about 0.01 Torr to 10 Torr (1.33 Pa to 1330 Pa). The vacuum ultimate pressure of the vacuum vessel 1 is about 2 to 3E-7 Torr (2.66 to 3.99E-5 Pa).

  Reference numeral 11 denotes a substrate, which is installed on the second electrode 4 by opening and closing a gate valve 12 (not shown). Then, it is heated to a predetermined temperature by a substrate heater 3 (not shown).

  One feeding point, which is a position for feeding high-frequency power to the electrode, is one end of the first electrode 2 composed of the one bar, and this is a first feeding point 21. The other end portion of the electrode, which is in a position that is a point opposite to the feeding point 21 in the propagation of a high-frequency power wave, is a second feeding point 27.

Reference numeral 15a is a first phase variable 2-output transmitter which generates a sine wave signal having an arbitrary frequency of 30 MHz to 300 MHz (VHF band) or 300 MHz to 3 GHz (UHF band). A sine wave electrical signal having a frequency of 60 MHz is output from each of the two output terminals. The phase difference between the two sine wave signals output from the two output terminals of the phase variable two-output transmitter 15a can be set to any value using the phase difference adjuster attached to the phase variable two-output transmitter 15a. Can be set. One output of the two output terminals is output via the first power amplifier 16, the first impedance matching device 17, the first current introduction terminal 18, and the core wire 20 of the first vacuum coaxial cable 19. 1 is supplied to one feeding point 21.
It should be noted that the phase variable 2-output transmitter 15a and the first power amplifier 16 are connected, the first power amplifier 16 and the first impedance matcher 17 are connected, and the first impedance matcher 17 and the first power amplifier 16 are connected. A coaxial cable is used for connection to the current introduction terminal 18. The outer conductor of the first vacuum coaxial cable 19 is connected to the second electrode 4.
The other output of the two output terminals of the first phase-variable two-output transmitter 15a is a second power amplifier 22, a second impedance matching unit 23, a second current introduction terminal 24, a second vacuum. It is supplied to the second feeding point 27 through the core wire 26 of the coaxial cable 25 for use.
It should be noted that the phase variable 2-output transmitter 15a is connected to the second power amplifier 22, the second power amplifier 22 is connected to the second impedance matching unit 23, and the second impedance matching unit 23 is connected to the second power amplifier 22. A coaxial cable is used for connection with the current introduction terminal 24. The outer conductor of the second vacuum coaxial cable 25 is connected to the second electrode 4.
Each of the first power amplifier 16 and the second power amplifier 22 is attached with a monitor for an output value (traveling wave) and a monitor for a reflected wave returning from the downstream side. In addition, an isolator for protecting the electric circuit of the first and second power amplifiers 16 and 22 by the reflected wave is attached.
Here, the first phase variable and two-output transmitter 15 a, the first power amplifier 16, the first impedance matching device 17, the first current introduction terminal 18, and the core wire 20 of the first vacuum coaxial cable 19. The power supply system including the second power amplifier 22, the second impedance matching unit 23, the second current introduction terminal 24, and the core wire 26 of the second vacuum coaxial cable 25 is referred to as a first power supply system.

Reference numeral 28a is a second phase variable two-output transmitter independent of the first phase variable two-output transmitter. A wave signal is generated and a sine wave electric signal having a frequency of, for example, 60 MHz is output from the two output terminals. Note that the phase difference between the two sine wave signals output from the two output terminals of the phase-variable two-output transmitter 28a can be set to any value using the phase difference adjuster attached to the phase-variable two-output transmitter 28a. Can be set.
One output of the two output terminals is output via the third power amplifier 29, the third impedance matching device 30, the third current introduction terminal 31, and the core wire 33 of the third vacuum coaxial cable 32. 1 is supplied to one feeding point 21.
It should be noted that the second phase variable 2-output transmitter 28 and the third power amplifier 29 are connected, the third power amplifier 29 and the third impedance matching device 30 are connected, and the third impedance matching device 30 is connected. For the connection with the third current introduction terminal 31, a coaxial cable is used for both. The outer conductor of the third vacuum coaxial cable 32 is connected to the second electrode 4.
The other output of the two output terminals of the second phase variable two-output transmitter 28a is a fourth power amplifier 34, a fourth impedance matcher 35, a fourth current introduction terminal 36, and a fourth vacuum. It is supplied to the second feeding point 27 through the core wire 38 of the coaxial cable 37 for use.
It should be noted that the second phase variable 2-output transmitter 28a and the fourth power amplifier 34 are connected, the fourth power amplifier 34 and the fourth impedance matching device 35 are connected, and the fourth impedance matching device 35 is connected. For the connection with the fourth current introduction terminal 36, a coaxial cable is used in all cases. The outer conductor of the fourth vacuum coaxial cable 37 is connected to the second electrode 4.
Each of the third power amplifier 29 and the fourth power amplifier 34 is accompanied by a monitor for an output value (traveling wave) and a monitor for a reflected wave returning from the downstream side. Further, an isolator for protecting the electric circuit of the third and fourth power amplifiers 29 and 34 by the reflected wave is attached.
Here, the second phase variable two-output transmitter 28a, the third power amplifier 29, the third impedance matching device 30, the third current introduction terminal 31, and the core wire 33 of the third vacuum coaxial cable 32. The power supply system including the fourth power amplifier 34, the fourth impedance matching device 35, the fourth current introduction terminal 36, and the core wire 38 of the fourth vacuum coaxial cable 37 is referred to as a second power supply system. .
Here, the plasma generation system including the first power supply system, the second power supply system, the pair of electrodes 2 and 4 and the feeding points 21 and 27 is referred to as a high-frequency plasma generator.

Next, a method for producing an amorphous Si film for an a-Si solar cell will be described using the high-frequency plasma generator having the above-described configuration and a plasma surface treatment apparatus (plasma CVD apparatus) having the high-frequency plasma generator.
In the implementation or application of the present invention, the first and second preliminary film forming steps and the main film forming step are necessary as procedures. The first preliminary film-forming step is a second preliminary film-forming step in order to obtain data necessary for grasping the set value of the phase difference between the two outputs of the first phase variable two-output transmitter 15a. In order to grasp the set value of the phase difference between the two outputs of the transmitter 28a having the second variable phase and two outputs, this film forming process is carried out for the purpose of manufacturing the target amorphous Si.

First, in the first first preliminary film-forming step, in FIGS. 1 and 2, the substrate 11 is previously set on the second electrode 4, and the vacuum pump 10 (not shown) is operated to operate the vacuum container. After removing the impurity gas and the like in 1, the substrate temperature is in the range of 80 to 350 ° C., for example 180, while the SiH 4 gas is supplied from the discharge gas supply tube 8 at 250 sccm and the pressure 0.5 Torr (66.5 Pa). Hold at ℃.
Next, the first phase variable 2-output transmitter 15a, the first power amplifier 16, the first impedance matching unit 17, the first current introduction terminal 18, and the core wire 20 of the first vacuum coaxial cable 19 are used. A pair of electrodes using a first power supply system comprising a second power amplifier 22, a second impedance matching unit 23, a second current introduction terminal 24, and a core wire 26 of a second vacuum coaxial cable 25. 2 and 4 are supplied with high-frequency power, for example, power with a frequency of 60 MHz, for example, 200 W in total.
That is, the phase difference between the two outputs of the first phase variable and two-output transmitter 15a is set to, for example, zero, the output of the first power amplifier 16 is set to 100 W, and the output is set to the first The impedance matching unit 17, the first current introduction terminal 18, and the core wire 20 of the first vacuum coaxial cable 19 are supplied to the first feeding point 21 and the output of the second power amplifier 22 is set to 100 W. Then, the output is supplied to the second feeding point 27 via the second impedance matching unit 23, the second current introduction terminal 24, and the core wire 26 of the second vacuum coaxial cable 25.
In this case, by adjusting the first impedance matching unit 17 and the second impedance matching unit 23, it is possible to prevent the reflected wave of the supplied power from returning to the upstream side of the respective impedance matching units 17 and 23.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. As will be described later, the film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave, which is a phenomenon inherent to VHF plasma. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 15a having the first phase variable and two outputs as a parameter. Then, in the length direction of the first electrode 2, the distance from the center point of the substrate 11 to the position of the maximum thickness of the sinusoidal film thickness distribution and the two outputs of the transmitter 15 a having the first phase variable 2 output Ascertain the relationship of the phase difference between the two. For example, it is understood that the phase difference for setting a position that is one-eighth of the wavelength λ from the center point of the substrate 11 in the direction of the first feeding point 21, that is, λ / 8, is, for example, Δθ1. Is done.
Note that the method of grasping the relationship between the maximum position of the sinusoidal thickness distribution and the phase difference of the output voltage of the first variable-phase two-output transmitter 15a performed here is the measurement of the thickness distribution of the film. The method is not limited to the application method. For example, the spatial distribution of the emission intensity of the generated plasma in the electromagnetic wave propagation direction is measured with an optical sensor, and the relationship between the position of the maximum intensity and the phase difference is grasped. Also good.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the plasma under the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

By the way, the voltage wave of the power supplied from the first and second feeding points 21 and 27 is oscillated from the same power source and propagates between the electrodes. That is, two electromagnetic waves having an electric field in substantially the same direction as the normal direction of the surface of the substrate 11 are generated between the first electrode 2 and the second electrode 4, and both propagate from directions opposite to each other. Since they overlap each other, an interference phenomenon occurs. This will be described with reference to FIGS.
The direction substantially the same as the normal direction of the surface of the substrate 11 means a direction having a cosine value of 0.7 or more, that is, a direction within about 45 degrees from the normal line.
2 and 3, the distance in the direction from the first feeding point 21 to the second feeding point 27 is x, and the voltage wave propagating in the positive direction of x is W11 (x, t), in the negative direction of x. Assuming that a propagating voltage wave, that is, a voltage wave propagating from the second feeding point 27 toward the first feeding point 21, is W21 (x, t), it is expressed as follows.
W11 (x, t) = V1 · sin (ωt + 2πx / λ)
W21 (x, t) = V1 · sin {ωt−2π (x−L0) / λ + Δθ}
Where V1 is the amplitude of the voltage wave, ω is the angular frequency of the voltage, λ is the wavelength of the voltage wave, t is time, L0 is the interval between the first and second feeding points, and Δθ is supplied from the first feeding point 21. The phase difference between the voltage wave of the electric power and the voltage wave of the electric power supplied from the second feeding point 27. A composite wave W1 (x, t) of these two voltage waves is expressed by the following equation.
W1 (x, t) = W11 (x, t) + W21 (x, t)
= 2 · V1cos {2π (x−L0 / 2) / λ−Δθ / 2} · sin {ωt + (πL0 / λ + Δθ / 2)
The synthesized wave W1 (x, t) is conceptually shown in FIG. In FIG. 4, when Δθ = 0, the intensity of the generated plasma is strong in the central portion (x = L0 / 2) between the feeding points, and decreases as the distance from the central portion increases. The strong plasma portion indicates that when Δθ> 0, the strong plasma portion moves toward one feeding point, and when Δθ <0, the other plasma moves toward the other feeding point.
Here, the voltage waves of the power supplied to the first and second feeding points 21 and 27 using the first power supply system are respectively expressed as W11 (x, t) and W21 (x , T). Further, the combined wave of the two voltage waves is referred to as a first standing wave W1 (x, t).

By the way, the strength of the power between the pair of electrodes is proportional to the square of the amplitude value of the composite wave of the voltage, that is, the first standing wave W1 (x, t). That is, the power intensity I1 (x, t) is
I1 (x, t) ∝cos ² {2π (x−L0 / 2) / λ−Δθ / 2}
It is expressed. This I1 (x, t) is conceptually shown in FIG.
In general, FIG. 5 shows that in the generation of VHF plasma, the plasma between a pair of electrodes is reduced by a standing wave generated by the interference between the traveling wave from the feeding point and the reflected wave from the opposite end of the feeding point. It shows the reason for the difficulty of not being able to. For example, when the power intensity I1 (x, t) is in the range of 0.9 to 1.0, the uniformity of the plasma is in the range of −0.05 to + 0.05λ in terms of the distance in the power propagation direction ( That is, the range in which the film thickness is uniform is limited to a length of 0.1λ).
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the plasma under the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Next, in the second preliminary film forming step, in FIGS. 1 and 2, the substrate 11 is previously set on the second electrode 4, the vacuum pump 10 (not shown) is operated, and the inside of the vacuum container 1 is operated. After removing the impurity gas, etc., the substrate temperature is in the range of 80 to 350 ° C., for example, 180 ° C. while supplying the SiH 4 gas from the discharge gas supply tube 8 at 250 sccm and the pressure of 0.5 Torr (66.5 Pa) Hold.
Then, the second phase variable 2-output transmitter 28a, the third power amplifier 29, the third impedance matching device 30, the third current introduction terminal 31, the core wire 33 of the third vacuum coaxial cable 32, Using the second power supply system comprising the fourth power amplifier 34, the fourth impedance matching device 35, the fourth current introduction terminal 36, and the core wire 38 of the fourth vacuum coaxial cable 37, the pair of electrodes 2 4 is supplied with high frequency power, for example, with a frequency of 60 MHz, for example, 200 W in total.
That is, the phase difference between the two outputs of the second phase variable two-output transmitter 28a is set to, for example, zero, the output of the third power amplifier 29 is set to 100 W, and the output is set to the third output. The impedance matching unit 30, the third current introduction terminal 31, and the core wire 33 of the third vacuum coaxial cable 32 are supplied to the first feeding point 21 and the output of the fourth power amplifier 34 is set to 100 W. Then, the output is supplied to the second feeding point 27 via the fourth impedance matching unit 35, the fourth current introduction terminal 36, and the core wire 38 of the fourth vacuum coaxial cable 37.
In this case, by adjusting the third impedance matching unit 30 and the fourth impedance matching unit 35, the reflected wave of the supplied power can be prevented from returning to the upstream side of the respective impedance matching units 30 and 35.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 has a sinusoidal distribution due to the generation of a standing wave that is a phenomenon inherent to the VHF plasma. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 28a having the second phase variable and two outputs as a parameter. Then, in the length direction of the first electrode 2, the distance from the center point of the substrate to the position of the maximum thickness of the sinusoidal film thickness distribution and the two outputs of the transmitter 28 of the second phase variable two output Understand the relationship of phase difference as data.
Also in this case, as in the first preliminary film forming step, when the second power supply system is used, the distance from the center point of the substrate to the position of the maximum thickness of the sine film thickness distribution and the first The position of the maximum thickness of the film thickness distribution is, for example, the wavelength from the center point of the substrate toward the second feeding point 27 based on the data indicating the relationship between the two output phase differences of the two phase variable and two output transmitters 28a. It can be understood that the phase difference for setting the position to one eighth of λ, that is, a position separated by λ / 8 is, for example, Δθ2.
Note that the method of grasping the relationship between the maximum position of the sinusoidal thickness distribution and the phase difference of the output voltage of the first variable-phase two-output transmitter 15a performed here is the measurement of the thickness distribution of the film. The method is not limited to the application method. For example, the spatial distribution of the emission intensity of the generated plasma in the electromagnetic wave propagation direction is measured with an optical sensor, and the relationship between the position of the maximum intensity and the phase difference is grasped. Also good.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the plasma under the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

In the second preliminary film forming step, the voltage wave of the power supplied from the first and second feeding points 21 and 27 is oscillated from the same power source and propagates between the electrodes. That is, two electromagnetic waves having an electric field in substantially the same direction as the normal direction of the surface of the substrate 11 are generated between the first electrode 2 and the second electrode 4, and both propagate from directions opposite to each other. Since they overlap each other, an interference phenomenon occurs. This will be described with reference to FIGS.
The direction substantially the same as the normal direction of the surface of the substrate 11 means a direction having a cosine value of 0.7 or more, that is, a direction within about 45 degrees from the normal line.
2 and 3, the distance in the direction from the first feeding point 21 to the second feeding point 27 is x, and the voltage wave propagating in the positive direction of x is W12 (x, t), in the negative direction of x. Assuming that a propagating voltage wave, that is, a voltage wave propagating from the second feeding point 27 to the first feeding point 21 is W22 (x, t), it is expressed as follows.
W12 (x, t) = V2 · sin (ωt + 2πx / λ)
W22 (x, t) = V2 · sin {ωt−2π (x−L0) / λ + Δθ}
Where V2 is the amplitude of the voltage wave, ω is the angular frequency of the voltage, λ is the wavelength of the voltage wave, t is the time, L0 is the interval between the first and second feed points, and Δθ is supplied from the first feed point 21. The phase difference between the voltage wave of the electric power and the voltage wave of the electric power supplied from the second feeding point 27 The voltage composite wave W2 (x, t) is expressed by the following equation.
W2 (x, t) = W12 (x, t) + W22 (x, t)
= 2 · V2cos {2π (x−L0 / 2) / λ−Δθ / 2} · sin {ωt + (πL0 / λ + Δθ / 2)
The synthetic wave W2 (x, t) is conceptually shown in FIG. In FIG. 4, when Δθ = 0, the intensity of the generated plasma is strong in the central portion (x = L0 / 2) between the feeding points, and decreases as the distance from the central portion increases. The strong plasma portion indicates that when Δθ> 0, the strong plasma portion moves toward one feeding point, and when Δθ <0, the other plasma moves toward the other feeding point.
Here, the voltage waves of the power supplied to the first and second feeding points 21 and 27 using the second power supply system are respectively expressed as W12 (x, t) and W22 (x, t). The combined wave of the two waves is called a second standing wave W2 (x, t).

By the way, the strength of the power between the pair of electrodes is proportional to the square of the amplitude value of the second standing wave W2 (x, t). That is, the power intensity I2 (x, t) is
I2 (x, t) ∝cos ² {2π (x−L0 / 2) / λ−Δθ / 2}
It is expressed. This I2 (x, t) is conceptually shown in FIG.
In general, FIG. 5 shows that in the generation of VHF plasma, the plasma between a pair of electrodes is reduced by a standing wave generated by the interference between the traveling wave from the feeding point and the reflected wave from the opposite end of the feeding point. It shows the reason for the difficulty of not being able to. For example, when the power intensity I1 (x, t) is in the range of 0.9 to 1.0, the uniformity of the plasma is in the range of −0.05 to + 0.05λ in terms of the distance in the power propagation direction ( That is, the range in which the film thickness is uniform is limited to a length of 0.1λ).
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the plasma under the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Now, in response to the results of the first and second preliminary film forming steps, the main film forming step is started. First, in FIGS. 1 and 2, the substrate 11 is previously set on the second electrode 4, the vacuum pump 10 (not shown) is operated to remove the impurity gas in the vacuum vessel 1, and then the discharge gas is supplied. While supplying SiH4 gas from the tube 8 at, for example, 300 sccm and a pressure of 0.5 Torr (66.5 Pa), the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C.
Next, the phase difference between the two outputs of the first phase variable and two-output transmitter 15a of the constituent members of the first power supply system is set to Δθ1 grasped as data of the first preliminary film forming step. For example, 100 W of 60 MHz is supplied to the first and second feeding points 21 and 27, respectively, and the second phase-variable 2-output transmitter 28a of the constituent member of the second power supply system 2 The phase difference between the two outputs is set to Δθ2 grasped as data of the second preliminary film-forming process, and 100 W of 60 MHz, for example, is supplied to the first and second feeding points 21 and 27, respectively. That is, the voltage waves W11 (x, t), W21 (x, t), W12 (x, t) and W22 (x, t) are supplied to the first and second feeding points 21 and 27. .
Here, the first impedance matching unit 17, the second impedance matching unit 23, the third impedance matching unit 30, and the fourth that were not problematic in the first preliminary film forming step and the second preliminary film forming step. If the impedance adjustment of the impedance matching unit 35 is not successful, the oscillation frequency of one of the first or second variable phase two output transmitters 15a and 28a is changed to a value slightly different from the other oscillation frequency. do it. For example, in the above example, 60 MHz and 61 to 63 MHz, for example, 62 MHz may be used. The reason why the matching of the impedance matching unit is not well adjusted is often due to restrictions on the performance of the components used, that is, on the function of the anti-reflection wave of the power amplifier on the upstream side of the impedance matching unit.

When four voltage waves are supplied between the pair of electrodes 2, 4, as described above, W 11 (x, t) and W 21 (x, t) interfere with each other and the first standing wave W 1 (x, t t), and W12 (x, t) and W22 (x, t) interfere to form a second standing wave W2 (x, t). However, since the first and second phase variable two-output transmitters 15a and 28a are independent power supplies, W11 (x, t) does not interfere with W12 (x, t) and W22 (x, t). Similarly, W21 (x, t) does not interfere with W12 (x, t) and W22 (x, t).
It is important that the first and second phase variable two-output transmitters 15a and 28a are independent power sources.
Therefore, the intensity distribution of the power generated between the pair of electrodes 2 and 4 is the intensity distribution I1 (x, t) of the first standing wave W1 (x, t) and the second standing wave. The intensity distribution I2 (x, t) of the wave W2 (x, t) is superimposed. This is conceptually shown in FIG.
Here, if the center point of the substrate is the origin of the x-axis and the direction from the origin toward the first feeding point 21 is a positive direction, the strength of the first standing wave W1 (x, t) Distribution I1 (x, t) is
I1 (x, t) ∝cos ² {2πx / 2 + 2π (λ / 8) / λ}
= Cos ² {2πx / 2 + π / 4}
The intensity distribution I2 (x, t) of the second standing wave W2 (x, t) is
I2 (x, t) ∝cos ² {2πx / 2-2π (λ / 8) / λ}
= Cos ² {2πx / 2−π / 4}
The distribution I (x, t) of the strength of power generated between the pair of electrodes 2 and 4 is
I (x, t)
= Cos ² {2πx / 2 + π / 4} + cos ² {2πx / 2−π / 4}
= 1

As a result, the high frequency used in the surface treatment apparatus for treating the surface of the substrate disposed in the vacuum vessel using the plasma generated using the power of the output of the high frequency power source whose oscillation frequency belongs to the VHF band or the UHF band. In the plasma generator, a first standing wave and a second standing wave are generated in which the positions of antinodes of the standing wave of the electromagnetic wave having an electric field substantially in the same direction as the normal direction of the surface of the substrate are different. In addition, the provision of means for superimposing the first and second standing waves makes it possible to control the distribution of power intensity between the electrodes, which is indispensable for plasma uniformity. .
Further, if the distance between the antinodes of the first and second standing waves is 0.25 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.25λ, a pair of electrodes The power intensity distribution I (x, t) generated between 2 and 4 has a constant value and does not depend on the position in the power propagation direction, and is uniform. This means that it is an epoch-making discovery in the sense that it is possible to provide an apparatus capable of realizing large-area and uniform plasma processing, which is an important issue in the application field of UHF plasma and UHF plasma. Yes.
The distance between the antinodes of the first and second standing waves is 0.22 to 0.28 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.22 to 0.2. If it is 28λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 20% or less.
The distance between the antinodes of the first and second standing waves is 0.238 to 0.263 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.238 to. In the case of H.263λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 10% or less.

In the above process, when SiH 4 gas is turned into plasma, radicals such as SiH 3, SiH 2, and SiH existing in the plasma diffuse due to a diffusion phenomenon and are adsorbed on the surface of the substrate 11, thereby depositing an a-Si film. However, since the power distribution between the pair of electrodes 2 and 4 is uniform as described above, the deposited film becomes uniform.
This means that it is possible to achieve a uniform film thickness distribution that is impossible with the conventional VHF plasma surface treatment apparatus and method for a substrate having a size exceeding one-half of the wavelength λ. Means. Therefore, the above is an epoch-making discovery in the VHF plasma and UHF plasma application fields, and its practical value is remarkably great.

It is a well-known technique that microcrystalline Si, thin-film polycrystalline Si, or the like can be formed by optimizing the flow ratio, pressure, and power of SiH4 and H2 in the film forming conditions.
In addition, it is a known technique that can be applied to etching by using NF3, SF6, CF4, CHF3, C4F4, or the like as a discharge gas.

In this embodiment, since the first electrode 2 is a single bar, the substrate size is limited to the above-mentioned 1200 mm × 100 mm. However, if the number of the rod electrodes as the first electrode 2 is increased, the width of the substrate size is increased. Of course, it is expandable.

Further, in the manufacture of a-Si solar cells, thin film transistors, and photosensitive drums, there is no problem in performance as long as the film thickness distribution is within ± 10%. According to the above embodiment, it is possible to obtain a remarkably good film thickness distribution as compared with the conventional apparatus and method even when a power supply frequency of 60 MHz is used.
This means that a plasma surface treatment apparatus using a frequency in the VHF band or the UHF band as a means of drastic improvement in terms of productivity and cost reduction in the manufacturing field of a-Si solar cells, thin film transistors, and photosensitive drums. Means that it can be provided. The industrial value of this effect is significantly great.

Here, the pair of electrodes 2 and 4 having the structure shown in FIG. 2 which is one of the components of the apparatus of the present embodiment is replaced with the pair of electrodes 2 and 4 shown in FIG. It should be noted that the same plasma treatment as in this embodiment can be performed by using a plasma surface treatment apparatus instead of the pair of electrodes composed of 2 and the plate electrode 4.
In this case, as compared with the plasma generated by a pair of electrodes composed of the rod-shaped electrode 2 and the plate electrode 4 in FIG. 2, there is an advantage that it is possible to easily generate plasma having a spread in a direction perpendicular to the propagation direction of electromagnetic waves. is there.

Further, the pair of electrodes 2 and 4 having the structure shown in FIG. 2 which is one of the components of the apparatus of this embodiment is replaced with the pair of electrodes 2 and 4 having the structure shown in FIG. It should be noted that the same plasma treatment as in this embodiment can be performed by using a plasma surface treatment apparatus instead of the pair of electrodes composed of the electrode 2 and the plate electrode 4. Note that the line segment connecting the first power supply point 21a and the second power supply point 27a shown in FIG. 8 and the line segment connecting the third power supply point 21b and the fourth power supply point 27b need to be parallel. It is natural.
In this case, as compared with the plasma generated by the pair of electrodes composed of the rod-shaped electrode 2 and the plate electrode 4 shown in FIG. 2, it is possible to easily generate plasma that spreads in a direction perpendicular to the propagation direction of the electromagnetic wave. In addition to the above, there is an advantage that it is possible to distribute the power supplied to the feeding point. That is, it has a feature that it can be applied to plasma processing applications that require high power.

Further, a plasma surface treatment apparatus is used in which the pair of electrodes 2 and 4 having the structure shown in FIG. 2, which is one of the components of the apparatus of this embodiment, is replaced with the rod-like electrodes 2a and 2b having the structure shown in FIG. Note that the same plasma treatment as in this embodiment can be performed.
The first rod-like electrode 2a and the second rod-like electrode 2b shown in FIG. 9 need to be installed in parallel.
In this case, there is an advantage that it is possible to disperse the electric power supplied to the feeding point as compared with the plasma generated by the pair of electrodes composed of the rod-like electrode 2 and the plate electrode 4 shown in FIG. That is, it has a feature that it can be applied to plasma processing applications that require high power.
Further, in the above description, in the description of the generation of the standing wave of the electromagnetic wave using the high-frequency plasma generator according to the embodiment of the present invention and the plasma surface treatment apparatus constituted by the high-frequency plasma generator, the standing Although the number of waves is mainly described in the case of two, increasing the number to two or more can be easily performed by arranging a large number of feeding points.

(Example 2)
A high-frequency plasma generator of Example 2 relating to the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus are described with reference to FIGS. explain. Reference is also made to FIGS.
FIG. 10 is a schematic diagram showing an entire high-frequency plasma generator according to the second embodiment and a plasma surface treatment apparatus (plasma CVD apparatus) constituted by the high-frequency plasma generator, and FIG. 11 shows first and second pulse modulation system phases. FIG. 12 is a diagram illustrating a typical example of pulse-modulated output output from a variable two-output oscillator, and FIG. 12 is a pulse-modulated sine output from first and second pulse modulation type phase-variable two-output oscillators. It is explanatory drawing which shows the typical example of a wave signal.

First, the configuration of the apparatus will be described. However, the same members as those shown in the first embodiment are denoted by the same reference numerals and description thereof is omitted.
The first and second phase variable two-output transmitters 15a and 28a in the device configuration (Embodiment 1) shown in FIG. 1 and FIG. It is characterized in that the phase variable 2 output transmitter 15 and the second pulse modulation type phase variable 2 output transmitter 28 are replaced.

In FIG. 10, reference numeral 100 denotes a synchronization signal transmission cable, which uses a pulse modulation waveform signal output from a first pulse modulation method variable phase two-output transmitter 15 described later as a synchronization signal and a second pulse modulation method phase described later. Transmit to the variable two-output transmitter 28.
Reference numeral 15 is a first pulse modulation type phase variable 2-output transmitter, which generates a sine wave signal having an arbitrary frequency of 30 MHz to 300 MHz (VHF band) or 300 MHz to 3 GHz (UHF band), for example, 60 MHz, In addition, the sine wave signal can be pulse-modulated, and the phase difference between the two pulse-modulated sine wave signals output from the two output terminals can be arbitrarily set.
The phase difference between the two sine wave signals output from the two output terminals of the pulse modulation type phase-variable two-output transmitter 15 and the pulse width Hw and period T0 of the pulse modulation are the same as those of the pulse modulation type phase-variable two-output. The phase difference adjuster and the pulse modulation adjuster attached to the transmitter 15 can be set to arbitrary values.
Further, the first pulse modulation system variable phase 2 output transmitter 15 transmits a pulse modulation to a second pulse modulation system variable phase 2 output transmitter 28 to be described later via the synchronization signal transmission cable 100 described above. Send a sync signal.
One output of two output terminals of the first pulse modulation type phase variable two-output transmitter 15 is a first power amplifier 16, a first impedance matching unit 17, a first current introduction terminal 18, 1 is supplied to the first feeding point 21 via the core wire 20 of the vacuum coaxial cable 19. As a typical example, this output is a sine wave pulse-modulated with a pulse width Hw and a period T0 as W11 (t) shown in FIGS.
In addition, the connection between the transmitter 15 having the variable phase 2 output and the first power amplifier 16, the connection between the first power amplifier 16 and the first impedance matching unit 17, the first impedance matching unit 17 and the first power matching unit 17 A coaxial cable is used for connection to the current introduction terminal 18. The outer conductor of the first vacuum coaxial cable 19 is connected to the second electrode 4.
The other output of the two output terminals of the first pulse modulation type phase-variable two-output transmitter 15 is a second power amplifier 22, a second impedance matcher 23, a second current introduction terminal 24, a second 2 is supplied to the second feeding point 27 through the core wire 26 of the vacuum coaxial cable 25. This output is a sine wave that is pulse-modulated with the same pulse width Hw and period T0 as W11 (t), as shown in FIG. 11 and FIG. 12 as a typical example.
It should be noted that the phase variable 2-output transmitter 15 and the second power amplifier 22 are connected, the second power amplifier 22 and the second impedance matcher 23 are connected, and the second impedance matcher 23 and the second power amplifier 22 are connected. A coaxial cable is used for connection with the current introduction terminal 24. The outer conductor of the second vacuum coaxial cable 25 is connected to the second electrode 4.
Each of the first power amplifier 16 and the second power amplifier 22 is attached with a monitor for an output value (traveling wave) and a monitor for a reflected wave returning from the downstream side. In addition, an isolator for protecting the electric circuit of the first and second power amplifiers 16 and 22 by the reflected wave is attached.
Here, the first pulse modulation type phase-variable two-output transmitter 15, the first power amplifier 16, the first impedance matching device 17, the first current introduction terminal 18, and the first vacuum coaxial cable 19. The power supply system comprising the core wire 20, the second power amplifier 22, the second impedance matching unit 23, the second current introduction terminal 24, and the core wire 26 of the second vacuum coaxial cable 25 is a first power supply system. Call it.

Reference numeral 28 is a second pulse modulation type phase variable 2-output transmitter which generates a sine wave signal having an arbitrary frequency of 30 MHz to 300 MHz (VHF band) or 300 MHz to 3 GHz (UHF band). A sine wave signal having an arbitrary frequency, for example, 60 MHz, is generated from the two output terminals, and the two sine wave signals are synchronized from the first pulse modulation type phase-variable two-output transmitter 15. By using the synchronization signal received via the signal transmission cable 100, a pulse-modulated signal is output in synchronism with the pulse modulation signal of the first pulse modulation method phase variable 2-output transmitter 15.
The phase difference between the two sine wave signals output from the two output terminals of the pulse modulation type phase variable two-output transmitter 28, the pulse width Hw and the period T0 of the pulse modulation are the transmitter 28 of the phase variable two output. The phase difference adjuster and the pulse modulation adjuster attached to each can be set to arbitrary values.
One output of the two output terminals of the second pulse modulation type phase-variable two-output transmitter 28 includes a third power amplifier 29, a third impedance matching unit 30, a third current introduction terminal 31, and a second output terminal. 3 is supplied to the first feeding point 21 via the core wire 33 of the vacuum coaxial cable 3. As a typical example, this output has a pulse width Hw, a period T0, and the pulse rise time of the pulse modulation of W11 (t) and W21 (t) as shown in W12 (t) shown in FIGS. It is a pulse-modulated sine wave that rises at a half cycle, that is, a time delayed by T0 / 2.
It should be noted that the second phase variable 2-output transmitter 28 and the third power amplifier 29 are connected, the third power amplifier 29 and the third impedance matching device 30 are connected, and the third impedance matching device 30 is connected. For the connection with the third current introduction terminal 31, a coaxial cable is used for both. The outer conductor of the third vacuum coaxial cable 32 is connected to the second electrode 4.
The other output of the two output terminals of the second pulse modulation type phase-variable two-output transmitter 28 includes a fourth power amplifier 34, a fourth impedance matching unit 35, a fourth current introduction terminal 36, 4 is supplied to the second feeding point 27 via the core wire 38 of the vacuum coaxial cable 37. As a typical example, this output has a pulse width Hw, a period T0, and the pulse rise time of the pulse modulation of W11 (t) and W21 (t) as shown in W22 (t) shown in FIGS. It is a pulse-modulated sine wave that rises at a half cycle, that is, a time delayed by T0 / 2.
It should be noted that the second phase variable 2-output transmitter 28 and the fourth power amplifier 34 are connected, the fourth power amplifier 34 and the fourth impedance matching device 35 are connected, and the fourth impedance matching device 35 is connected. For the connection with the fourth current introduction terminal 36, a coaxial cable is used in all cases. The outer conductor of the fourth vacuum coaxial cable 37 is connected to the second electrode 4.
Each of the third power amplifier 29 and the fourth power amplifier 34 is accompanied by a monitor for an output value (traveling wave) and a monitor for a reflected wave returning from the downstream side. Further, an isolator for protecting the electric circuit of the third and fourth power amplifiers 29 and 34 by the reflected wave is attached.
Here, the second pulse modulation type phase-variable two-output transmitter 28, the third power amplifier 29, the third impedance matching device 30, the third current introduction terminal 31, and the third vacuum coaxial cable 32. A power supply system comprising a core wire 33 of the first core wire 33, a fourth power amplifier 34, a fourth impedance matching device 35, a fourth current introduction terminal 36, and a fourth vacuum coaxial cable 37 is a second power supply system. Call it.
Here, the plasma generation system including the first power supply system, the second power supply system, the pair of electrodes 2 and 4 and the feeding points 21 and 27 is referred to as a high-frequency plasma generator.

Next, a method of forming amorphous Si for an a-Si solar cell using the high-frequency plasma generator configured as described above and a plasma surface treatment apparatus (plasma CVD apparatus) configured by the high-frequency plasma generator will be described.
In the implementation or application of the present invention, the first and second preliminary film forming steps and the main film forming step are necessary as procedures. The first preliminary film forming step includes the step of determining the phase difference between the two outputs of the first pulse modulation type phase-variable two-output transmitter 15 in order to grasp the set value of the phase difference between the two outputs. In order to grasp the set value of the phase difference between the two outputs of the second pulse modulation type phase-variable two-output transmitter 28, this film-forming step is performed for the production of the target amorphous Si.

First, in the first first preliminary film-forming step, in FIGS. 10 and 2, the substrate 11 is previously set on the second electrode 4 and the vacuum pump 10 (not shown) is operated to operate the vacuum container. After removing the impurity gas and the like in 1, the substrate temperature is in the range of 80 to 350 ° C., for example 180, while SiH 4 gas is supplied from the discharge gas supply tube 8 at 250 sccm and pressure 0.5 Torr (66.5 Pa), for example. Hold at ° C.
Next, the first pulse modulation type phase-variable two-output transmitter 15, the first power amplifier 16, the first impedance matching unit 17, the first current introduction terminal 18, and the first vacuum coaxial cable 19. A first power supply system comprising a core wire 20, a second power amplifier 22, a second impedance matching unit 23, a second current introduction terminal 24, and a core wire 26 of a second vacuum coaxial cable 25, High frequency power is supplied to the pair of electrodes 2 and 4, for example, with a frequency of 60 MHz, a pulse width Hw = 400 μsec, and a pulse period T0 = 1 msec, for example, 200 W in total.
That is, the phase difference between the two outputs of the first pulse modulation type phase-variable two-output transmitter 15 is set to, for example, zero, the pulse width Hw = 400 μsec, and the pulse period T0 = 1 msec. The output of the power amplifier 16 is set to 100 W, and the output is supplied to the first power supply via the first impedance matching unit 17, the first current introduction terminal 18, and the core wire 20 of the first vacuum coaxial cable 19. In addition to being supplied to the point 21, the output of the second power amplifier 22 is set to 100 W, and the output is supplied to the second impedance matching unit 23, the second current introduction terminal 24, and the second coaxial coaxial cable 25. A second feeding point 27 is supplied via the core wire 26.
In this case, by adjusting the first impedance matching unit 17 and the second impedance matching unit 23, the reflected wave of the supplied power does not return to the upstream side of the respective impedance matching units 17 and 23. Can do.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 15 having the first pulse modulation type variable phase two output as a parameter. Then, in the length direction of the first electrode 2, the distance from the center point of the substrate 11 to the position of the maximum thickness of the sinusoidal film thickness distribution and the transmitter 15 of the first pulse modulation type phase variable 2 output The relationship between the phase differences between the two outputs is grasped as data. For example, it is understood that the phase difference for setting a position that is one-eighth of the wavelength λ from the center point of the substrate 11 in the direction of the first feeding point 21, that is, λ / 8, is, for example, Δθ1. Is done.
Note that the method of grasping the relationship between the maximum position of the sinusoidal thickness distribution and the phase difference of the output voltage of the first variable-phase two-output transmitter 15a performed here is the measurement of the thickness distribution of the film. The method is not limited to the application method. For example, the spatial distribution of the emission intensity of the generated plasma in the electromagnetic wave propagation direction is measured with an optical sensor, and the relationship between the position of the maximum intensity and the phase difference is grasped. Also good.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

By the way, the voltage wave of the power supplied in a pulse form from the first and second feeding points 21 and 27 is oscillated from the same power source and propagates between the electrodes. That is, two electromagnetic waves having an electric field in substantially the same direction as the normal direction of the surface of the substrate 11 are generated between the first electrode 2 and the second electrode 4, and both propagate from directions opposite to each other. Since they overlap each other, an interference phenomenon occurs. This will be described with reference to FIGS.
The direction substantially the same as the normal direction of the surface of the substrate 11 means a direction having a cosine value of 0.7 or more, that is, a direction of about ± 45 degrees from the normal line.
2 and 3, the distance in the direction from the first feeding point 21 to the second feeding point 27 is x, and the voltage wave propagating in the positive direction of x is W11 (x, t), in the negative direction of x. Assuming that a propagating voltage wave, that is, a voltage wave propagating from the second feeding point 27 toward the first feeding point 21, is W21 (x, t), it is expressed as follows.
W11 (x, t) = V1 · sin (ωt + 2πx / λ)
W21 (x, t) = V1 · sin {ωt−2π (x−L0) / λ + Δθ}
Where V1 is the amplitude of the voltage wave, ω is the angular frequency of the voltage, λ is the wavelength of the voltage wave, t is time, L0 is the interval between the first and second feeding points, and Δθ is supplied from the first feeding point 21. The phase difference between the voltage wave of the electric power and the voltage wave of the electric power supplied from the second feeding point 27. A composite wave W1 (x, t) of these two voltage waves is expressed by the following equation.
W1 (x, t) = W11 (x, t) + W21 (x, t)
= 2 · V1cos {2π (x−L0 / 2) / λ−Δθ / 2} · sin {ωt + (πL0 / λ + Δθ / 2)
The synthesized wave W1 (x, t) is conceptually shown in FIG. In FIG. 4, when Δθ = 0, the intensity of the generated plasma is strong in the central portion (x = L0 / 2) between the feeding points, and decreases as the distance from the central portion increases. When Δθ> 0, the strong plasma portion moves to one feeding point side, and when Δθ <0, it moves to the other feeding point side.
Here, the voltage waves of the power supplied to the first and second feeding points 21 and 27 using the first power supply system are respectively expressed as W11 (x, t) and W21 (x , T). Further, the combined wave of the two voltage waves is referred to as a first standing wave W1 (x, t).

By the way, the strength of power between the pair of electrodes is proportional to the square of the amplitude value of the first standing wave W1 (x, t) of the voltage. That is, the power intensity I1 (x, t) is
I1 (x, t) ∝cos ² {2π (x−L0 / 2) / λ−Δθ / 2}
It is expressed. This I1 (x, t) is conceptually shown in FIG.
In general, FIG. 5 shows that in the generation of VHF plasma, the plasma between a pair of electrodes is reduced by a standing wave generated by the interference between the traveling wave from the feeding point and the reflected wave from the opposite end of the feeding point. It shows the reason for the difficulty of not being able to. For example, when the power intensity I1 (x, t) is in the range of 0.9 to 1.0, the uniformity of the plasma is in the range of −0.05 to + 0.05λ in terms of the distance in the power propagation direction ( That is, the range in which the film thickness is uniform is limited to a length of 0.1λ).
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Next, in the second preliminary film forming step, in FIGS. 10 and 2, the substrate 11 is previously set on the second electrode 4, the vacuum pump 10 (not shown) is operated, and the inside of the vacuum container 1 is operated. After removing the impurity gas, etc., the substrate temperature is in the range of 80 to 350 ° C., for example, 180 ° C. while supplying the SiH 4 gas from the discharge gas supply tube 8 at 250 sccm and the pressure of 0.5 Torr (66.5 Pa), for example. Hold.
The second pulse modulation type phase-variable two-output transmitter 28, the third power amplifier 29, the third impedance matching device 30, the third current introduction terminal 31, and the third vacuum coaxial cable 32 Using a second power supply system comprising a core wire 33, a fourth power amplifier 34, a fourth impedance matching device 35, a fourth current introduction terminal 36, and a core wire 38 of a fourth vacuum coaxial cable 37, a pair The electrodes 2 and 4 are supplied with high frequency power, for example, with a frequency of 60 MHz, a pulse width Hw = 400 μsec, and a pulse period T0 = 1 msec, for example, 200 W in total.
That is, the phase difference between the two outputs of the second pulse modulation method phase variable 2-output transmitter 28 is set to, for example, zero, the pulse width Hw = 400 μsec, and the pulse period T0 = 1 msec. The output of the power amplifier 29 is set to 100 W, and the output is supplied to the first power supply via the third impedance matching device 30, the third current introduction terminal 31, and the core wire 33 of the third vacuum coaxial cable 32. The output of the fourth power amplifier 34 is set to 100 W while being supplied to the point 21, and the output of the fourth impedance matching unit 35, the fourth current introduction terminal 36, and the fourth vacuum coaxial cable 37 is set. This is supplied to the second feeding point 27 through the core wire 38.
In this case, by adjusting the third impedance matching unit 30 and the fourth impedance matching unit 35, the reflected wave of the supplied power can be prevented from returning to the upstream side of the respective impedance matching units 30 and 35.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 has a sinusoidal distribution due to the generation of a standing wave that is a phenomenon inherent to the VHF plasma. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 28 of the second pulse modulation type variable phase output 2 as a parameter. Then, in the length direction of the first electrode, the distance from the center point of the substrate to the position of the maximum thickness of the sinusoidal film thickness distribution and the two transmitters 28 of the second pulse modulation type phase variable two output Grasp the relationship of output phase difference as data.
Also in this case, similarly to the first preliminary film forming step, in the case where the second power supply system is used, the distance from the center point of the substrate to the position of the maximum thickness of the sinusoidal film thickness distribution and the first The position of the maximum thickness of the film thickness distribution, for example, from the center point of the substrate to the second feeding point 27 is obtained from data indicating the relationship between the two output phase differences of the two pulse modulation type phase-variable two-output transmitters 28. It can be seen that the phase difference for setting the position to one-eighth of the wavelength λ in the direction, that is, the position separated by λ / 8 is, for example, Δθ2.
Note that the method of grasping the relationship between the maximum position of the sinusoidal thickness distribution and the phase difference of the output voltage of the first variable-phase two-output transmitter 15a performed here is the measurement of the thickness distribution of the film. The method is not limited to the application method. For example, the spatial distribution of the emission intensity of the generated plasma in the electromagnetic wave propagation direction is measured with an optical sensor, and the relationship between the position of the maximum intensity and the phase difference is grasped. Also good.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

In the second preliminary film forming step, the voltage wave of the power supplied from the first and second feeding points 21 and 27 is oscillated from the same power source and propagates between the electrodes. That is, two electromagnetic waves having an electric field in substantially the same direction as the normal direction of the surface of the substrate 11 are generated between the first electrode 2 and the second electrode 4, and both propagate from directions opposite to each other. Since they overlap each other, an interference phenomenon occurs. This will be described with reference to FIGS.
The direction substantially the same as the normal direction of the surface of the substrate 11 means a direction having a cosine value of 0.7 or more, that is, a direction within about 45 degrees from the normal line.
2 and 3, the distance from the first feeding point 21 to the second feeding point 27 is x, and the voltage wave propagating in the positive x direction is W12 (x, t), in the negative x direction. Assuming that a propagating voltage wave, that is, a voltage wave propagating from the second feeding point 27 toward the first feeding point 21, is W22 (x, t), it is expressed as follows.
W12 (x, t) = V2 · sin (ωt + 2πx / λ)
W22 (x, t) = V2 · sin {ωt−2π (x−L0) / λ + Δθ}
Where V2 is the amplitude of the voltage wave, ω is the angular frequency of the voltage, λ is the wavelength of the voltage wave, t is the time, L0 is the interval between the first and second feed points, and Δθ is supplied from the first feed point 21. The phase difference between the voltage wave of the electric power and the voltage wave of the electric power supplied from the second feeding point 27 The voltage composite wave W2 (x, t) is expressed by the following equation.
W2 (x, t) = W12 (x, t) + W22 (x, t)
= 2 · V2cos {2π (x−L0 / 2) / λ−Δθ / 2} · sin {ωt + (πL0 / λ + Δθ / 2)
The synthetic wave W2 (x, t) is conceptually shown in FIG. In FIG. 4, when Δθ = 0, the intensity of the generated plasma is strong in the central portion (x = L0 / 2) between the feeding points, and decreases as the distance from the central portion increases. When Δθ> 0, the strong plasma portion moves to one feeding point side, and when Δθ <0, it moves to the other feeding point side.
Here, the voltage waves of the power supplied to the first and second feeding points 21 and 27 using the second power supply system are respectively expressed as W12 (x, t) and W22 (x, t). The combined wave of the two waves is called a second standing wave W2 (x, t).

By the way, the strength of the power between the pair of electrodes is proportional to the square of the amplitude value of the composite wave W2 (x, t) of the voltage. That is, the power intensity I2 (x, t) is
I2 (x, t) ∝cos ² {2π (x−L0 / 2) / λ−Δθ / 2}
It is expressed. This I2 (x, t) is conceptually shown in FIG.
In general, FIG. 5 shows that in the generation of VHF plasma, the plasma between a pair of electrodes is reduced by a standing wave generated by the interference between the traveling wave from the feeding point and the reflected wave from the opposite end of the feeding point. It shows the reason for the difficulty of not being able to. For example, when the power intensity I1 (x, t) is in the range of 0.9 to 1.0, the uniformity of the plasma is in the range of −0.05 to + 0.05λ in terms of the distance in the power propagation direction ( That is, the range in which the film thickness is uniform is limited to a length of 0.1λ).
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Now, in response to the results of the first and second preliminary film forming steps, the main film forming step is started. First, in FIG. 10 and FIG. 2, the substrate 11 is set on the second electrode 4 in advance, the vacuum pump 10 (not shown) is operated, the impurity gas in the vacuum vessel 1 is removed, and the discharge gas is supplied. While supplying SiH4 gas from the tube 8 at, for example, 300 sccm and a pressure of 0.5 Torr (66.5 Pa), the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C.
Next, the phase difference between the voltages of the two outputs of the transmitter 15 of the first pulse modulation method variable phase output 2 of the component of the first power supply system was grasped as data of the first preliminary film forming process. Δθ1 is set, and the pulse modulation is set such that the pulse width Hw and the period T0 in W11 (t) and W21 (t) shown in FIGS. 3 and 4 are set to, for example, Hw = 400 μsec and T0 = 1 msec, For example, power 100 W is supplied to the second feeding points 21 and 27, respectively, and two outputs of the second pulse modulation type phase variable two-output transmitter 28 of the constituent members of the second power supply system are provided. Is set to Δθ2 grasped as data of the second preliminary film-forming process, and the pulse modulation is performed with the pulse width Hw at W12 (t) and W22 (t) shown in FIGS. For example, the period T0 is Hw = 400 μsec and T0 = 1 msec, and set so as to rise at a time that is half a cycle, ie, T0 / 2 later than the pulse rise time of the pulse modulation of W11 (t) and W21 (t), For example, power of 100 W is supplied to the second feeding points 21 and 27, respectively. That is, the voltage waves W11 (x, t), W21 (x, t), W12 (x, t) and W22 (x, t) are supplied to the first and second feeding points 21 and 27. .
Here, the first pulse modulation type phase variable 2 output transmitter 15 and the second pulse modulation type phase variable 2 output transmitter set in the first preliminary film forming step and the second preliminary film forming step, respectively. For example, the values of 28 pulse widths Hw and period T0 can be changed from Hw = 400 μsec to 1 msec or the like, and T0 = 1 msec to 5 msec or the like.

When four voltage waves are supplied between the pair of electrodes 2 and 4, W11 (x, t) and W21 (x, t) interfere to form the first standing wave W1 (x, t). , W12 (x, t) and W22 (x, t) interfere to form a second standing wave W2 (x, t). However, W11 (x, t) does not interfere with W12 (x, t) and W22 (x, t) because they are temporally separated. Similarly, W21 (x, t) does not interfere with W12 (x, t) and W22 (x, t).
Accordingly, considering a general film formation time of several seconds or longer, which is significantly longer than the pulse modulation period T0, the distribution of the strength of power generated between the pair of electrodes 2 and 4 is the first standing wave. The intensity distribution I1 (x, t) of W1 (x, t) and the intensity distribution I2 (x, t) of the second standing wave W2 (x, t) are superimposed. This is conceptually shown in FIG.
Here, if the center point of the substrate is the origin of the x-axis and the direction from the origin toward the first feeding point 21 is a positive direction, the strength of the first standing wave W1 (x, t) Distribution I1 (x, t) is
I1 (x, t) ∝cos ² {2πx / 2 + 2π (λ / 8) / λ}
= Cos ² {2πx / 2 + π / 4}
The intensity distribution I2 (x, t) of the second standing wave W2 (x, t) is
I2 (x, t) ∝cos ² {2πx / 2-2π (λ / 8) / λ}
= Cos ² {2πx / 2−π / 4}
The distribution I (x, t) of the strength of power generated between the pair of electrodes 2 and 4 is
I (x, t)
= Cos ² {2πx / 2 + π / 4} + cos ² {2πx / 2−π / 4}
= 1

As a result, the high frequency used in the surface treatment apparatus for treating the surface of the substrate disposed in the vacuum vessel using the plasma generated using the power of the output of the high frequency power source whose oscillation frequency belongs to the VHF band or the UHF band. In the plasma generator, a first standing wave and a second standing wave are generated in which the positions of antinodes of the standing wave of the electromagnetic wave having an electric field substantially in the same direction as the normal direction of the surface of the substrate are different. In addition, the provision of means for superimposing the first and second standing waves makes it possible to control the distribution of power intensity between the electrodes, which is indispensable for plasma uniformity. .
Further, if the distance between the antinodes of the first and second standing waves is 0.25 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.25λ, a pair of electrodes The power intensity distribution I (x, t) generated between 2 and 4 has a constant value and does not depend on the position in the power propagation direction, and is uniform. This means that it is an epoch-making discovery in the sense that it is possible to provide a device capable of realizing large-area and uniform plasma processing, which is an important issue in the application field of VHF plasma or UHF plasma. Yes.
The distance between the antinodes of the first and second standing waves is 0.22 to 0.28 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.22 to 0.2. If it is 28λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 20% or less.
The distance between the antinodes of the first and second standing waves is 0.238 to 0.263 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.238 to. In the case of H.263λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 10% or less.

In the above process, when SiH 4 gas is turned into plasma, radicals such as SiH 3, SiH 2, and SiH existing in the plasma diffuse due to a diffusion phenomenon and are adsorbed on the surface of the substrate 11, thereby depositing an a-Si film. However, since the power distribution between the pair of electrodes 2 and 4 is uniform in time average as described above, the deposited film becomes uniform.
This indicates that the apparatus and method of the present invention can form a uniform film thickness distribution even when a substrate having a size exceeding one half of the wavelength λ is targeted. That is, even when a substrate having a size exceeding one-half of the wavelength λ, which is impossible with the conventional VHF plasma surface treatment apparatus and method, is targeted, the present invention can realize a uniform film thickness distribution. It means that.
Therefore, the above is an epoch-making discovery in the application field of VHF plasma, and its practical value is extremely large.
It is a well-known technique that microcrystalline Si, thin-film polycrystalline Si, or the like can be formed by optimizing the flow ratio, pressure, and power of SiH4 and H2 in the film forming conditions.
In addition, it is a known technique that can be applied to etching by using NF3, SF6, CF4, CHF3, C4F4, or the like as a discharge gas.

  In this embodiment, since the first electrode 2 is a single bar, the substrate size is limited to the above-mentioned 1200 mm × 100 mm. However, if the number of the rod electrodes as the first electrode 2 is increased, the width of the substrate size is increased. Of course, it is expandable.

Further, in the manufacture of a-Si solar cells, thin film transistors, and photosensitive drums, there is no problem in performance as long as the film thickness distribution is within ± 10%. According to the above embodiment, even when a power supply frequency of 60 MHz is used, the distribution of power intensity I (x, t) between the pair of electrodes 2 and 4 that is impossible with the conventional apparatus and method is uniform. Is possible. In other words, the film thickness distribution can be within ± 10%.
This means that a plasma surface treatment apparatus using a frequency in the VHF band or the UHF band as a means of drastic improvement in terms of productivity improvement and cost reduction in the manufacturing field of a-Si solar cells, thin film transistors, and photosensitive drums. Means that you can provide. The industrial value of this effect is significantly great.

Here, the pair of electrodes 2 and 4 having the structure shown in FIG. 2 which is one of the components of the apparatus of the present embodiment is replaced with the pair of electrodes 2 and 4 shown in FIG. It should be noted that the same plasma treatment as in this embodiment can be performed by using a plasma surface treatment apparatus instead of the pair of electrodes composed of 2 and the plate electrode 4.
In this case, as compared with the plasma generated by a pair of electrodes composed of the rod-shaped electrode 2 and the plate electrode 4 in FIG. 2, there is an advantage that it is possible to easily generate plasma having a spread in a direction perpendicular to the propagation direction of electromagnetic waves. is there.

Further, the pair of electrodes 2 and 4 having the structure shown in FIG. 2 which is one of the components of the apparatus of this embodiment is replaced with the pair of electrodes 2 and 4 having the structure shown in FIG. It should be noted that the same plasma treatment as in this embodiment can be performed by using a plasma surface treatment apparatus instead of the pair of electrodes composed of the electrode 2 and the plate electrode 4. Note that the line segment connecting the first power supply point 21a and the second power supply point 27a shown in FIG. 8 and the line segment connecting the third power supply point 21b and the fourth power supply point 27b need to be parallel. It is natural.
In this case, as compared with the plasma generated by the pair of electrodes composed of the rod-shaped electrode 2 and the plate electrode 4 shown in FIG. 2, it is possible to easily generate plasma that spreads in a direction perpendicular to the propagation direction of the electromagnetic wave. In addition to the above, there is an advantage that it is possible to distribute the power supplied to the feeding point. That is, it has a feature that it can be applied to plasma processing applications that require high power.

Further, a plasma surface treatment apparatus is used in which the pair of electrodes 2 and 4 having the structure shown in FIG. 2, which is one of the components of the apparatus of this embodiment, is replaced with the rod-like electrodes 2a and 2b having the structure shown in FIG. Note that the same plasma treatment as in this embodiment can be performed.
The first rod-like electrode 2a and the second rod-like electrode 2b shown in FIG. 9 need to be installed in parallel.
In this case, there is an advantage that it is possible to disperse the electric power supplied to the feeding point as compared with the plasma generated by the pair of electrodes composed of the rod-like electrode 2 and the plate electrode 4 shown in FIG. That is, it has a feature that it can be applied to plasma processing applications that require high power.
Further, in the above description, in the description of the generation of the standing wave of the electromagnetic wave using the high-frequency plasma generator according to the embodiment of the present invention and the plasma surface treatment apparatus constituted by the high-frequency plasma generator, the standing Although the number of waves is mainly described in the case of two, increasing the number to two or more can be easily performed by arranging a large number of feeding points.

(Example 3)
A high-frequency plasma generator according to a third embodiment of the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus will be described with reference to FIGS. explain. Reference is also made to FIG.
FIG. 13 is a schematic diagram showing an entire high-frequency plasma generator according to Example 3 and a plasma surface treatment apparatus (plasma CVD apparatus) constituted by the high-frequency plasma generator. 14 and 15 are wiring diagrams of the first and second power supply systems used in the apparatus shown in FIG.
FIG. 16 is an explanatory diagram showing a configuration relating to a pair of electrodes made of a rectangular conductor plate used in the apparatus shown in FIG.

First, the configuration of the apparatus will be described. However, the same members as those shown in the first and second embodiments are denoted by the same reference numerals, and the description thereof is omitted.
In FIG. 13 and FIG. 14, one output terminal of the two output terminals of the transmitter 15 having the first pulse modulation system variable phase output 2 is the first power amplifier 16, the first impedance matching unit 17, and the first output terminal. The second power distributor 71, one output terminal of the second power distributor 71, the current introduction terminal 18 a, and the core wire 20 a of the vacuum coaxial cable 19 a are connected via one output terminal of the power distributor 70. Is connected to the feeding point 21a via the other output terminal of the second power distributor 71, and is connected to the feeding point 21b via the current introduction terminal 18b and the core wire 20b of the vacuum coaxial cable 19b. In addition, the power is supplied via the other output terminal of the first power distributor 70 via one output terminal of the third power distributor 72, the current introduction terminal 18c, and the core wire 20c of the vacuum coaxial cable 19c. Is connected to a point 21c, it is connected the other output terminal of the third power divider 72, a current introduction terminal 18 d, to the feeding point 21d via the core wire 20d of the vacuum coaxial cable 19d.
As a typical example, the power supplied to the power supply points 21a to 21d is a sine wave that is pulse-modulated with a pulse width Hw and a period T0, as shown in W11 (t) in FIGS.
In addition, each of the branched coaxial cable lines has a structure, a material and a length so that the length of the propagation path of the power wave from the seventh power distributor 76 to the first feeding points 21a to 21d is the same. Are equal.

The other output terminal of the two output terminals of the transmitter 15 having the first pulse modulation system variable phase output 2 is one of the second power amplifier 22, the second impedance matcher 23, and the fourth power distributor 73. Is connected to the feeding point 27a via one output terminal of the fifth power distributor 74, the current introduction terminal 24a, and the core wire 26a of the vacuum coaxial cable 25a, and the fifth power The other output terminal of the distributor 74, the current introduction terminal 24b, and the core wire 26b of the vacuum coaxial cable 25b are connected to the feeding point 27b, and the other output terminal of the fourth power distributor 74 is connected. The sixth power distributor 75 is connected to the feeding point 27c via one output terminal of the sixth power distributor 75, the current introduction terminal 24c, and the core wire 26c of the vacuum coaxial cable 25c. An output terminal of the current introduction terminal 24d, is connected to a feeding point 27d via the core wire 26d of the vacuum coaxial cable 25d.
The power supplied to the feeding points 27a to 27b is typically pulse-modulated with the same pulse width Hw and period T0 as W11 (t) as shown in W21 (t) shown in FIGS. Sine wave.
In addition, each of the branched coaxial cable lines has a structure, a material and a length so that the length of the propagation path of the power wave from the seventh power distributor 76 to the first feeding points 21a to 21d is the same. Are equal.
Each of the first power amplifier 16 and the second power amplifier 22 is attached with a monitor for an output value (traveling wave) and a monitor for a reflected wave returning from the downstream side. In addition, an isolator for protecting the electric circuit of the first and second power amplifiers 16 and 22 by the reflected wave is attached.
Here, the power supply for supplying the two outputs of the first phase variable two-output transmitter 15 to the first and second feeding points 21a to 21d and 27a to 27d using the power amplifiers 16 and 22, respectively. The system is called a first power supply system.

In FIG. 13 and FIG. 15, one output terminal of the two output terminals of the second pulse modulation type phase-variable two-output transmitter 28 is a third power amplifier 29, a third impedance matcher 30, Through one output terminal of the seventh power distributor 76, the eighth power distributor 77, one output terminal of the eighth power distributor 77, the current introduction terminal 31 a, and the core wire of the vacuum coaxial cable 32 The power supply point 21a is connected to the power supply point 21a through the other output terminal of the eighth power distributor 77 and the power supply point 21b through the core wire 33b of the vacuum coaxial cable 32b. Through the other output terminal of the seventh power distributor 76, one output terminal of the ninth power distributor 78, the current introduction terminal 31c, and the core wire 33c of the vacuum coaxial cable 32c are connected. Is connected to the feeding point 21c Te, is connected the other output terminal of the power distributor 78 of said 9, cable terminal 31d, the feeding point 21d via the core wire 33d of the vacuum coaxial cable 32d.
Note that, as a typical example, the power supplied to the feeding points 21a to 21d has a pulse width Hw, a period T0, and the W11 (t) and W21 ( This is a pulse-modulated sine wave that rises at a time that is half a period, ie, T0 / 2 later than the pulse rise time of the pulse modulation of t).
In addition, each of the branched coaxial cable lines has a structure, a material and a length so that the length of the propagation path of the power wave from the seventh power distributor 76 to the first feeding points 21a to 21d is the same. Are equal.
The other output terminal of the two output terminals of the transmitter 28 of the second pulse modulation type phase variable two output is one of the fourth power amplifier 34, the fourth impedance matching unit 35, and the tenth power distributor 79. To the feeding point 27a via the eleventh power distributor 80, one output terminal of the eleventh power distributor 80, the current introduction terminal 36a, the vacuum coaxial cable 37a and the connection line 38a. And connected to the feeding point 27b via the other output terminal of the eleventh power distributor 80, the current introduction terminal 36b, the vacuum coaxial cable 37b and the connection line 38b, and the tenth power. Via the other output terminal of the distributor 79, the feed point 27c via one output terminal of the twelfth power distributor 81, the current introduction terminal 36c, the vacuum coaxial cable 37c, and the connection line 38c. Is connected, it is connected the other output terminal of the power distributor 81 of the said 12, the current introduction terminal 36d, the feeding point 27d via the coaxial cable 37d and the connecting wire 38d vacuum.
Note that, as a typical example, the power supplied to the feeding points 27a to 27b has a pulse width Hw, a period T0, and the W11 (t) and W21 ( This is a pulse-modulated sine wave that rises at a time that is half a period, ie, T0 / 2 later than the pulse rise time of the pulse modulation of t).
Further, each of the branched coaxial cable lines has a structure, a material, and a length so that the length of the propagation path of the power wave from the tenth power distributor 79 to the second feeding points 27a to 27d is the same. Are equal.
The third power amplifier 29 and the fourth power amplifier 34 are each accompanied by a monitor for output value (traveling wave) and a monitor for reflected wave that returns from the downstream side. Further, an isolator for protecting the electric circuit of the third and fourth power amplifiers 29 and 34 by the reflected wave is attached.
Here, the power supply for supplying the two outputs of the second phase variable and two-output transmitter 28 to the first and second feeding points 21a to 21d and 27a to 27d using the power amplifiers 29 and 34, respectively. The system is called a second power supply system.

  Next, a method for manufacturing an amorphous Si film for an a-Si solar cell using the plasma surface treatment apparatus having the above configuration will be described. In the implementation or application of the present invention, the first and second preliminary film forming steps and the main film forming step are necessary as procedures. The first preliminary film forming step includes the step of determining the phase difference between the two outputs of the first pulse modulation type phase-variable two-output transmitter 15. In order to grasp the set value of the phase difference between the two outputs of the transmitter 28 having the second pulse modulation type variable phase two output, this film forming process is carried out for the purpose of manufacturing the target amorphous Si.

First, in the first preliminary film forming step, in FIGS. 13 and 14, a substrate 11 (not shown) is previously set on the second electrode 4, a vacuum pump 10 (not shown) is operated, and the vacuum container 1 is operated. After removing the impurity gas in the substrate, the substrate temperature is in the range of 80 to 350 ° C. while supplying SiH 4 gas from a discharge gas supply tube 8 (not shown) at 500 sccm and a pressure of 0.5 Torr (66.5 Pa), for example, Hold at 180 ° C.
Then, using the first power supply system, high-frequency power is supplied to the first and second feeding points 21a to 21d and 27a to 27d, for example, power having a frequency of 60 MHz, for example, 500 W in total.
That is, the phase difference between the two outputs of the first pulse modulation type phase-variable two-output transmitter 15 is set to, for example, zero, the pulse width Hw = 400 μsec, and the period T0 = 1 msec. The outputs of the amplifier 16 and the second power amplifier 22 are respectively set to 250 W at a frequency of 60 MHz and supplied to both ends of the first electrode.
Here, typical examples of power supplied to the first and second feeding points 21a to 21d and 27a to 27d are shown as W11 (t) and W21 (t) in FIGS. The W11 (t) and W21 (t) are sine waves having a pulse width Hw and a pulse modulation with a period T0, for example, 60 MHz. The pulse width Hw and period T0 are set to arbitrary values, for example, Hw = 400 μsec and period T0 = 1 msec, by a regulator attached to the first pulse modulation system phase variable 2-output transmitter 15.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above-described manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 15 having the first phase variable and two outputs as a parameter. Then, in the length direction of the first electrodes 2a to 2d, the distance from the center point of the substrate 11 to the position of the maximum thickness of the sinusoidal film thickness distribution and 2 of the transmitter 15 of the first phase variable 2 output. The relationship between the phase differences of the two outputs is grasped as data. For example, the phase difference for setting a position that is one-eighth of the wavelength λ, that is, λ / 8 away from the center point of the substrate 11 in the direction of the first feeding points 21a to 21d is, for example, Δθ1. Is grasped.
Note that the method of grasping the relationship between the maximum position of the sinusoidal thickness distribution and the phase difference of the output voltage of the first variable-phase two-output transmitter 15a performed here is the measurement of the thickness distribution of the film. The method is not limited to the application method. For example, the spatial distribution of the emission intensity of the generated plasma in the electromagnetic wave propagation direction is measured with an optical sensor, and the relationship between the position of the maximum intensity and the phase difference is grasped. Also good.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Next, in the second preliminary film-forming step, in FIGS. 13 and 15, a substrate 11 (not shown) is previously placed on the second electrode 4 and a vacuum pump 10 (not shown) is operated to operate a vacuum container. After removing the impurity gas and the like in 1, the substrate temperature is in the range of 80 to 350 ° C. while supplying SiH 4 gas from a discharge gas supply tube 8 (not shown) at 500 sccm and a pressure of 0.5 Torr (66.5 Pa), for example. For example, it is maintained at 180 ° C.
Then, using the second power supply system, high-frequency power is supplied to the first and second feeding points 21a to 21d and 27a to 27d, for example, power having a frequency of 60 MHz, for example, 500 W in total.
That is, the phase difference between the two outputs of the second pulse modulation type phase-variable two-output transmitter 28 is set to, for example, zero, the pulse width Hw = 400 μsec, and the pulse period T0 = 1 msec. The outputs of the power amplifier 29 and the second power amplifier 34 are set to 250 W at a frequency of 60 MHz, respectively, and supplied to both ends of the first electrode.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above-described manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 28 having the first phase variable and two outputs as a parameter. Then, in the length direction of the first electrode, the distance from the center point of the substrate 11 to the position of the maximum thickness of the sinusoidal film thickness distribution and 2 of the transmitter 28 of the second pulse modulation type phase variable 2 output. The relationship between the phase differences of the two outputs is grasped as data. For example, it is understood that the phase difference for setting a position that is one-eighth of the wavelength λ from the center point of the substrate 11 toward the second feeding point 27, that is, a position separated by λ / 8 is, for example, Δθ2. Is done.
Note that the method of grasping the relationship between the maximum position of the sinusoidal thickness distribution and the phase difference of the output voltage of the first variable-phase two-output transmitter 15a performed here is the measurement of the thickness distribution of the film. The method is not limited to the application method. For example, the spatial distribution of the emission intensity of the generated plasma in the electromagnetic wave propagation direction is measured with an optical sensor, and the relationship between the position of the maximum intensity and the phase difference is grasped. Also good.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Now, in response to the results of the first and second preliminary film forming steps, the main film forming step is started. First, in FIG. 13 to FIG. 15, the substrate 11 is set on the second electrode 4 in advance, the vacuum pump 10 (not shown) is operated, the impurity gas in the vacuum vessel 1 is removed, and the discharge gas is supplied. While supplying SiH 4 gas from the tube 8 at 800 sccm and a pressure of 0.5 Torr (66.5 Pa), the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C.
Next, the phase difference between the two outputs of the first pulse modulation type phase variable 2-output transmitter 15 of the component of the first power supply system, for example, the voltage of a sine wave power having a frequency of 60 MHz Δθ1 obtained from the preliminary test data is set, and the pulse modulation of the pulse width Hw and period T0 in W11 (t) and W21 (t) shown in FIGS. 11 and 12 is set to, for example, Hw = 400 μsec and T0 = 1 msec. For example, 500 W is supplied to the first and second feeding points 21a to 21b and 27a to 27b, respectively, and the second pulse modulation scheme phase variable of the constituent members of the second power supply system is set. A phase difference between two outputs of the two-output transmitter 28, for example, a sine wave power having a frequency of 60 MHz, is set to Δθ2 obtained from the second preliminary test data, and the pulse modulation is shown in FIGS. The pulse width Hw and period T0 in W12 (t) and W22 (t) are, for example, Hw = 400 μsec and T0 = 1 msec, and from the pulse rise time of the pulse modulation of W11 (t) and W21 (t) It is set to rise at a half cycle, that is, at a time delayed by T0 / 2, and for example, power 500 W is supplied to the first and second feeding points 21a to 21b and 27a to 27b, respectively.
That is, a voltage wave W11 (x, t) with a power of 250 W, a voltage wave W21 (x, t) with a power of 250 W, and a W12 with power of 250 W are applied to the first and second feeding points 21a to 21b and 27a to 27b, respectively. (X, t) and W22 (x, t) with a power of 250 W are supplied.
Here, the first pulse modulation type phase variable 2 output transmitter 15 and the second pulse modulation type phase variable 2 output transmitter set in the first preliminary film forming step and the second preliminary film forming step, respectively. For example, the values of 28 pulse widths Hw and period T0 can be changed from Hw = 400 μsec to 1 msec or the like, and T0 = 1 msec to 5 msec or the like.

When power consisting of four voltage waves is supplied between the pair of electrodes 2a to 2d and 4 via the first and second feeding points 21a to 21b and 27a to 27b, as described above, W11 (X, t) and W21 (x, t) interfere to form a first standing wave W1 (x, t), and W12 (x, t) and W22 (x, t) interfere with each other. 2 standing waves W2 (x, t) are formed. However, W11 (x, t) does not interfere with W12 (x, t) and W22 (x, t) because they are temporally separated. Similarly, W21 (x, t) does not interfere with W12 (x, t) and W22 (x, t).
Therefore, considering a general film formation time of several seconds or longer, which is significantly longer than the pulse modulation period T0, the distribution of the strength of power generated between the pair of electrodes 2a to 2d and 4 is the first constant. The intensity distribution I1 (x, t) of the standing wave W1 (x, t) and the intensity distribution I2 (x, t) of the second standing wave W2 (x, t) are superimposed. This is conceptually shown in FIG.
Here, assuming that the center point of the substrate is the origin of the x axis and the direction from the origin toward the first feeding points 21a to 21d is a positive direction, the strength of the first standing wave W1 (x, t) is strong. The distribution of thickness I1 (x, t) is
I1 (x, t) = cos ² {2πx / 2 + 2π (λ / 8) / λ}
= Cos ² {2πx / 2 + π / 4}
The intensity distribution I2 (x, t) of the second standing wave W2 (x, t) is
I2 (x, t) = cos ² {2πx / 2-2π (λ / 8) / λ}
= Cos ² {2πx / 2−π / 4}
The distribution I (x, t) of the strength of power generated between the pair of electrodes 2a to 2d, 4 is
I (x, t)
= Cos ² {2πx / 2 + π / 4} + cos ² {2πx / 2−π / 4}
= 1

As a result, the high frequency used in the surface processing apparatus for processing the surface of the substrate disposed in the vacuum vessel using the plasma generated using the power of the output of the high frequency power source whose oscillation frequency belongs to the VHF band or the UHF band. In the plasma generator, the first standing wave and the second standing wave are generated in different positions of antinodes of the standing wave of the electromagnetic wave having an electric field substantially in the same direction as the normal direction of the surface of the substrate. And, by providing means for superimposing the first and second standing waves, it means that it is possible to control the distribution of power intensity between the electrodes, which is indispensable for plasma uniformity. ing.
Further, if the distance between the antinodes of the first and second standing waves is 0.25 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.25λ, a pair of electrodes The power intensity distribution I (x, t) generated between 2 and 4 has a constant value and does not depend on the position in the power propagation direction, and is uniform. This means that it is an epoch-making discovery in the sense that it is possible to provide an apparatus capable of realizing large-area and uniform plasma processing, which is an important issue in the application field of UHF plasma and UHF plasma. Yes.
The distance between the antinodes of the first and second standing waves is 0.22 to 0.28 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.22 to 0.2. If it is 28λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 20% or less.
The distance between the antinodes of the first and second standing waves is 0.238 to 0.263 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.238 to. In the case of H.263λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 10% or less.

In the above process, when SiH 4 gas is turned into plasma, radicals such as SiH 3, SiH 2, and SiH existing in the plasma diffuse due to a diffusion phenomenon and are adsorbed on the surface of the substrate 11, thereby depositing an a-Si film. However, since the power distribution between the pair of electrodes 2 and 4 is uniform on a time average as described above, the deposited film becomes uniform.
This indicates that according to the present invention, a uniform film thickness distribution can be formed even when a substrate having a size exceeding one-half of the wavelength λ is targeted. That is, even when a substrate having a size exceeding one-half of the wavelength λ, which is impossible with the conventional VHF plasma surface treatment apparatus and method, is targeted, the present invention can realize a uniform film thickness distribution. It means that.
Therefore, the above is an epoch-making discovery in the application field of VHF plasma, and its practical value is extremely large.

It is a well-known technique that microcrystalline Si, thin-film polycrystalline Si, or the like can be formed by optimizing the flow ratio, pressure, and power of SiH4 and H2 in the film forming conditions.
In addition, it is a known technique that can be applied to etching by using NF3, SF6, CF4, CHF3, C4F4, or the like as a discharge gas.

In this embodiment, the size of the rod electrode used for the first electrode is about 5 to 20 mm in diameter, the interval is about 5 to 30 mm, the length is about 1400 mm to 1800 mm, and the first rod electrode and the second flat plate are used. By setting the distance of the electrode (ground electrode) to about 5 to 40 mm, the amorphous Si film can be formed at a film forming speed of about 1 to 3 nm / s and a film thickness distribution within ± 10%.
Naturally, application to a wide substrate can be dealt with by increasing the number of rod electrodes and the number of power supply systems. That is, it is possible to cope with the problem by arranging a large number of rod electrodes and a power supply system to generate a large number of standing waves and superimposing them. Further, by providing the above-described means for controlling the position of the antinode of the standing wave, it is possible to reliably realize the uniform plasma.

In this embodiment, the plurality of rod electrodes and the plate electrodes shown in FIGS. 13 to 15 are used as the pair of electrodes for generating the plasma. However, the plurality of rod electrodes are replaced with, for example, the plate electrodes shown in FIG. Of course, it is possible to use different configurations. In this case, it is preferable to use a flat plate having a gas passage hole 13 as one of the pair of electrodes as shown in FIG.
Moreover, it is natural that the structure of the electrode or the power feeding part in FIGS. 13 to 16 can be replaced with the electrode or power feeding part structure shown in FIGS.

Example 4
A high-frequency plasma generation apparatus according to Embodiment 4 of the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus will be described with reference to FIGS. explain. Reference is also made to FIGS.
FIG. 17 is a schematic view showing an entire high-frequency plasma generator according to the fourth embodiment and a plasma surface treatment apparatus (plasma CVD apparatus) constituted by the high-frequency plasma generator, and FIG. 18 is a vacuum of the plasma surface treatment apparatus shown in FIG. It is sectional drawing inside a container.
FIG. 19 is an explanatory view showing a first applied type of a configuration related to a pair of electrodes used as a component of the apparatus shown in FIG. 17 and its power feeding portion, and FIG. 20 is a component of the apparatus shown in FIG. FIG. 21 is a diagram illustrating a second applied type of the configuration related to the pair of electrodes used as a power supply unit and the power supply unit, and FIG. 21 illustrates the configuration related to the pair of electrodes used as a component of the apparatus illustrated in FIG. It is explanatory drawing which shows the 3rd applied type.

First, the configuration of the apparatus will be described. However, the same members as those shown in the first to third embodiments are denoted by the same reference numerals, and description thereof is omitted.
In FIG. 17 and FIG. 18, reference numeral 109 denotes a substrate support material that incorporates a substrate heater 3 (not shown). The first and second electrodes 2 and 4 are rectangular flat plate-shaped holes having a diameter of about 3 mm and are set at an aperture ratio of about 55%. The thickness is about 6 mm and the area is about 1500 mm × 300 mm. The feeding point 21 is installed at the center of one side of the rectangular plate electrode, and the feeding point 27 is installed at the center of the opposite side. The distance between the electrodes 2 and 4 can be arbitrarily set to about 5 to 50 mm. As the substrate 11, a glass substrate having a thickness of about 2 to 4 mm and an area of about 1400 mm × 200 mm is used. The discharge gas is supplied from the discharge gas supply pipe 8 through the rectifying hole 7 of the gas mixing box 6.

  Next, a method of manufacturing an amorphous Si film for an a-Si solar cell using the high-frequency plasma generator having the above-described configuration and a plasma surface treatment apparatus including the high-frequency plasma generator will be described. In the implementation or application of the present invention, the first and second preliminary film forming steps and the main film forming step are necessary as procedures. In the first preliminary film-forming process, in order to grasp the set value of the phase difference between the two outputs of the first pulse modulation type phase-variable two-output transmitter 15, In order to ascertain the set value of the phase difference between the two outputs of the two pulse modulation type phase-variable two-output transmitter 28, this film-forming step is performed for the production of the target amorphous Si.

First, in the first first preliminary film forming step, in FIGS. 17 and 18, the substrate 11 is previously set on the substrate support material 109, the vacuum pump 10 (not shown) is operated, and the vacuum container 1 is operated. After removing the impurity gas and the like in the substrate, the substrate temperature is in the range of 80 to 350 ° C., for example, 180 ° C. while supplying SiH 4 gas from the discharge gas supply tube 8 at 500 sccm and the pressure of 0.5 Torr (66.5 Pa), for example. Hold on.
Next, the first pulse modulation type phase-variable two-output transmitter 15, the first power amplifier 16, the first impedance matching unit 17, the first current introduction terminal 18, and the first vacuum coaxial cable 19. A first power supply system comprising a core wire 20, a second power amplifier 22, a second impedance matching device 23, a second current introduction terminal 24, and a core wire 26 of a second vacuum coaxial cable 25, The pair of electrodes 2 and 4 is supplied with high frequency power, for example, power with a frequency of 60 MHz, for example, 400 W in total.
That is, the phase difference between the two outputs of the first pulse modulation system phase variable 2-output transmitter 15 is set to, for example, zero, pulse modulation pulse width Hw = 400 μsec, and pulse period T0 = 1 msec. The output of the first power amplifier 16 is set to 200 W, and the output is passed through the first impedance matching unit 17, the first current introduction terminal 18, and the core wire 20 of the first vacuum coaxial cable 19. 1 is supplied to one feeding point 21, the output of the second power amplifier 22 is set to 200 W, and the output is supplied to the second impedance matching unit 23, the second current introduction terminal 24, and the second vacuum coaxial. This is supplied to the second feeding point 27 via the core wire 26 of the cable 25.
In this case, by adjusting the first impedance matching unit 17 and the second impedance matching unit 23, it is possible to prevent the reflected wave of the supplied power from returning to the upstream side of the respective impedance matching units 17 and 23.
Here, typical examples of power supplied to the first and second feeding points 21 and 27 are shown as W11 (t) and W21 (t) in FIGS. 11 and 12, respectively. W11 (t) and W21 (t) are sine waves of ultrahigh frequency, for example, 60 MHz, pulse-modulated with a pulse width Hw = 400 μsec and a period T0 = 1 msec, respectively. The pulse width Tw and the period T0 are set to arbitrary values, for example, Tw = 400 μsec and the period T0 = 1 msec by an adjuster attached to the transmitter 15 having the first pulse modulation system variable phase 2 output.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 15 having the first pulse modulation type variable phase two output as a parameter.
In the direction of the line segment connecting the feeding points 21 and 27, the distance from the center point of the substrate 11 to the position of the maximum thickness of the sinusoidal film thickness distribution and the first pulse modulation type phase variable two-output transmitter The relationship between the phase differences between the two 15 outputs is grasped as data. For example, it is understood that the phase difference for setting a position that is one-eighth of the wavelength λ from the center point of the substrate 11 toward the first feeding point 21, that is, a position that is separated by λ / 8 is Δθ1, for example. Is done.
Note that the method of grasping the relationship between the maximum position of the sinusoidal thickness distribution and the phase difference of the output voltage of the first variable-phase two-output transmitter 15a performed here is the measurement of the thickness distribution of the film. The method is not limited to the application method. For example, the spatial distribution of the emission intensity of the generated plasma in the electromagnetic wave propagation direction is measured with an optical sensor, and the relationship between the position of the maximum intensity and the phase difference is grasped. Also good.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Next, in the second preliminary film forming step, in FIGS. 17 and 18, the substrate 11 is previously set on the substrate support material 109, the vacuum pump 10 (not shown) is operated, After removing the impurity gas and the like, the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C. while supplying SiH 4 gas from the discharge gas supply tube 8 at 500 sccm and a pressure of 0.5 Torr (66.5 Pa), for example. To do.
The second pulse modulation type phase-variable two-output transmitter 28, the third power amplifier 29, the third impedance matching unit 30, the third current introduction terminal 31, and the third coaxial coaxial cable 32 are provided. Using a second power supply system comprising a core wire 33, a fourth power amplifier 34, a fourth impedance matching device 35, a fourth current introduction terminal 36, and a core wire 38 of a fourth vacuum coaxial cable 37, a pair The electrodes 2 and 4 are supplied with high-frequency power, for example, power with a frequency of 60 MHz, for example, 400 W in total.
That is, the phase difference between the two outputs of the second pulse modulation method phase-variable two-output transmitter 28 is set to, for example, zero, the pulse width of the pulse modulation = 400 μsec, and the pulse period = 1 ms, The output of the power amplifier 29 is set to 200 W, and the output is supplied to the first impedance matcher 30, the third current introduction terminal 31, and the core wire 33 of the third vacuum coaxial cable 32 through the first impedance matching unit 30. The power is supplied to the feeding point, the output of the fourth power amplifier 34 is set to 200 W, and the output of the fourth impedance matching unit 35, the fourth current introduction terminal 36, and the fourth vacuum coaxial cable 37 is set. It is supplied to the second feeding point via the core wire 38.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 has a sinusoidal distribution due to the generation of a standing wave that is a phenomenon inherent to the VHF plasma. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 28 of the second pulse modulation type variable phase output 2 as a parameter. Then, in the length direction of the first electrode, the distance from the center point of the substrate to the position of the maximum thickness of the sinusoidal film thickness distribution and the two transmitters 28 of the second pulse modulation type phase variable two output Grasp the relationship of output phase difference as data.
Also in this case, similarly to the first preliminary film forming step, in the case where the second power supply system is used, the distance from the center point of the substrate to the position of the maximum thickness of the sinusoidal film thickness distribution and the first The position of the maximum thickness of the film thickness distribution, for example, from the center point of the substrate to the second feeding point 27 is obtained from data indicating the relationship between the two output phase differences of the two pulse modulation type phase-variable two-output transmitters 28. It can be seen that the phase difference for setting the position to one-eighth of the wavelength λ in the direction, that is, the position separated by λ / 8 is, for example, Δθ2.
Note that the method of grasping the relationship between the maximum position of the sinusoidal thickness distribution and the phase difference of the output voltage of the first variable-phase two-output transmitter 15a performed here is the measurement of the thickness distribution of the film. The method is not limited to the application method. For example, the spatial distribution of the emission intensity of the generated plasma in the electromagnetic wave propagation direction is measured with an optical sensor, and the relationship between the position of the maximum intensity and the phase difference is grasped. Also good.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Now, in response to the results of the first and second preliminary film forming steps, the main film forming step is started. First, in FIG. 17 and FIG. 18, the substrate 11 is previously set on the substrate support material 109, the vacuum pump 10 (not shown) is operated to remove the impurity gas and the like in the vacuum vessel 1, and then the discharge gas supply pipe The substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C. while supplying SiH 4 gas from 8 at 500 sccm and a pressure of 0.5 Torr (66.5 Pa).
Next, two preliminary outputs of the first pulse modulation type phase-variable two-output transmitter 15 of the constituent members of the first power supply system, for example, a phase difference of a sine wave with a frequency of 60 MHz are used as a first preliminary film forming step. Is set to Δθ1 grasped as the data of, and the pulse modulation is set to the pulse width Hw and the period T0 in W11 (t) and W21 (t) shown in FIGS. 11 and 12, for example, Hw = 400 μsec and T0 = 1 ms The first and second feeding points 21 and 27 are each supplied with, for example, electric power of 200 W, and the second pulse modulation type phase-variable two-output transmitter of the constituent member of the second electric power supply system. The phase difference between the two outputs of 28 is set to Δθ2 grasped as the data of the second preliminary film forming step, and the pulse modulation is performed with the pulse width Hw at W12 (t) and W22 (t) shown in FIGS. And around The period T0 is set to rise at, for example, Hw = 400 μsec and T0 = 1 msec, and a half cycle, ie, a time delayed by T0 / 2 from the pulse rise time of the pulse modulation of W11 (t) and W21 (t). Then, for example, electric power of 200 W is supplied to the first and second feeding points 21 and 27, respectively.
That is, at the first and second feeding points 21 and 27, a voltage wave W11 (x, t) with a power of 200 W, a voltage wave W12 (x, t) with a power of 200 W, and a W21 (x, t) with a power of 200 W, respectively. ) And W22 (x, t) with power of 200 W are supplied.
Here, the first pulse modulation type phase variable 2 output transmitter 15 and the second pulse modulation type phase variable 2 output transmitter set in the first preliminary film forming step and the second preliminary film forming step, respectively. For example, the values of 28 pulse widths Hw and period T0 can be changed from Tw = 400 μsec to 1 msec or the like, and T0 = 1 msec to 5 msec or the like.

When four voltage waves are supplied between the pair of electrodes 2, 4, as described above, W 11 (x, t) and W 21 (x, t) interfere with each other and the first standing wave W 1 (x, t t), and W12 (x, t) and W22 (x, t) interfere to form a second standing wave W2 (x, t). However, W11 (x, t) does not interfere with W12 (x, t) and W22 (x, t) because they are temporally separated. Similarly, W21 (x, t) does not interfere with W12 (x, t) and W22 (x, t).
Accordingly, considering a general film formation time of several seconds or longer, which is significantly longer than the pulse modulation period T0, the distribution of the strength of power generated between the pair of electrodes 2 and 4 is the first standing wave. The intensity distribution I1 (x, t) of W1 (x, t) and the intensity distribution I2 (x, t) of the second standing wave W2 (x, t) are superimposed. This is conceptually shown in FIG.
Here, if the center point of the substrate is the origin of the x-axis and the direction from the origin toward the first feeding point 21 is a positive direction, the strength of the first standing wave W1 (x, t) Distribution I1 (x, t) is
I1 (x, t) ∝cos ² {2πx / 2 + 2π (λ / 8) / λ}
= Cos ² {2πx / 2 + π / 4}
The intensity distribution I2 (x, t) of the second standing wave W2 (x, t) is
I2 (x, t) ∝cos ² {2πx / 2-2π (λ / 8) / λ}
= Cos ² {2πx / 2−π / 4}
The distribution I (x, t) of the strength of power generated between the pair of electrodes 2 and 4 is
I (x, t)
= Cos ² {2πx / 2 + π / 4} + cos ² {2πx / 2−π / 4}
= 1

As a result, the high frequency used in the surface processing apparatus for processing the surface of the substrate disposed in the vacuum vessel using the plasma generated using the power of the output of the high frequency power source whose oscillation frequency belongs to the VHF band or the UHF band. In the plasma generator, the first standing wave and the second standing wave are generated in different positions of antinodes of the standing wave of the electromagnetic wave having an electric field substantially in the same direction as the normal direction of the surface of the substrate. And, by providing means for superimposing the first and second standing waves, it means that it is possible to control the distribution of power intensity between the electrodes, which is indispensable for plasma uniformity. ing.
Further, if the distance between the antinodes of the first and second standing waves is 0.25 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.25λ, a pair of electrodes The power intensity distribution I (x, t) generated between 2 and 4 has a constant value and does not depend on the position in the power propagation direction, and is uniform. This means that it is an epoch-making discovery in the sense that it is possible to provide an apparatus capable of realizing large-area and uniform plasma processing, which is an important issue in the application field of UHF plasma and UHF plasma. Yes.
The distance between the antinodes of the first and second standing waves is 0.22 to 0.28 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.22 to 0.2. If it is 28λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 20% or less.
The distance between the antinodes of the first and second standing waves is 0.238 to 0.263 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.238 to. In the case of H.263λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 10% or less.

In the above process, when SiH 4 gas is turned into plasma, radicals such as SiH 3, SiH 2, and SiH existing in the plasma are diffused through the opening of the first electrode 2 and adsorbed on the surface of the substrate 11. As a result, the power distribution between the pair of electrodes 2 and 4 is uniform on a time average basis as described above, so that the deposited film is uniform.
This indicates that according to the present invention, a uniform film thickness distribution can be formed even when a substrate having a size exceeding one-half of the wavelength λ is targeted. That is, even when a substrate having a size exceeding one-half of the wavelength λ, which is impossible with the conventional VHF plasma surface treatment apparatus and method, is targeted, the present invention can realize a uniform film thickness distribution. It means that.
Therefore, the above is an epoch-making discovery in the application field of VHF plasma, and its practical value is extremely large.
It is a well-known technique that microcrystalline Si, thin-film polycrystalline Si, or the like can be formed by optimizing the flow ratio, pressure, and power of SiH4 and H2 in the film forming conditions.
In addition, it is a known technique that can be applied to etching by using NF3, SF6, CF4, CHF3, C4F4, or the like as a discharge gas.

In this embodiment, since the feeding point of the first electrode 2 is one point at the center of the opposite side, the substrate size is limited to about 1400 mm × 200 mm, but the width of the electrode is increased and the feeding point is increased. Of course, by increasing the number of points, the width of the substrate size can be expanded. However, in this case, the interval between adjacent feeding points is preferably about 100 mm to 300 mm.
If the substrate has a large area, it can be handled by increasing the width of the pair of electrodes 2 and 4 of the constituent members of the plasma surface treatment apparatus shown in FIG. That is. That is, this can be dealt with by using a configuration in which a plurality of feeding points are arranged as in the plasma surface treatment apparatus shown in FIGS. 13 to 15 and 16 shown as the third embodiment.

  Further, in the manufacture of a-Si solar cells, thin film transistors, and photosensitive drums, there is no problem in performance as long as the film thickness distribution is within ± 10%. According to the above embodiment, even if a power supply frequency of 60 MHz is used, it is possible to obtain a film thickness distribution that is significantly better than the conventional apparatus and method, for example, within ± 10%. This means that the industrial value related to productivity improvement and cost reduction in the manufacturing field of a-Si solar cells, thin film transistors, and photosensitive drums is remarkably large.

Here, as an application when changing the positions of the feeding points 21 and 27, components of the high-frequency plasma generator shown in FIGS. 17 and 18 and a plasma surface treatment apparatus (plasma CVD apparatus) constituted by the high-frequency plasma generator. FIG. 19 shows an example of a configuration in which the position of the feeding point is arranged at the corner of the rectangular electrode. In this case, since the spreading angle of the four electromagnetic waves forming the first and second standing waves in the vicinity of the feeding point is narrower than in the case of the apparatus shown in FIGS. It can be expected that the wave control becomes easier.
Further, as an application to the case where the substrate shape is circular, it is one of the constituent members of the high-frequency plasma generator shown in FIGS. 17 and 18 and a plasma surface treatment apparatus (plasma CVD apparatus) constituted by the high-frequency plasma generator. 21 shows an example of a device in which the structure of the pair of electrodes is replaced with a structure composed of a spiral electrode 2 and a disk electrode 4 shown in FIG. In this case, a merit that plasma suitable for surface treatment of a circular substrate can be generated can be expected.

In addition, as an application to means for further increasing the plasma density, an example of a high-frequency plasma generator capable of generating standing waves whose propagation directions are orthogonal to each other by arranging feeding points on the four sides of the rectangular electrode Is shown in FIG. In the apparatus shown in FIG. 21, in the case of application to a large-area substrate, the number of feeding points arranged on the four sides of the electrode is increased, and a large number of standing waves propagating in directions orthogonal to each other are generated. This is possible.
The constituent members of the apparatus shown in FIG. 21 are the same as those in the above embodiment, and the description thereof is omitted.
In general, the plasma density increases in proportion to the amount of power supplied, but the coaxial cable used for power supply at a frequency in the VHF band or the UHF band has a large power loss and has certain limitations. Therefore, it is difficult to transmit power that exceeds the constraint value. Therefore, it is impossible to further increase the plasma density.
In the apparatus configuration shown in FIG. 21, it is possible to supply power necessary for generating two required standing waves from directions in which propagation directions are orthogonal to each other. That is, it is possible to supply twice as much power as in the case of the device configuration with the above restrictions. As a result, it is possible to obtain about twice the plasma density.

(Example 5)
A plasma generator of Example 5 relating to the present invention, and a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the plasma generator will be described with reference to FIGS. .
FIG. 22 is a schematic diagram showing an entire plasma generator according to the fifth embodiment and a plasma surface treatment apparatus (plasma CVD apparatus) constituted by the plasma generator, and FIG. 23 is a power supply system of the plasma surface treatment apparatus shown in FIG. It is explanatory drawing which shows a wiring diagram.

First, the configuration of the apparatus will be described. However, the same members as those shown in the first to fourth embodiments are denoted by the same reference numerals, and description thereof is omitted.
22 and 23, the first electrode 2 uses a U-shaped electrode made of a SUS rod having a diameter of about 5 to 20 mm. The length of the U-shaped straight portion is about 1400 mm, and the distance between the straight bars is about 10 to 40 mm. The distance between the U-shaped electrode and the second plate electrode can be arbitrarily set to about 5 to 50 mm. As the substrate 11, a glass substrate having a glass substrate area of about 1200 mm × 200 mm having a thickness of about 4 mm is used.
Preferably, the total length of the U-shaped bar is a half of the wavelength λ of the power used, that is, an integral multiple of λ / 2. Further, the bent portion of the U-shaped electrode is covered with a dielectric such as alumina.

22 and 23, one output terminal of the two output terminals of the first pulse modulation type phase-variable two-output transmitter 15 is the first power amplifier 16, the first impedance matching unit 17, the first output terminal. The current introduction terminal 18 and the core wire 20 at the end of the first vacuum coaxial cable 19 are connected to the first feeding point 21. The outer conductor at the end of the first vacuum coaxial cable 19 is connected to the second electrode 4.
The other output terminal of the two output terminals of the first pulse modulation type phase-variable two-output transmitter 15 is the second power amplifier 22, the second impedance matching unit 23, the second current introduction terminal 24, and the second output terminal. 2 is connected to a second feeding point 27 via a core wire 26 at the end of the vacuum coaxial cable 25. The outer conductor at the end of the second vacuum coaxial cable 19 is connected to the second electrode 4.
Each of the first power amplifier 16 and the second power amplifier 22 is attached with a monitor for an output value (traveling wave) and a monitor for a reflected wave returning from the downstream side. In addition, an isolator for protecting the electric circuit of the first and second power amplifiers 16 and 22 by the reflected wave is attached.
Here, a power supply system for supplying the two outputs of the first pulse modulation type phase-variable two-output transmitter 15 to the first and second feeding points 21 and 27 by the power amplifiers 16 and 22 respectively. This is called a first power supply system.

22 and FIG. 23, the second pulse modulation system variable phase 2 output transmitter 28 is the pulse modulation of the first pulse modulation system variable phase 2 output transmitter 15 transmitted via the synchronization signal cable 100. Using the waveform synchronization signal, the power of the pulse modulation synchronized with the pulse modulation waveform of the output of the transmitter 15 having the first pulse modulation system variable phase 2 output is output.
One of the two output terminals of the second pulse modulation type phase-variable two-output transmitter 28 has a third power amplifier 29, a third impedance matching device 30, a third current introduction terminal 31, and a second output terminal. 3 is connected to the first feeding point 21 through the core wire 33 at the end of the vacuum coaxial cable 32. The outer conductor at the end of the third vacuum coaxial cable 32 is connected to the second electrode 4.
The other output terminal of the two output terminals of the second pulse modulation type phase-variable two-output transmitter 28 is a fourth power amplifier 34, a fourth impedance matching device 35, a fourth current introduction terminal 36, and a second output terminal. 4 is connected to the second feeding point 27 via the core wire 38 at the end of the vacuum coaxial cable 37. The outer conductor at the end of the second vacuum coaxial cable 19 is connected to the second electrode 4.
Each of the third power amplifier 29 and the fourth power amplifier 34 is accompanied by a monitor for an output value (traveling wave) and a monitor for a reflected wave returning from the downstream side. In addition, an isolator for protecting the electric circuit of the main body of the first and second power amplifiers 29 and 34 by the reflected wave is attached.
Here, the power supply system for supplying the two outputs of the second phase variable two-output transmitter 28 to the first and second feeding points 21 and 27 by the power amplifiers 29 and 34, respectively, This is called a power supply system.

  Next, a method of manufacturing an amorphous Si film for an a-Si solar cell using the high-frequency plasma generator configured as described above and a plasma surface treatment apparatus (plasma CVD apparatus) configured by the high-frequency plasma generator will be described. In the implementation or application of the present invention, the first and second preliminary film forming steps and the main film forming step are necessary as procedures. The first preliminary film forming step includes the step of determining the phase difference between the two outputs of the first pulse modulation type phase-variable two-output transmitter 15. In order to grasp the set value of the phase difference between the two outputs of the transmitter 28 having the second pulse modulation type variable phase two output, this film forming process is carried out for the purpose of manufacturing the target amorphous Si.

First, in the first preliminary film-forming step, in FIGS. 22 and 23, the substrate 11 is previously set on the second electrode 4, the vacuum pump 10 (not shown) is operated, After removing the impurity gas and the like, the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C. while supplying SiH 4 gas from the discharge gas supply tube 8 at 500 sccm and a pressure of 0.5 Torr (66.5 Pa), for example. To do.
Then, using the first power supply system, high-frequency power, for example, pulse-modulated power of 70 MHz, for example, 400 W in total is supplied to the pair of electrodes 2 and 4.
That is, the phase difference between the two outputs of the first pulse modulation system phase variable 2-output transmitter 15 is set to, for example, zero, pulse modulation pulse width Hw = 400 μsec, and pulse period T0 = 1 msec. The output of the first power amplifier 16 is set to 200 W, for example, and the output is supplied to the first feeding point 21 via the first impedance matching unit 17, the first current introduction terminal 18 and the vacuum coaxial cable 19. And the output of the second power amplifier 22 is set to 200 W, for example, and the output is supplied to the second impedance matching unit 23, the second current introduction terminal 24, and the coaxial for vacuum. It is supplied between the second feeding point 27 and the second electrode 4 via the cable 25.
In this case, the power wave supplied from the feeding points 21 and 27 is attenuated by some influence because the shape of the first electrode as the propagation path is bent at the intermediate point, but is attenuated at the bent portion. The covered dielectric film 92 suppresses power loss in that region. As a result, the above-described standing wave is generated by the power waves W11 (x, t) and W21 (x, t) in the propagation path.
As a result, plasma of the SiH 4 gas is generated, and amorphous Si having a sinusoidal distribution, for example, is deposited on the substrate 11.

In the above-described manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 15 having the first pulse modulation type variable phase two output as a parameter. Then, on the line segment along the U-shape of the rod of the U-shaped electrode 2, the distance from the center point of the U-shaped electrode 2 to the position of the maximum thickness of the sinusoidal film thickness distribution and the first The relationship of the phase difference between the two outputs of the transmitter 15 having the pulse modulation system variable phase 2 output is grasped as data. For example, the phase difference for setting at a position away from the center point of the U-shaped electrode 2 by one-eighth of the wavelength λ in the direction of the first feeding point 21, that is, λ / 8 is, for example, Δθ1. That is understood.
Note that the method of grasping the relationship between the maximum position of the sinusoidal thickness distribution and the phase difference of the output voltage of the first variable-phase two-output transmitter 15a performed here is the measurement of the thickness distribution of the film. The method is not limited to the application method. For example, the spatial distribution of the emission intensity of the generated plasma in the electromagnetic wave propagation direction is measured with an optical sensor, and the relationship between the position of the maximum intensity and the phase difference is grasped. Also good.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Next, as a second preliminary test, in FIGS. 22 and 23, the substrate 11 is previously placed on the second electrode 4, the vacuum pump 10 (not shown) is operated, and impurities in the vacuum vessel 1 are operated. After removing the gas and the like, the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C. while supplying SiH 4 gas from the discharge gas supply tube 8 at, for example, 500 sccm and a pressure of 0.5 Torr (66.5 Pa). .
Then, using the second power supply system, high-frequency power, for example, pulse-modulated power at a frequency of 70 MHz, for example, a total of 400 W is supplied to the pair of electrodes 2 and 4.
That is, the phase difference between the two outputs of the second pulse modulation type phase variable 2-output transmitter 28 is set to, for example, zero, the pulse width of the pulse modulation Hw = 400 μsec, and the pulse period T0 = 1 msec. The output of the first power amplifier 16 is set to 200 W, the output of the third power amplifier 29 is set to 200 W, and the output is set to the third impedance matching device 30, the third current introduction terminal 31, and the vacuum. The power is supplied between the first feeding point 21 and the second electrode 4 via the coaxial cable 32, the output of the fourth power amplifier 34 is set to 200 W, and the output is set to the fourth impedance matching unit. 35, the fourth current introduction terminal 36, and the vacuum coaxial cable 37 are supplied between the second feeding point 27 and the second electrode 4.
In this case, the power wave supplied from the feeding points 21 and 27 is attenuated by some influence because the shape of the first electrode as the propagation path is bent at the intermediate point, but is attenuated at the bent portion. The covered dielectric film 92 suppresses power loss in that region. As a result, the above-mentioned standing wave is generated by the power waves W12 (x, t) and W22 (x, t) in the propagation path.
As a result, plasma of the SiH 4 gas is generated, and amorphous Si having a sinusoidal distribution, for example, is deposited on the substrate 11.

In the above-described manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. As described above, the film thickness distribution of, for example, amorphous Si deposited on the substrate 11 has a sinusoidal distribution due to the generation of a standing wave, which is a phenomenon inherent to VHF plasma. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 28 of the second pulse modulation type variable phase output 2 as a parameter. On the line segment along the U-shape of the rod of the U-shaped electrode 2, the distance from the center point of the U-shaped electrode 2 to the position of the maximum thickness of the sinusoidal film thickness distribution and the second The relationship of the phase difference between the two outputs of the pulse-modulation phase-variable two-output transmitter 28 is grasped as data. For example, the phase difference for setting at a position away from the center point of the U-shaped electrode 2 by one eighth of the wavelength λ in the direction of the second feeding point 27, that is, λ / 8 is, for example, Δθ2. That is understood.
Note that the method of grasping the relationship between the maximum position of the sinusoidal thickness distribution and the phase difference of the output voltage of the first variable-phase two-output transmitter 15a performed here is the measurement of the thickness distribution of the film. The method is not limited to the application method. For example, the spatial distribution of the emission intensity of the generated plasma in the electromagnetic wave propagation direction is measured with an optical sensor, and the relationship between the position of the maximum intensity and the phase difference is grasped. Also good.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Now, in response to the results of the first and second preliminary film forming steps, the main film forming step is started. First, in FIG. 22 and FIG. 23, the substrate 11 is previously set on the second electrode 4 and the vacuum pump 10 (not shown) is operated to remove the impurity gas and the like in the vacuum vessel 1 before supplying the discharge gas. While supplying SiH4 gas from the tube 8 at, for example, 500 sccm and a pressure of 0.5 Torr (66.5 Pa), the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C.
Next, two outputs of the first pulse modulation system variable phase two output transmitter 15 of the constituent members of the first power supply system, for example, a phase difference of a sine wave with a frequency of 70 MHz are used as the first preliminary test data. The detected Δθ1 is set, and the pulse modulation is set such that the pulse width Hw and the period T0 in W11 (t) and W21 (t) shown in FIGS. 11 and 12 are set to, for example, Hw = 400 μsec and T0 = 1 msec. The first and second feeding points 21 and 27 are each supplied with, for example, 200 W of power, and the second pulse modulation type phase-variable two-output transmitter 28 of the second power supply system component. Two outputs, for example, a phase difference of a sine wave having a frequency of 70 MHz, is set to Δθ2 grasped as data of the second preliminary film forming process, and the pulse modulation thereof is W12 (t) and W22 (t) shown in FIGS. In The pulse width Hw and the period T0 are, for example, Hw = 400 μsec and T0 = 1 msec, and a half cycle, that is, T0 / 2 delayed from the pulse rise time of the pulse modulation of W11 (t) and W21 (t). For example, electric power of 200 W is supplied to the first and second feeding points 21 and 27, respectively.
That is, a voltage wave W11 (x, t) having a power of 200 W and a voltage wave W12 (x, t) having a power of 200 W are supplied to the first feeding point 21, and a W21 (x , T) and a voltage wave W22 (x, t) having a power of 200 W are supplied.
Here, the first pulse modulation type phase variable 2 output transmitter 15 and the second pulse modulation type phase variable 2 output transmitter set in the first preliminary film forming step and the second preliminary film forming step, respectively. For example, the values of 28 pulse widths Hw and period T0 can be changed from Hw = 400 μsec to 1 msec or the like, and T0 = 1 msec to 5 msec or the like.

When four voltage waves are supplied between the pair of electrodes 2, 4, as described above, W 11 (x, t) and W 21 (x, t) interfere and the first standing wave W 1 (x , T), and W12 (x, t) and W22 (x, t) interfere to form a second standing wave W2 (x, t). However, W11 (x, t) does not interfere with W12 (x, t) and W22 (x, t) because they are temporally separated. Similarly, W21 (x, t) does not interfere with W12 (x, t) and W22 (x, t).
Therefore, the intensity distribution of the power generated between the pair of electrodes 2 and 4 is the intensity distribution I1 (x, t) of the first standing wave W1 (x, t) and the second standing wave. The intensity distribution I2 (x, t) of the wave W2 (x, t) is superimposed. This is conceptually shown in FIG.
Here, if the center point of the U-shaped electrode 2 is the x-axis origin, and the direction toward the first feeding point 21 on the line segment along the U-shape from the origin is the positive direction, The intensity distribution I1 (x, t) of one standing wave W1 (x, t) is
I1 (x, t) = cos ² {2πx / 2 + 2π (λ / 8) / λ}
= Cos ² {2πx / 2 + π / 4}
The intensity distribution I2 (x, t) of the first standing wave W2 (x, t) is
I2 (x, t) = cos ² {2πx / 2-2π (λ / 8) / λ}
= Cos ² {2πx / 2−π / 4}
The distribution I (x, t) of the strength of power generated between the pair of electrodes 2 and 4 is
I (x, t)
= Cos ² {2πx / 2 + π / 4} + cos ² {2πx / 2−π / 4}
= 1

As a result, the high frequency used in the surface processing apparatus for processing the surface of the substrate disposed in the vacuum vessel using the plasma generated using the power of the output of the high frequency power source whose oscillation frequency belongs to the VHF band or the UHF band. In the plasma generator, the first standing wave and the second standing wave are generated in different positions of antinodes of the standing wave of the electromagnetic wave having an electric field substantially in the same direction as the normal direction of the surface of the substrate. And, by providing means for superimposing the first and second standing waves, it means that it is possible to control the distribution of power intensity between the electrodes, which is indispensable for plasma uniformity. ing.
Further, if the distance between the antinodes of the first and second standing waves is 0.25 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.25λ, a pair of electrodes The power intensity distribution I (x, t) generated between 2 and 4 has a constant value and does not depend on the position in the power propagation direction, and is uniform. This means that it is an epoch-making discovery in the sense that it is possible to provide an apparatus capable of realizing large-area and uniform plasma processing, which is an important issue in the application field of UHF plasma and UHF plasma. Yes.
The distance between the antinodes of the first and second standing waves is 0.22 to 0.28 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.22 to 0.2. If it is 28λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 20% or less.
The distance between the antinodes of the first and second standing waves is 0.238 to 0.263 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.238 to. In the case of H.263λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 10% or less.

In the above process, when SiH 4 gas is turned into plasma, radicals such as SiH 3, SiH 2, and SiH existing in the plasma diffuse due to a diffusion phenomenon and are adsorbed on the surface of the substrate 11, thereby depositing an a-Si film. However, since the distribution of power intensity between the pair of electrodes 2 and 4 is uniform on a time average as described above, the deposited film becomes uniform. This is an epoch-making discovery in the application field of VHF plasma, and its practical value is remarkably large.
That is, one side of the first electrode of the rectangular type that is required in the improvement of the plasma generating device for improving the productivity of the in-line type, multi-chamber type or roll-to-roll type plasma surface treatment apparatus. This can be realized as one new means relating to a means for supplying VHF power only from the vicinity. This means that when the cross section of the main body of the plasma surface treatment apparatus is viewed in a cross section perpendicular to the substrate transport direction, if the cross section is a rectangular cross section, for example, one side of the four sides of the rectangular cross section It is possible to realize a novel power supply means for generating VHF plasma using only the above.
In this example, by setting the distance between the first and second electrodes to about 5 to 40 mm, the amorphous Si film with a glass substrate area of about 1200 mm × 200 mm has a film forming speed of about 1 to 3 nm / s. Film thickness distribution can be within ± 10%.
In this embodiment, since the number of U-shaped first electrodes 2 is one, the width of the substrate size is limited to about 200 mm. However, if the number of the first electrodes is increased, the substrate size is reduced. Of course, the width can be expanded.
It is a well-known technique that microcrystalline Si, thin-film polycrystalline Si, or the like can be formed by optimizing the flow ratio, pressure, and power of SiH4 and H2 in the film forming conditions.
In addition, it is a known technique that can be applied to etching by using NF3, SF6, CF4, CHF3, C4F4, or the like as a discharge gas.

(Example 6)
A high-frequency plasma generation apparatus according to Embodiment 6 of the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus will be described with reference to FIG.
FIG. 24 is a schematic view showing an entire high-frequency plasma generator according to Example 6 and a plasma surface treatment apparatus (plasma CVD apparatus) constituted by the high-frequency plasma generator.
24, the same members as those shown in the first to fifth embodiments are given the same reference numerals.

As shown in FIG. 24, the apparatus according to the present embodiment includes a plurality of, for example, two U-shaped first electrodes described in the fifth embodiment in a plane parallel to the second electrodes. The first and second feeding points are arranged at the respective ends of the plurality of U-shaped first electrodes, and the first and second feeding points of the U-shaped first electrodes are arranged. In point, it has the structure which supplies the output of the said 1st and 2nd electric power supply system.
The U-shaped electrode 2 is formed of a SUS rod having a diameter of about 5 to 20 mm, and the distance from the second electrode can be arbitrarily set to about 5 to 50 mm.
Here, as the first and second power supply systems, one power supply system as shown in FIGS. 13 to 15 of the third embodiment can be used.

  According to this embodiment, it is possible to cope with a large area substrate by installing a large number of U-shaped electrodes as the first electrodes.

(Example 7)
A high-frequency plasma generator of Example 7 relating to the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus will be described with reference to FIG.
FIG. 25 is a schematic view showing an entire high-frequency plasma generator according to Example 7 and a plasma surface treatment apparatus (plasma CVD apparatus) constituted by the high-frequency plasma generator.

As shown in FIG. 25, the apparatus of the present embodiment has first and second feeding points 21 and 27 arranged at the respective ends of the W-shaped first electrode, and the first and second feeding points. It has the structure which supplies the output of the said 1st and 2nd electric power supply system to a point.
That is, the first and second feeding points 21 and 27 arranged on the non-grounded first electrode are arranged in the vicinity of one of the four sides of the rectangular flat plate ground electrode as the second electrode 4. And the shape of the first electrode has a W-shape formed by folding a single rod-shaped conductor so as to be included in a plane parallel to the first electrode, and preferably Is that the total length of the W-shape is one half of the wavelength λ of the power used, that is, an integral multiple of λ / 2. In addition, the bent portion of the W-shaped electrode is characterized by being covered with a dielectric such as alumina.
The W-shaped electrode 2 is formed of a SUS rod having a diameter of about 5 to 20 mm, and the distance from the second flat plate electrode can be arbitrarily set at 5 to 50 mm.

  According to the present embodiment, it is expected that it is possible to easily cope with a large-area substrate as compared with the case where a U-shaped electrode is used.

(Example 8)
A high-frequency plasma generation apparatus according to an eighth embodiment of the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus will be described with reference to FIG. Reference is also made to FIG.
FIG. 26 is a schematic diagram showing an entire high-frequency plasma generator according to Example 8 and a plasma surface treatment apparatus (plasma CVD apparatus) constituted by the high-frequency plasma generator. FIG. 27 is an explanatory view showing an applied type of a configuration relating to a pair of electrodes used as components of the apparatus shown in FIG.
26 and 27, the same members as those shown in the first to seventh embodiments are denoted by the same reference numerals, and the description thereof is omitted.

The apparatus of the present embodiment is a plasma surface treatment apparatus for a cylindrical substrate, and the configuration thereof includes a plurality of W-shaped first electrodes, for example, two cylindrical shapes as shown in FIG. The first and second feeding points 21 and 27 are provided at the respective end portions of the plurality of W-shaped first electrodes. Arranged and configured to supply the outputs of the first and second power supply systems to the first and second feeding points 21 and 27 of the respective W-shaped first electrodes. It is. Preferably, the total length of each W-shaped electrode is a half of the wavelength λ of the power used, that is, an integral multiple of λ / 2.
Naturally, a plasma surface treatment apparatus in which the W-shaped electrode is replaced with a U-shaped electrode is also conceivable.
The W-shaped electrode 2 is formed of a SUS rod having a diameter of about 5 to 20 mm, and the distance from the second flat plate electrode can be arbitrarily set at 5 to 50 mm.

According to the apparatus of the present embodiment, it is possible to easily cope with the case where the shape of the substrate is cylindrical.
In addition, it is naturally possible to use the coil-type electrode shown in FIG. 27 as the first electrode in the apparatus configuration shown in FIG. The coil type electrode can be used when there is no particular restriction on the device configuration.

Example 9
A high-frequency plasma generation apparatus according to Embodiment 9 of the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus will be described with reference to FIG. Reference is also made to FIGS. 3 to 6, 11 and 12.
FIG. 28 is a schematic view showing an entire high-frequency plasma generator according to Example 9 and a plasma surface treatment apparatus (plasma CVD apparatus) constituted by the high-frequency plasma generator.

First, the configuration of the apparatus will be described. However, Examples 1 to 8 are used.
The same members as those shown in FIG.
The apparatus of the present embodiment divides a rectangular flat conductor into two by a W-shaped slit, and uses one conductor as a first electrode, the other as a second electrode, and the W-shaped slit. It has a structure in which a feeding point is arranged at the end.
The slit may have a shape other than the W shape, for example, a U shape and a zigzag shape. Further, the shape of the conductor is not limited to a rectangular flat plate. For example, when the shape of the substrate is cylindrical, it can be made cylindrical correspondingly.

In FIG. 28, reference numeral 91 is a slit. Here, a W-shaped slit is used. The width of the slit is about 2 mm to 50 mm, for example, 8 mm in consideration of the pressure condition described later: 0.5 Torr (66.5 Pa).
Reference numeral 2 is a first electrode, and reference numeral 4 is a second electrode. The size of the first and second electrodes is, for example, about 1400 mm × 200 mm with a pair of outer dimensions. Reference numeral 21 is a first feeding point, and reference numeral 27 is a second feeding point, which are arranged at the ends of the W-shaped slit 91 in an opposed manner. Reference numeral 90 denotes a discharge gas passage hole, which is installed on the first and second electrodes. The diameter of the hole is preferably about 1 to 5 mm, and the aperture ratio is preferably about 50% or more.
In FIG. 28, one of the two output terminals of the first pulse modulation type phase-variable two-output transmitter 15 is a first power amplifier 16, a first impedance matching unit 17, a first current introduction. The terminal 18 and the core wire 20 at the end of the first vacuum coaxial cable 19 are connected to the first feeding point 21. The outer conductor at the end of the first vacuum coaxial cable 19 is connected to the second electrode 4.
The other output terminal of the two output terminals of the first pulse modulation type phase-variable two-output transmitter 15 is the second power amplifier 22, the second impedance matching unit 23, the second current introduction terminal 24, and the second output terminal. 2 is connected to a second feeding point 27 via a core wire 26 at the end of the vacuum coaxial cable 25. The outer conductor at the end of the second vacuum coaxial cable 19 is connected to the second electrode 4.
Each of the first power amplifier 16 and the second power amplifier 22 is attached with a monitor for an output value (traveling wave) and a monitor for a reflected wave returning from the downstream side. In addition, an isolator for protecting the electric circuit of the first and second power amplifiers 16 and 22 by the reflected wave is attached.
Here, the first power supply system for supplying the two outputs of the first phase variable two-output transmitter 15 to the first and second feeding points 21 and 27 by the power amplifiers 16 and 22, respectively, is the first power supply system. This is called a power supply system.

In FIG. 28, one of the two output terminals of the second pulse modulation type phase-variable two-output transmitter 28 includes a third power amplifier 29, a third impedance matching device 30, and a third current introduction. The terminal 31 and the core wire 33 at the end of the third vacuum coaxial cable 32 are connected to the first feeding point 21. The outer conductor at the end of the third vacuum coaxial cable 32 is connected to the second electrode 4.
The other output terminal of the two output terminals of the second pulse modulation type phase-variable two-output transmitter 28 is a fourth power amplifier 34, a fourth impedance matching device 35, a fourth current introduction terminal 36, and a second output terminal. 4 is connected to the second feeding point 27 via the core wire 38 at the end of the vacuum coaxial cable 37. The outer conductor at the end of the second vacuum coaxial cable 19 is connected to the second electrode 4.
The third power amplifier 29 and the fourth power amplifier 34 are each accompanied by a monitor for an output value (traveling wave) and a monitor for a reflected wave reflected and returned from the downstream side. In addition, an isolator for protecting the electric circuit of the main body of the first and second power amplifiers 29 and 34 by the reflected wave is attached.
Here, a power supply system for supplying the two outputs of the second pulse modulation type phase variable 2-output transmitter 28 to the first and second feeding points 21 and 27 by the power amplifiers 29 and 34, respectively, is provided. This is called a second power supply system.

  Next, a method for manufacturing an amorphous Si film for an a-Si solar cell using the plasma surface treatment apparatus having the above configuration will be described. In the implementation or application of the present invention, the first and second preliminary film forming steps and the main film forming step are necessary as procedures. The first preliminary film forming step includes the step of determining the phase difference between the two outputs of the first pulse modulation type phase-variable two-output transmitter 15. In order to grasp the set value of the phase difference between the two outputs of the transmitter 28 having the second pulse modulation type variable phase two output, this film forming process is carried out for the purpose of manufacturing the target amorphous Si.

First, in the first preliminary film forming step, in FIG. 28, the substrate 11 is previously set on the second electrode 4 and the vacuum pump 10 (not shown) is operated, so that the impurity gas in the vacuum vessel 1 and the like. Then, the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C. while supplying SiH 4 gas from the discharge gas supply tube 8 at 500 sccm and a pressure of 0.5 Torr (66.5 Pa), for example.
Then, using the first power supply system, ultra high frequency power, for example, power at a frequency of 70 MHz, for example, 400 W in total is supplied to the pair of electrodes 2 and 4.
That is, the phase difference between the two outputs of the first pulse modulation system variable-phase two-output transmitter 15, for example, a pulse-modulated sine wave having a frequency of 70 MHz, is set to, for example, zero, and the first power amplifier 16 The output is set to 200 W, for example, and the output is connected between the first feeding point 21 and the second electrode 4 via the first impedance matching unit 17, the first current introduction terminal 18 and the vacuum coaxial cable 19. And the output of the second power amplifier 22 is set to 200 W, for example, and the output is passed through the second impedance matching unit 23, the second current introduction terminal 24, and the vacuum coaxial cable 25 to 2 between the second feeding point 27 and the second electrode 4.
Here, typical examples of power supplied to the first and second feeding points 21 and 27 are shown as W11 (t) and W21 (t) in FIGS. W11 (t) and W21 (t) are sine waves having a pulse width Hw and a pulse modulation with a period T0, for example, 70 MHz. The pulse width Hw and period T0 are set to arbitrary values, for example, Hw = 400 μsec and period T0 = 1 msec, by a regulator attached to the first pulse modulation system phase variable 2-output transmitter 15.
In this case, the power wave supplied from the feeding points 21 and 27 is attenuated slightly because the W-shaped slit that is the propagation path is bent in the middle, but is attenuated but is covered by the bent portion. The dielectric 92 that is present suppresses power loss in that region. As a result, the above-described standing wave is generated by the power waves W11 (x, t) and W21 (x, t) in the propagation path.
As a result, plasma of the SiH 4 gas is generated, and amorphous Si having a sinusoidal distribution is deposited on the substrate 11.

In the above-described manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 15 having the first pulse modulation type variable phase two output as a parameter. Then, in the length direction of the W-shaped slit 91, the distance from the center point of the W-shaped slit 91 to the position of the maximum thickness of the sinusoidal film thickness distribution and the first pulse modulation system phase variable 2 output The relationship between the phase differences between the two outputs of the transmitter 15 is grasped as data. For example, the phase difference for setting at a position away from the central point of the W-shaped slit 91 in the direction of the first feeding point 21 by an eighth wavelength λ, that is, λ / 8 is, for example, Δθ1. That is understood.
Note that the method of grasping the relationship between the maximum position of the sinusoidal thickness distribution and the phase difference of the output voltage of the first variable-phase two-output transmitter 15a performed here is the measurement of the thickness distribution of the film. The method is not limited to the application method. For example, the spatial distribution of the emission intensity of the generated plasma in the electromagnetic wave propagation direction is measured with an optical sensor, and the relationship between the position of the maximum intensity and the phase difference is grasped. Also good.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Next, as a second preliminary test, in FIG. 24, the substrate 11 is set on the second electrode 4 in advance, the vacuum pump 10 (not shown) is operated, and the impurity gas in the vacuum vessel 1 is removed. After the removal, the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C. while supplying SiH 4 gas from the discharge gas supply tube 8 at, for example, 500 sccm and a pressure of 0.5 Torr (66.5 Pa).
Then, using the second power supply system, ultra high frequency power, for example, power at a frequency of 70 MHz, for example, a total of 400 W is supplied to the pair of electrodes 2 and 4.
That is, the phase difference between the two outputs of the second pulse modulation type phase-variable two-output transmitter 28, for example, the pulse-modulated sine wave of 70 MHz, is set to, for example, zero, and the third power amplifier 29 The output is set to 200 W, and the output is connected between the first feeding point 21 and the second electrode 4 via the third impedance matching unit 30, the third current introduction terminal 31 and the vacuum coaxial cable 32. In addition, the output of the fourth power amplifier 34 is set to 200 W, and the output is passed through the fourth impedance matching unit 35, the fourth current introduction terminal 36, and the vacuum coaxial cable 37 to the second Supply is performed between the feeding point 27 and the second electrode 4.
Here, typical examples of power supplied to the first and second feeding points 21 and 27 are shown as W12 (t) and W22 (t) in FIGS. W12 (t) and W22 (t) are sine waves of ultrahigh frequency, for example, 70 MHz, which are pulse-modulated with a pulse width Tw and a period T0.
The pulse width Tw and the period T0 are set to arbitrary values, for example, Tw = 400 μsec and the period T0 = 1 msec, by a regulator attached to the transmitter 28 of the second pulse modulation type phase variable 2 output.
In this case, the power wave supplied from the feeding points 21 and 27 is attenuated slightly because the W-shaped slit that is the propagation path is bent in the middle, but is attenuated but is covered by the bent portion. The dielectric 92 that is present suppresses power loss in that region. As a result, the above-mentioned standing wave is generated by the power waves W12 (x, t) and W22 (x, t) in the propagation path.
As a result, plasma of the SiH 4 gas is generated, and amorphous Si having a sinusoidal distribution, for example, is deposited on the substrate 11.

In the above-described manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 28 having the second phase variable and two outputs as a parameter. Then, in the length direction of the W-shaped slit 91, the distance from the center point of the W-shaped slit 91 to the position of the maximum thickness of the sinusoidal film thickness distribution and the transmission of the second pulse modulation method phase variable 2 output The relationship of the phase difference between the two outputs of the device 28 is grasped as data. For example, the phase difference for setting at a position away from the central point of the W-shaped slit 91 in the direction of the second feeding point 27 by an eighth wavelength λ, that is, λ / 8 is, for example, Δθ2. It is understood.
Note that the method of grasping the relationship between the maximum position of the sinusoidal thickness distribution and the phase difference of the output voltage of the first variable-phase two-output transmitter 15a performed here is the measurement of the thickness distribution of the film. The method is not limited to the application method. For example, the spatial distribution of the emission intensity of the generated plasma in the electromagnetic wave propagation direction is measured with an optical sensor, and the relationship between the position of the maximum intensity and the phase difference is grasped. Also good.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Now, in response to the results of the first and second preliminary film forming steps, the main film forming step is started. First, in FIG. 28, the substrate 11 is set on the second electrode 4 in advance, and the vacuum pump 10 (not shown) is operated to remove the impurity gas and the like in the vacuum vessel 1, and then from the discharge gas supply pipe 8. While supplying SiH4 gas at, for example, 500 sccm and pressure of 0.5 Torr (66.5 Pa), the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C.
Next, two outputs of the first pulse modulation system variable phase two output transmitter 15 of the constituent members of the first power supply system, for example, a phase difference of a sine wave with a frequency of 70 MHz are used as the first preliminary test data. The detected Δθ1 is set, and the pulse modulation is set such that the pulse width Hw and the period T0 in W11 (t) and W21 (t) shown in FIGS. 11 and 12 are set to, for example, Hw = 400 μsec and T0 = 1 msec. The first and second feeding points 21 and 27 are each supplied with, for example, 200 W of power, and the second pulse modulation type phase-variable two-output transmitter 28 of the second power supply system component. Two outputs, for example, a phase difference of a sine wave having a frequency of 70 MHz, is set to Δθ2 grasped as data of the second preliminary film forming process, and the pulse modulation thereof is W12 (t) and W22 (t) shown in FIGS. In The pulse width Hw and the period T0 are, for example, Hw = 400 μsec and T0 = 1 msec, and a half cycle, that is, T0 / 2 delayed from the pulse rise time of the pulse modulation of W11 (t) and W21 (t). For example, electric power of 200 W is supplied to the first and second feeding points 21 and 27, respectively.
That is, a voltage wave W11 (x, t) having a power of 200 W and a voltage wave W12 (x, t) having a power of 200 W are supplied to the first feeding point 21, and a W21 (x , T) and a voltage wave W22 (x, t) having a power of 200 W are supplied.
Here, the first pulse modulation type phase variable 2 output transmitter 15 and the second pulse modulation type phase variable 2 output transmitter set in the first preliminary film forming step and the second preliminary film forming step, respectively. For example, the values of 28 pulse widths Hw and period T0 can be changed from Hw = 400 μsec to 1 msec or the like, and T0 = 1 msec to 5 msec or the like.

When four voltage waves are supplied between the pair of electrodes 2, 4, as described above, W 11 (x, t) and W 21 (x, t) interfere and the first standing wave W 1 (x , T), and W12 (x, t) and W22 (x, t) interfere to form a second standing wave W2 (x, t). However, W11 (x, t) does not interfere with W12 (x, t) and W22 (x, t) because they are temporally separated. Similarly, W21 (x, t) does not interfere with W12 (x, t) and W22 (x, t).
Accordingly, considering a general film formation time of several seconds or longer, which is significantly longer than the pulse modulation period T0, the distribution of the strength of power generated between the pair of electrodes 2 and 4 is the first standing wave. The intensity distribution I1 (x, t) of W1 (x, t) and the intensity distribution I2 (x, t) of the second standing wave W2 (x, t) are superimposed. This is conceptually shown in FIG.
Here, if the center point of the substrate, that is, the line connecting the apex of the wedge 90 and the slit is the origin of the x axis, and the direction from the origin to the first feeding point 21 is the positive direction, the first constant is defined. The intensity distribution I1 (x, t) of the standing wave W1 (x, t) is
I1 (x, t) = cos ² {2πx / 2 + 2π (λ / 8) / λ}
= Cos ² {2πx / 2 + π / 4}
The intensity distribution I2 (x, t) of the second standing wave W2 (x, t) is
I2 (x, t) = cos ² {2πx / 2-2π (λ / 8) / λ}
= Cos ² {2πx / 2−π / 4}
The distribution I (x, t) of the strength of power generated between the pair of electrodes 2 and 4 is
I (x, t)
= Cos ² {2πx / 2 + π / 4} + cos ² {2πx / 2−π / 4}
= 1

As a result, if the distance between the antinodes of the first and second standing waves is 0.25 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.25λ, The intensity distribution I (x, t) of the power generated between the electrodes 2 and 4 is constant, independent of the position in the power propagation direction, and is uniform. This means that it is an epoch-making discovery in the sense that it is possible to provide an apparatus capable of realizing large-area and uniform plasma processing, which is an important issue in the application field of UHF plasma and UHF plasma. Yes.
The distance between the antinodes of the first and second standing waves is 0.22 to 0.28 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.22 to 0.2. If it is 28λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 20% or less.
The distance between the antinodes of the first and second standing waves is 0.238 to 0.263 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.238 to. In the case of H.263λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 10% or less.

In the above process, when SiH 4 gas is turned into plasma, radicals such as SiH 3, SiH 2, and SiH existing in the plasma diffuse due to a diffusion phenomenon and are adsorbed on the surface of the substrate 11, thereby depositing an a-Si film. However, since the distribution of power intensity between the pair of electrodes 2 and 4 is uniform on a time average as described above, the deposited film becomes uniform. This is an epoch-making discovery in the application field of VHF plasma, and its practical value is remarkably large.
That is, one side of the first electrode of the rectangular type that is required in the improvement of the plasma generating device for improving the productivity of the in-line type, multi-chamber type or roll-to-roll type plasma surface treatment apparatus. This can be realized as one new means relating to a means for supplying VHF power only from the vicinity. This means that when the cross section of the main body of the plasma surface treatment apparatus is viewed in a cross section perpendicular to the substrate transport direction, if the cross section is a rectangular cross section, for example, one side of the four sides of the rectangular cross section It is possible to realize a novel power supply means for generating VHF plasma using only the above.
In this example, by setting the distance between the installation surface of the first and second electrodes and the substrate to about 5 to 40 mm, the amorphous Si film formation with a glass substrate size of about 1200 mm × 200 mm is performed at a film formation rate of 1 to 1. Film formation with a film thickness distribution within ± 10% is possible at about 3 nm / s.
In this embodiment, since the pair of electrodes 2 and 4 including the W-shaped slit 91 is one set, the width of the substrate size is limited to about 200 mm, but the pair of electrodes including the W-shaped slit 91 is included. It goes without saying that the substrate size width can be increased by increasing the number of electrodes 2 and 4.
It is a well-known technique that microcrystalline Si, thin-film polycrystalline Si, or the like can be formed by optimizing the flow ratio, pressure, and power of SiH4 and H2 in the film forming conditions.
In addition, it is a known technique that can be applied to etching by using NF3, SF6, CF4, CHF3, C4F4, or the like as a discharge gas.

(Example 10)
A high-frequency plasma generator according to Example 10 of the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus will be described with reference to FIG. 2 to 6, 11 and 12 are also referred to.
FIG. 29 is a schematic view showing an entire high-frequency plasma generator according to Example 10 and a plasma surface treatment apparatus (plasma CVD apparatus) constituted by the high-frequency plasma generator.

First, the configuration of the apparatus will be described. However, the same members as those shown in Examples 1 to 9 are denoted by the same reference numerals, and description thereof is omitted.
In FIG. 29, reference numeral 70 denotes a high-frequency oscillator, which generates a sine wave signal having a frequency of VHF band or UHF band, for example, 10 MHz to 300 MHz. Reference numerals 71, 72, and 73 denote first, second, and third distributors, respectively. The first distributor 71 distributes the output of the high-frequency transmitter 70 into two. The second distributor 72 distributes the output of the first gate circuit device 74 described later into two. The third distributor 73 distributes the output of the second gate circuit device 75 described later into two.
Reference numerals 74 and 75 are first and second gate circuit devices, respectively, which are in a conductive state between the input terminal and the output terminal only during the time when the pulse voltage of the pulse generator 80 described later is applied. To. In addition, it is in a disconnected state when no pulse voltage is applied. Reference numerals 76 and 77 are first and second phase shifters. The first phase shifter 76 has a function of delaying the phase of the pulse-modulated high frequency signal input to its input terminal, and the amount of delay is controlled by the output of a phase difference detector 78 described later. The second phase shifter 77 has a function of delaying the phase of the pulse-modulated high-frequency signal input to its input terminal, and the delay amount is controlled by the output of a phase difference detector 79 described later.
Reference numerals 78 and 79 are first and second phase difference detectors, respectively. The first phase difference detector 78 detects the phase difference between the output voltages of the first and second impedance matching units 17 and 23, and uses a voltage proportional to the phase difference as a control signal for the phase shifter 76. Transmit to the phase shifter 76. The second phase difference detector 79 detects the phase difference between the output voltages of the third and fourth impedance matching units 30 and 35, and uses a voltage proportional to the phase difference as a control signal for the phase shifter 77. Transmit to the phase shifter 77. Each of the first and second phase difference detectors 78 and 79 is provided with a phase adjustment dial that can arbitrarily control the phases of the first and second phase shifters 76 and 77, respectively. The phase of the sine wave signal output from the first and second phase shifters 76 and 77 can be arbitrarily adjusted.
Reference numeral 80 is a two-output pulse transmitter, whose first output terminal outputs a pulse voltage having an arbitrary pulse width Hw and an arbitrary period T0, and its second output terminal is output from the first output terminal. A pulse voltage having the same pulse width Hw and period T0 as the pulse voltage to be output and a phase delayed by a half period, that is, T0 / 2 is output. The pulse voltage from the first output terminal is transmitted to the first gate circuit device 74 as a control signal for the first gate circuit device 74. The pulse voltage from the second output terminal is transmitted to the second gate circuit device 75 as a control signal for the second gate circuit device 75.

In FIG. 29, an ultra-high frequency sine wave signal output from the output terminal of the high frequency oscillator 70, for example, a 60 MHz sine wave signal, is divided into two by the first distributor 71, and one of the outputs is the first one. Two distributions are performed by the second distributor 72 via the gate circuit device 74. One of the outputs is amplified by the first power amplifier 16 and is supplied to the first power supply via the first impedance matching unit 17, the first current introduction terminal 18, and the core wire 20 of the vacuum coaxial cable 19. Provided to point 21.
The first gate circuit device 74 is ON / OFF controlled by an arbitrary pulse width Hw transmitted from the output terminal of the pulse transmitter 80 and a pulse voltage having an arbitrary period T0.
Here, typical examples of the pulse voltage are shown as W11 (t) and W21 (t) in FIGS.
The other output of the second distributor 72 is connected to the second power amplifier 22, the second impedance matching unit 23, the second current introduction terminal 24, and the second vacuum coaxial cable 25 via the phase shifter 76. Is supplied to the second feeding point 27 via the core wire 26.
The phase shifter 76 is controlled by a voltage proportional to the phase difference between the output voltages of the first and second impedance matchers 17 and 23 detected by the first phase difference detector 78, and is input to the phase shifter 76. The phase of the received sine wave signal is delayed and transmitted to the second power amplifier 22 on the downstream side.
The phase of the phase shifter 76 can be arbitrarily controlled manually with a phase adjustment dial attached to the first phase difference detector 78.

In FIG. 29, the other of the outputs divided into two by the first distributor 71 is divided into two by the third distributor 73 via the second gate circuit device 75. One of the outputs is amplified by the third power amplifier 29, and is supplied to the first power supply via the third impedance matching unit 30, the third current introduction terminal 36, and the core wire 32 of the vacuum coaxial cable 31. Provided to point 21.
The second gate circuit device 75 is on / off controlled by an arbitrary pulse width Hw transmitted from the output terminal of the pulse transmitter 80 and a pulse voltage having an arbitrary period T0. Here, typical examples of the pulse voltage are shown as W12 (t) and W22 (t) in FIGS. W12 (t) and W22 (t) rise at a half cycle, that is, a time delayed by T0 / 2 compared to W11 (t) and W21 (t).
The other output of the third distributor 73 is connected to a fourth power amplifier 34, a fourth impedance matching unit 35, a fourth current introduction terminal 36, and a fourth vacuum coaxial cable 37 via a phase shifter 77. Is supplied to the second feeding point 27 via the core wire 38.
The phase shifter 77 is controlled by a voltage proportional to the phase difference between the output voltages of the third and fourth impedance matching units 30 and 35 detected by the second phase difference detector 79, and is input to the phase shifter 77. The phase of the received sine wave signal is delayed and transmitted to the fourth power amplifier 34 on the downstream side. The phase of the phase shifter 77 can be arbitrarily controlled manually with a phase adjustment dial attached to the second phase difference detector 79.

Here, the high-frequency oscillator 70, the first, second, and third distributors 71, 72, 73, the first and second gate circuit devices 74, 75, and the first and second phase shifters 76. 77, first phase shifter 76, second phase shifter 77, first and second phase difference detectors 78 and 79, two-output pulse transmitter 80, and first power amplifier 16 The first impedance matching unit 17, the first current introduction terminal 18, the first vacuum coaxial cable 19, the second power amplifier 22, the second impedance matching unit 23, and the second current introduction. A terminal 24, a second vacuum coaxial cable 25, a third power amplifier 29, a third impedance matching device 30, a third current introduction terminal 31, a third vacuum coaxial cable 32, Fourth power amplifier 34 and fourth impedance adjustment A vessel 35, the power supply system of the composed fourth current introduction terminal 36 and the fourth coaxial cable 37 for the vacuum, is called a high-frequency power supply device.
Here, the plasma generation system including the high-frequency power supply device, the pair of electrodes 24, and the feeding point 2127 is referred to as a plasma generation device.

Next, a method for forming an amorphous Si film for an a-Si solar cell using the plasma generator having the above-described structure and a plasma surface treatment apparatus (plasma CVD apparatus) having the plasma generator will be described.
In the implementation or application of the present invention, the first and second preliminary film forming steps and the main film forming step are necessary as procedures. In the first preliminary film forming step, a first phase difference detector that measures and controls a phase difference between an output voltage of the first impedance matcher 17 and an output voltage of the second impedance matcher 23. In order to grasp the phase setting value of the first phase control system comprising 78 and the first phase shifter 76, the second preliminary film-forming step includes the output voltage of the third impedance matching unit 30 and the first 4 to measure the phase difference of the voltage of the output of the impedance matching unit 35 and to grasp the phase setting value of the second phase control system comprising the second phase difference detector 79 and the second phase shifter 77 to be controlled. In addition, this film-forming process is performed for the production of the target amorphous Si.

  First, in FIG. 29 and FIG. 2, the substrate 11 is set on the second electrode 4 in advance and the vacuum pump 10 (not shown) is operated in the first and second preliminary film forming steps. After removing the impurity gas and the like in 1, the substrate temperature is in the range of 80 to 350 ° C. while supplying SiH 4 gas from a discharge gas supply tube 8 (not shown) at, for example, 250 sccm and a pressure of 0.5 Torr (66.5 Pa). For example, it is maintained at 180 ° C.

Next, high-frequency power is supplied to the pair of electrodes 2 and 4 using a part of the high-frequency power supply device.
That is, the sine wave output of the high-frequency transmitter 70 pulse-modulated by the first gate circuit device 74 controlled by the pulse voltage of the two-output pulse transmitter 80 is divided into two by the second distributor 72. In this case, the frequency of the sine wave output of the high-frequency transmitter 70 can be arbitrarily set in the range of 10 MHz to 300 MHz. For example, the frequency is set to 60 MHz. Further, the pulse width Hw and pulse period T0 of the sine wave output of the pulse-modulated ultrahigh-frequency transmitter 70 can be arbitrarily set. For example, the pulse width Hw = 400 μsec and the pulse period T0 = 1 msec are set. The
One signal divided into two by the second distributor 72 is amplified by the first power amplifier 16 to obtain, for example, a power of 200 W, and the power is supplied to the first impedance matching device 17, the first current introduction terminal 18, and the like. The first feeding point 21 is supplied via the core wire 20 of the first vacuum coaxial cable 19.
The other signal divided into two by the second distributor 72 is amplified by the second power amplifier 22 via the first phase shifter 76, for example, is set to 200 W, and the power is supplied to the second impedance matching unit 23. The second current introduction terminal 24 and the core wire 26 of the second vacuum coaxial cable 25 are supplied to the second feeding point 27. In this case, the phase difference between the voltages of the power supplied to the first and second feeding points 21 and 27 is the output voltage of the first impedance matching unit 17 and the output of the second impedance matching unit 23. Is controlled by a first phase control system comprising a first phase difference detector 78 and a first phase shifter 76 for measuring and controlling the phase difference of the voltage, and an arbitrary phase difference can be set. Set the phase difference to zero degrees.
The waveform of the pulse-modulated power supplied to the first feeding point 21 is conceptually shown as W11 (t) in FIGS. Further, the waveform of the pulse-modulated power supplied to the second feeding point 27 is conceptually shown as W21 (t) in FIGS.
In this case, by adjusting the first impedance matching unit 17 and the second impedance matching unit 23, the reflected wave of the supplied power does not return to the upstream side of the respective impedance matching units 17 and 23. Can do.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference of the voltage of the power supplied to the first and second feeding points as a parameter.
Then, in the length direction of the first electrode 2, the relationship between the distance from the center point of the substrate 11 to the position of the maximum thickness of the sine film thickness distribution and the phase difference is grasped as data. For example, it is understood that the phase difference for setting a position that is one-eighth of the wavelength λ from the center point of the substrate 11 in the direction of the first feeding point 21, that is, λ / 8, is, for example, Δθ1. Is done.
Note that the method of grasping the relationship between the maximum position of the sinusoidal thickness distribution and the phase difference of the output voltage of the first variable-phase two-output transmitter 15a performed here is the measurement of the thickness distribution of the film. The method is not limited to the application method. For example, the spatial distribution of the emission intensity of the generated plasma in the electromagnetic wave propagation direction is measured with an optical sensor, and the relationship between the position of the maximum intensity and the phase difference is grasped. Also good.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

By the way, the voltage wave of the power supplied from the first and second feeding points 21 and 27 is oscillated from the same power source and propagates between the electrodes. That is, two electromagnetic waves having an electric field in substantially the same direction as the normal direction of the surface of the substrate 11 are generated between the first electrode 2 and the second electrode 4, and both propagate from directions opposite to each other. Since they overlap each other, an interference phenomenon occurs. This will be described with reference to FIGS.
The direction substantially the same as the normal direction of the surface of the substrate 11 means a direction having a cosine value of 0.7 or more, that is, a direction within about 45 degrees from the normal line.
2 and 3, the distance in the direction from the first feeding point 21 to the second feeding point 27 is x, and the voltage wave propagating in the positive direction of x is W11 (x, t), in the negative direction of x. Assuming that a propagating voltage wave, that is, a voltage wave propagating from the second feeding point 27 toward the first feeding point 21, is W21 (x, t), it is expressed as follows.
W11 (x, t) = V1 · sin (ωt + 2πx / λ)
W21 (x, t) = V1 · sin {ωt−2π (x−L0) / λ + Δθ}
Where V1 is the amplitude of the voltage wave, ω is the angular frequency of the voltage, λ is the wavelength of the voltage wave, t is time, L0 is the interval between the first and second feeding points, and Δθ is supplied from the first feeding point 21. The phase difference between the voltage wave of the electric power and the voltage wave of the electric power supplied from the second feeding point 27. A composite wave W1 (x, t) of these two voltage waves is expressed by the following equation.
W1 (x, t) = W11 (x, t) + W21 (x, t)
= 2 · V1cos {2π (x−L0 / 2) / λ−Δθ / 2} · sin {ωt + (πL0 / λ + Δθ / 2)
The synthesized wave W1 (x, t) is conceptually shown in FIG. In FIG. 4, when Δθ = 0, the intensity of the generated plasma is strong in the central portion (x = L0 / 2) between the feeding points, and decreases as the distance from the central portion increases. When Δθ> 0, the strong plasma portion moves to one feeding point side, and when Δθ <0, it moves to the other feeding point side.
Here, the voltage waves of the power supplied to the first and second feeding points 21 and 27 are referred to as W11 (x, t) and W21 (x, t), respectively. Further, the combined wave of the two voltage waves is referred to as a first standing wave W1 (x, t).

By the way, the strength of power between the pair of electrodes is proportional to the square of the amplitude value of the first standing wave W1 (x, t) of the voltage. That is, the power intensity I1 (x, t) is
I1 (x, t) ∝cos ² {2π (x−L0 / 2) / λ−Δθ / 2}
It is expressed. This I1 (x, t) is conceptually shown in FIG.
FIG. 5 shows that it is difficult to obtain a uniform intensity plasma in the generation of the VHF plasma. The uniformity of the plasma between the pair of electrodes is, for example, in the range of −0.05 to + 0.05λ (ie, the distance in the power propagation direction when the intensity is in the range of 0.9 to 1.0 (that is, This indicates that the range in which the film thickness is uniform is limited to a length of 0.1λ).
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.
Further, the distance from the center point of the substrate acquired in the first preliminary film forming step to the position of the maximum thickness of the sinusoidal film thickness distribution and the first and second feeding points 21 and 27 are supplied. The position of the maximum thickness of the film thickness distribution can be set, for example, at a position that is one-eighth of the wavelength λ from the center point of the substrate, that is, λ / 8, based on the data indicating the relationship of the phase difference of the power voltage. it can.

  Next, in the second preliminary film forming step, as in the first preliminary film forming step, in FIG. 29 and FIG. 2, the substrate 11 is previously set on the second electrode 4 and illustrated. After operating the vacuum pump 10 and removing the impurity gas and the like in the vacuum vessel 1, while supplying SiH4 gas from a discharge gas supply pipe 8 (not shown) at, for example, 250 sccm and a pressure of 0.5 Torr (66.5 Pa), The substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C.

Next, high-frequency power is supplied to the pair of electrodes 2 and 4 using a part of the high-frequency power supply device.
That is, the third distributor 73 distributes the sine wave output of the high-frequency transmitter 70 that is pulse-modulated by the second gate circuit device 75 controlled by the pulse voltage of the two-output pulse transmitter 80. The frequency of the sine wave output of the high-frequency transmitter 70 is the same frequency as that of the first preliminary film forming step, for example, the frequency is 60 MHz. Further, the pulse width Hw and the pulse period T0 of the sine wave output of the pulse-modulated ultrahigh-frequency transmitter 70 are the same as those in the first preliminary film forming process, for example, the pulse width Hw = 400 μsec, the pulse period T0 = Although it is set to 1 ms, the rise time of the pulse is set to a half cycle delay.
One signal divided into two by the third distributor 73 is amplified by the third power amplifier 29 to obtain, for example, a power of 200 W, and the power is supplied to the third impedance matching device 30, the third current introduction terminal 36, and the like. The power is supplied to the first feeding point 21 via the core wire 32 of the third vacuum coaxial cable 31.
The other signal divided into two by the third distributor 72 is amplified by the fourth power amplifier 34 via the second phase shifter 77, for example, to be 200 W, and the power is converted to the fourth impedance matching unit 35. The second current feeding point 27 is supplied via the fourth current introduction terminal 36 and the core wire 38 of the fourth vacuum coaxial cable 37. In this case, the phase difference between the voltages of the power supplied to the first and second feeding points 21 and 27 is the voltage of the output of the third impedance matching unit 30 and the output of the fourth impedance matching unit 35. Is controlled by a second phase control system comprising a second phase difference detector 79 and a second phase shifter 77 for measuring and controlling the phase difference of the voltage, and an arbitrary phase difference can be set. Set the phase difference to zero degrees.
The waveform of the pulse-modulated power supplied to the first feeding point 21 is conceptually shown as W12 (t) in FIGS. Further, the waveform of the pulse-modulated power supplied to the second feeding point 27 is conceptually shown as W22 (t) in FIGS.
In this case, by adjusting the third impedance matcher 30 and the fourth impedance matcher 35, the reflected wave of the supplied power is prevented from returning to the upstream side of the respective impedance matchers 30 and 35. Can do.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. As described above, the film thickness distribution of, for example, amorphous Si deposited on the substrate 11 has a sinusoidal distribution due to the generation of a standing wave, which is a phenomenon inherent to VHF plasma. Such a film forming test is repeatedly performed using the phase difference of the voltage of the power supplied to the first and second feeding points as a parameter.
Then, in the length direction of the first electrode 2, the relationship between the distance from the center point of the substrate 11 to the position of the maximum thickness of the sine film thickness distribution and the phase difference is grasped as data. For example, it is understood that the phase difference for setting a position that is one-eighth of the wavelength λ from the center point of the substrate 11 toward the first feeding point 27, that is, a position that is separated by λ / 8 is, for example, Δθ2. Is done.
Note that the method of grasping the relationship between the maximum position of the sinusoidal thickness distribution and the phase difference of the output voltage of the first variable-phase two-output transmitter 15a performed here is the measurement of the thickness distribution of the film. The method is not limited to the application method. For example, the spatial distribution of the emission intensity of the generated plasma in the electromagnetic wave propagation direction is measured with an optical sensor, and the relationship between the position of the maximum intensity and the phase difference is grasped. Also good.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

In the second preliminary film-forming step, voltage waves of pulse-modulated power supplied from the first and second feeding points 21 and 27 are oscillated from the same power source and propagate between the electrodes. That is, two electromagnetic waves having an electric field substantially in the same direction as the normal direction of the surface of the substrate 11 are generated between the first electrode 2 and the second electrode 4, and the two electromagnetic waves are from the directions facing each other. As they propagate and overlap, an interference phenomenon occurs. This will be described with reference to FIGS.
The direction substantially the same as the normal direction of the surface of the substrate 11 means a direction having a cosine value of 0.7 or more, that is, a direction within about 45 degrees from the normal line.
2 and 3, the distance in the direction from the first feeding point 21 to the second feeding point 27 is x, and the voltage wave propagating in the positive direction of x is W12 (x, t), in the negative direction of x. Assuming that a propagating voltage wave, that is, a voltage wave propagating from the second feeding point 27 to the first feeding point 21 is W22 (x, t), it is expressed as follows.
W12 (x, t) = V2 · sin (ωt + 2πx / λ)
W22 (x, t) = V2 · sin {ωt−2π (x−L0) / λ + Δθ}
Where V2 is the amplitude of the voltage wave, ω is the angular frequency of the voltage, λ is the wavelength of the voltage wave, t is the time, L0 is the interval between the first and second feed points, and Δθ is supplied from the first feed point 21. The phase difference between the voltage wave of the electric power and the voltage wave of the electric power supplied from the second feeding point 27 The voltage composite wave W2 (x, t) is expressed by the following equation.
W2 (x, t) = W12 (x, t) + W22 (x, t)
= 2 · V2cos {2π (x−L0 / 2) / λ−Δθ / 2} · sin {ωt + (πL0 / λ + Δθ / 2)
The synthetic wave W2 (x, t) is conceptually shown in FIG. In FIG. 4, when Δθ = 0, the intensity of the generated plasma is strong in the central portion (x = L0 / 2) between the feeding points, and decreases as the distance from the central portion increases. When Δθ> 0, the strong plasma portion moves to one feeding point side, and when Δθ <0, it moves to the other feeding point side.
Here, the voltage waves of the power supplied to the first and second feeding points 21 and 27 are referred to as W12 (x, t) and W22 (x, t), respectively. The combined wave of the two waves is called a second standing wave W2 (x, t).

By the way, the strength of the power between the pair of electrodes is proportional to the square of the amplitude value of the composite wave W2 (x, t) of the voltage. That is, the power intensity I2 (x, t) is
I2 (x, t) ∝cos ² {2π (x−L0 / 2) / λ−Δθ / 2}
It is expressed. This I2 (x, t) is conceptually shown in FIG.
FIG. 5 shows that it is difficult to obtain a uniform intensity plasma in the generation of the VHF plasma. The uniformity of the plasma between the pair of electrodes is, for example, in the range of −0.05 to + 0.05λ (ie, the distance in the power propagation direction when the intensity is in the range of 0.9 to 1.0 (that is, This indicates that the range in which the film thickness is uniform is limited to a length of 0.1λ).
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Now, in response to the results of the first and second preliminary film forming steps, the main film forming step is started. First, in FIG. 29, the substrate 11 is set on the second electrode 4 in advance, and the vacuum pump 10 (not shown) is operated to remove impurity gas and the like in the vacuum vessel 1, and then from the discharge gas supply pipe 8. While supplying SiH4 gas at, for example, 300 sccm and pressure of 0.5 Torr (66.5 Pa), the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C.
Next, high frequency power is supplied to the pair of electrodes 2 and 4 using a high frequency power supply device.
The frequency of the output of the high-frequency transmitter 70 is set to 60 MHz, for example, and the pulse widths Hw and periods of the electric power W11 (t) and W21 (t) supplied to the first feeding point 21 and the second feeding point are set. For example, T0 is set to Hw = 400 μsec and T0 = 1 msec, the pulse width Hw and period T0 of the power W12 (t) and W22 (t) are set to, for example, Hw = 400 μsec and T0 = 1 msec, and It is set so that it rises at a time that is half a cycle, ie, T0 / 2 delayed from the pulse rise time of the pulse modulation of W11 (t) and W21 (t). Then, the phase difference of the voltage of the electric power supplied to the first and second feeding points controlled by the first phase control system including the first phase difference detector 78 and the first phase shifter 76 is determined. First and second feeding points controlled by a second phase control system comprising the second phase difference detector 79 and the second phase shifter 77, set to Δθ1 grasped as data of the preliminary film forming step Is set to Δθ2 which is grasped as data of the second preliminary film-forming process.
The outputs of the first, second, third, and fourth amplifiers 16, 22, 29, and 34 are set to 200 W, for example. That is, at the first and second feeding points 21 and 27, a voltage wave W11 (x, t) with a power of 200 W, a voltage wave W21 (x, t) with a power of 200 W, a W12 (x, t) with a power of 200 W, and W22 (x, t) with power of 200 W is supplied.
Here, the values of the pulse width Hw and the period T0 set in the first preliminary film-forming process and the second preliminary film-forming process, for example, Hw = 400 μsec to 1 msec, T0 = 1 msec, etc. Some film-forming data can be compared by changing to 5 milliseconds or the like.

When four voltage waves are supplied between the pair of electrodes 2, 4, as described above, W 11 (x, t) and W 21 (x, t) interfere with each other and the first standing wave W 1 (x, t t), and W12 (x, t) and W22 (x, t) interfere to form a second standing wave W2 (x, t). However, W11 (x, t) does not interfere with W12 (x, t) and W22 (x, t) because they are temporally separated. Similarly, W21 (x, t) does not interfere with W12 (x, t) and W22 (x, t).
Accordingly, considering a general film formation time of several seconds or longer, which is significantly longer than the pulse modulation period T0, the distribution of the strength of power generated between the pair of electrodes 2 and 4 is the first standing wave. The intensity distribution I1 (x, t) of W1 (x, t) and the intensity distribution I2 (x, t) of the second standing wave W2 (x, t) are superimposed. This is conceptually shown in FIG.
Here, if the center point of the substrate is the origin of the x-axis and the direction from the origin toward the first feeding point 21 is a positive direction, the strength of the first standing wave W1 (x, t) Distribution I1 (x, t) is
I1 (x, t) ∝cos ² {2πx / 2 + 2π (λ / 8) / λ}
= Cos ² {2πx / 2 + π / 4}
The intensity distribution I2 (x, t) of the second standing wave W2 (x, t) is
I2 (x, t) ∝cos ² {2πx / 2-2π (λ / 8) / λ}
= Cos ² {2πx / 2−π / 4}
The distribution I (x, t) of the strength of power generated between the pair of electrodes 2 and 4 is
I (x, t)
= Cos ² {2πx / 2 + π / 4} + cos ² {2πx / 2−π / 4}
= 1

As a result, the high frequency used in the surface treatment apparatus for treating the surface of the substrate disposed in the vacuum vessel using the plasma generated using the power of the output of the high frequency power source whose oscillation frequency belongs to the VHF band or the UHF band. In the plasma generator, a first standing wave and a second standing wave are generated in which the positions of antinodes of the standing wave of the electromagnetic wave having an electric field substantially in the same direction as the normal direction of the surface of the substrate are different. In addition, the provision of means for superimposing the first and second standing waves makes it possible to control the distribution of power intensity between the electrodes, which is indispensable for plasma uniformity. .
Further, if the distance between the antinodes of the first and second standing waves is 0.25 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.25λ, a pair of electrodes The power intensity distribution I (x, t) generated between 2 and 4 has a constant value and does not depend on the position in the power propagation direction, and is uniform. This means that it is an epoch-making discovery in the sense that it is possible to provide an apparatus capable of realizing large-area and uniform plasma processing, which is an important issue in the application field of UHF plasma and UHF plasma. Yes.
The distance between the antinodes of the first and second standing waves is 0.22 to 0.28 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.22 to 0.2. If it is 28λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 20% or less.
The distance between the antinodes of the first and second standing waves is 0.238 to 0.263 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.238 to. In the case of H.263λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 10% or less.

In the above process, when SiH 4 gas is turned into plasma, radicals such as SiH 3, SiH 2, and SiH existing in the plasma diffuse due to a diffusion phenomenon and are adsorbed on the surface of the substrate 11, thereby depositing an a-Si film. However, since the power distribution between the pair of electrodes 2 and 4 is uniform in time average as described above, the deposited film becomes uniform.
This indicates that the apparatus and method of the present invention can form a uniform film thickness distribution even when a substrate having a size exceeding one half of the wavelength λ is targeted. That is, even when a substrate having a size exceeding one-half of the wavelength λ, which is impossible with the conventional VHF plasma surface treatment apparatus and method, is targeted, the present invention can realize a uniform film thickness distribution. It means that.
Therefore, the above is an epoch-making discovery in the application field of VHF plasma, and its practical value is extremely large.
It is a well-known technique that microcrystalline Si, thin-film polycrystalline Si, or the like can be formed by optimizing the flow ratio, pressure, and power of SiH4 and H2 in the film forming conditions.
In addition, it is a known technique that can be applied to etching by using NF3, SF6, CF4, CHF3, C4F4, or the like as a discharge gas.

In this embodiment, since the first and second electrodes 2 and 4 are about 1400 mm × 200 mm in size, the substrate size is limited to about 1200 mm × 200 mm. However, if the width of the first electrode 2 and the number of feeding points are increased. Of course, the width of the substrate size can be expanded.
Further, in the present embodiment, only the case where the power supply frequency is 60 MHz has been described. However, the constituent members of the high-frequency power supply apparatus have no problem in power transmission and control at a frequency of 10 MHz to 300 MHz (VHF band). Is natural. Even in the frequency range of 300 MHz to 3 GHz (UHF band), although there is a transmission loss, it can be put to practical use.
Further, in the present embodiment, only the case where the shape of the first electrode 2 is rectangular has been described, but the shape is other than a rectangle, for example, a rod-shaped conductor formed in a U shape and a W shape, It is easy to arrange the first and second feeding points 21 and 27 at both ends of the electrode.
Further, in application to the case where the shape of the substrate is cylindrical, it can be easily considered that the electrode shape is cylindrical and the first and second feeding points 21 and 27 are arranged on the end face of the cylindrical electrode.

In the manufacture of a-Si solar cells, thin film transistors, and photosensitive drums, there is no problem in performance as long as the film thickness distribution is within ± 10%.
According to the above embodiment, even when a power supply frequency of 60 MHz is used, the distribution of power intensity I (x, t) between the pair of electrodes 2 and 4 that is impossible with the conventional apparatus and method is uniform. Is possible. In other words, the film thickness distribution can be within ± 10%. This means that the industrial value related to productivity improvement and cost reduction in the manufacturing field of a-Si solar cells, thin film transistors, and photosensitive drums is remarkably large.

Here, the pair of electrodes 2 and 4 having the structure shown in FIG. 2 which is one of the components of the apparatus of the present embodiment is replaced with the pair of electrodes 2 and 4 shown in FIG. It should be noted that the same plasma treatment as in this embodiment can be performed by using a plasma surface treatment apparatus instead of the pair of electrodes composed of 2 and the plate electrode 4.
In this case, as compared with the plasma generated by a pair of electrodes composed of the rod-shaped electrode 2 and the plate electrode 4 in FIG. 2, there is an advantage that it is possible to easily generate plasma having a spread in a direction perpendicular to the propagation direction of electromagnetic waves. is there.

Further, the pair of electrodes 2 and 4 having the structure shown in FIG. 2 which is one of the components of the apparatus of this embodiment is replaced with the pair of electrodes 2 and 4 having the structure shown in FIG. It should be noted that the same plasma treatment as in this embodiment can be performed by using a plasma surface treatment apparatus instead of the pair of electrodes composed of the electrode 2 and the plate electrode 4. Note that the line segment connecting the first power supply point 21a and the second power supply point 27a shown in FIG. 8 and the line segment connecting the third power supply point 21b and the fourth power supply point 27b need to be parallel. It is natural.
In this case, as compared with the plasma generated by the pair of electrodes composed of the rod-shaped electrode 2 and the plate electrode 4 shown in FIG. 2, it is possible to easily generate plasma that spreads in a direction perpendicular to the propagation direction of the electromagnetic wave. In addition to the above, there is an advantage that it is possible to distribute the power supplied to the feeding point. That is, it has a feature that it can be applied to plasma processing applications that require high power.

Further, a plasma surface treatment apparatus is used in which the pair of electrodes 2 and 4 having the structure shown in FIG. 2, which is one of the components of the apparatus of this embodiment, is replaced with the rod-like electrodes 2a and 2b having the structure shown in FIG. Note that the same plasma treatment as in this embodiment can be performed.
The first rod-like electrode 2a and the second rod-like electrode 2b shown in FIG. 9 need to be installed in parallel.
In this case, there is an advantage that it is possible to disperse the electric power supplied to the feeding point as compared with the plasma generated by the pair of electrodes composed of the rod-like electrode 2 and the plate electrode 4 shown in FIG. That is, it has a feature that it can be applied to plasma processing applications that require high power.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the whole high frequency plasma generator concerning Example 1, and the plasma surface treatment apparatus (plasma CVD apparatus) comprised by this high frequency plasma generator. Explanatory drawing which shows the basic type of a structure which concerns on a pair of electrode which is one of the structural members of the plasma surface treatment apparatus shown in FIG. 1, and its electric power feeding part. Explanatory drawing which shows the electromagnetic waves which propagate between a pair of electrodes. Explanatory drawing which shows the position of the antinode of the standing wave of the voltage generated between a pair of electrodes. Explanatory drawing which shows the intensity | strength (value of the square of an amplitude) of the standing wave generated between a pair of electrodes. Explanatory drawing which shows the intensity | strength of two standing waves generated between a pair of electrodes. Explanatory drawing which shows the 1st application type | mold of the structure regarding a pair of electrode which is one of the structural members of the plasma surface treatment apparatus shown in FIG. 1, and its electric power feeding part. Explanatory drawing which shows the 2nd application type | mold of the structure concerning a pair of electrode which is one of the structural members of the plasma surface treatment apparatus shown in FIG. 1, and its electric power feeding part. Explanatory drawing which shows the 3rd application type of a structure regarding a pair of electrode which is one of the structural members of the plasma surface treatment apparatus shown in FIG. 1, and its electric power feeding part. Schematic which shows the whole high frequency plasma generator concerning Example 2, and the plasma surface treatment apparatus (plasma CVD apparatus) comprised by this high frequency plasma generator. Explanatory drawing which shows the typical example of the pulse-modulated output output from the 1st and 2nd pulse modulation system variable phase 2 output transmitter. Explanatory drawing which shows the typical example of the pulse-modulated sine wave signal output from the 1st and 2nd pulse modulation system phase variable 2 output transmitter. Schematic which shows the whole high frequency plasma generator concerning Example 3, and the plasma surface treatment apparatus (plasma CVD apparatus) comprised by this high frequency plasma generator. FIG. 14 is a wiring diagram of a first power supply system used in the apparatus shown in FIG. 13. FIG. 14 is a wiring diagram of a second power supply system used in the apparatus shown in FIG. 13. Explanatory drawing which shows the structure regarding a pair of electrode which consists of a rectangular conductor board used for the apparatus shown in FIG. 13, and its electric power feeding part. Schematic which shows the whole high frequency plasma generator concerning Example 4, and the plasma surface treatment apparatus (plasma CVD apparatus) comprised by this high frequency plasma generator. FIG. 18 is a cross-sectional view of the inside of the vacuum vessel of the plasma surface treatment apparatus shown in FIG. 17. Explanatory drawing which shows the 1st applied type of the structure regarding a pair of electrode used as a structural member of the apparatus of FIG. 17 illustration, and its electric power feeding part. Explanatory drawing which shows the 2nd applied type of a structure regarding a pair of electrode used as a structural member of the apparatus of FIG. 17 illustration, and its electric power feeding part. Explanatory drawing which shows the 3rd applied type of a structure regarding a pair of electrode used as a structural member of the apparatus of FIG. 17 illustration, and its electric power feeding part. Schematic which shows the whole plasma generating apparatus concerning Example 5, and the plasma surface processing apparatus (plasma CVD apparatus) comprised by this plasma generating apparatus. Explanatory drawing which shows the electric power supply system wiring diagram of the plasma surface treatment apparatus shown in FIG. Schematic which shows the whole high frequency plasma generator concerning Example 6, and the plasma surface treatment apparatus (plasma CVD apparatus) comprised by this high frequency plasma generator. Schematic which shows the whole high frequency plasma generator concerning Example 7, and the plasma surface treatment apparatus (plasma CVD apparatus) comprised by this high frequency plasma generator. Schematic which shows the whole high frequency plasma generator concerning Example 8, and the plasma surface treatment apparatus (plasma CVD apparatus) comprised by this high frequency plasma generator. FIG. 27 is an explanatory diagram showing an applied type of a configuration related to a pair of electrodes used as components of the apparatus shown in FIG. Schematic which shows the whole high frequency plasma generator concerning Example 9, and the plasma surface treatment apparatus (plasma CVD apparatus) comprised by this high frequency plasma generator. Schematic which shows the whole high frequency plasma generator concerning Example 10, and the plasma surface treatment apparatus (plasma CVD apparatus) comprised by this high frequency plasma generator.

Explanation of symbols

1. . . Vacuum vessel,
2. . . A first electrode,
3. . . Substrate heater (not shown),
4). . . A second electrode,
5. . . Insulator support material,
6). . . Gas mixing box,
7). . . Rectifying hole,
8). . . Discharge gas supply pipe,
9. . . Exhaust pipe,
10. . . Vacuum pump not shown,
11. . . substrate,
12 . . Gate valve not shown,
15. . . A first pulse modulation phase variable two-output transmitter;
16. . . A first power amplifier;
17. . . A first impedance matcher;
18. . . A first current introduction terminal;
19. . . First coaxial coaxial cable,
20. . . The core wire of the first vacuum coaxial cable,
21. . . A first feeding point,
22. . . A second power amplifier,
23. . . A second impedance matcher;
24. . . A second current introduction terminal,
25. . . A second coaxial coaxial cable,
26. . . The core wire of the second vacuum coaxial cable,
27. . . A second feeding point,
100. . . Sync signal transmission cable,
28. . . A second pulse modulation type phase variable two-output transmitter;
29. . . A third power amplifier,
30. . . A third impedance matcher;
31. . . A third current introduction terminal;
32. . . A third coaxial cable for vacuum,
33. . . A core wire of a third vacuum coaxial cable;
34. . . A fourth power amplifier,
35. . . A fourth impedance matcher;
36. . . A fourth current introduction terminal;
37. . . A fourth coaxial cable for vacuum,
38. . . A core wire of a fourth coaxial cable for vacuum.

Claims (25)

  In a high-frequency plasma generator used in a surface processing apparatus for processing the surface of a substrate disposed in a vacuum vessel using plasma generated using power output from a high-frequency power source whose oscillation frequency belongs to the VHF band or UHF band A high-frequency plasma generator comprising means for generating a plurality of standing waves having different antinode positions of electromagnetic standing waves between electrodes and superimposing them.   2. The high-frequency plasma generator according to claim 1, further comprising means for generating a plurality of standing waves having different antinode positions of the standing wave of electromagnetic waves and superposing them, and A high-frequency plasma generator comprising means for controlling the position of the belly.   3. The high-frequency plasma generator according to claim 2, wherein the first standing wave and the second standing wave are generated at different positions of antinodes of the standing wave of the electromagnetic wave, and the first and second standing waves are generated. A high-frequency plasma generator comprising means for superimposing standing waves.   4. The high-frequency plasma generator according to claim 2, wherein a plurality of standing waves are respectively generated in a plurality of directions in a plane parallel to the electrode, and the plurality of standing waves are generated. A high frequency plasma generator characterized by comprising means for superimposing.   5. The high-frequency plasma generator according to claim 4, wherein the first standing wave and the second standing wave are generated in one of two directions orthogonal to each other in a plane parallel to the electrode, and the other Characterized in that it comprises means for generating a third standing wave and a fourth standing wave in the direction of and superimposing the first, second, third and fourth standing waves. High frequency plasma generator.   The means for generating the first standing wave and the second standing wave and for superimposing the first and second standing waves from the first and second electrodes having a plurality of feeding points A first high-frequency power source having a pair of electrodes and two output terminals and capable of arbitrarily setting a phase difference between voltages of the outputs of the two output terminals, and two outputs of the first high-frequency power source First and second impedance matching units connected to the terminals one by one, independent of the first high-frequency power source, and having two output terminals, and the output voltage of the two output terminals A second high-frequency power source capable of arbitrarily setting the phase difference of the second high-frequency power source, and third and fourth impedance matching units respectively connected to two output terminals of the second high-frequency power source, The first and third impedance matchings at a first feeding point disposed on the first electrode The second and fourth impedance matchers are connected to a second feed point that is connected to the first feed point and is located at a position that is a point opposite to the first feed point in the propagation of electromagnetic waves. The high frequency plasma generator according to claim 3, wherein the output terminal is connected.   The means for generating the first standing wave and the second standing wave and for superimposing the first and second standing waves from the first and second electrodes having a plurality of feeding points A first high-frequency power source having a pair of electrodes and two output terminals and capable of arbitrarily setting a phase difference between voltages of the outputs of the two output terminals, and two outputs of the first high-frequency power source First and second impedance matching units connected to the terminals one by one, independent of the first high-frequency power source, and having two output terminals, and the output voltage of the two output terminals A second high-frequency power source capable of arbitrarily setting the phase difference of the second high-frequency power source, and third and fourth impedance matching units respectively connected to two output terminals of the second high-frequency power source, The output of the first impedance matching unit is connected to a first feeding point arranged on the first electrode. The output terminal of the second impedance matching device is connected to the second feeding point that is connected to the second feeding point that is connected to the first feeding point and is the opposite point in the propagation of electromagnetic waves. And each of the third and fourth feed points arranged at a position parallel to the line segment connecting the first feed point and the second feed point, respectively. 4. The high-frequency plasma generator according to claim 3, wherein the output terminal of the fourth impedance matching unit is connected.   The means for generating the first standing wave and the second standing wave and for superimposing the first and second standing waves from the first and second electrodes having a plurality of feeding points A pair of electrodes, a first high-frequency power source capable of arbitrary pulse modulation, having two output terminals, and capable of arbitrarily setting the phase difference of the output voltage of the two output terminals, The first and second impedance matching units connected to the two output terminals of the first high-frequency power source one by one, and arbitrary pulse modulation synchronized with the pulse modulation signal of the first high-frequency power source is possible. And there are two output terminals, one for each of the two output terminals of the second high-frequency power supply and the second high-frequency power supply that can arbitrarily set the phase difference of the output voltage of the two output terminals. And third and fourth impedance matchers connected to each other, A relationship in which the output terminals of the first and third impedance matching devices are connected to the first feeding point arranged at the pole, and the opposing point in the propagation of electromagnetic waves with respect to the first feeding point 4. The high-frequency plasma generator according to claim 3, wherein the output terminals of the second and fourth impedance matching units are connected to a second feeding point arranged at a position at the position.   The means for generating the first standing wave and the second standing wave and for superimposing the first and second standing waves from the first and second electrodes having a plurality of feeding points A pair of electrodes, a first high-frequency power source capable of arbitrary pulse modulation, having two output terminals, and capable of arbitrarily setting the phase difference of the output voltage of the two output terminals, The first and second impedance matching units connected to the two output terminals of the first high-frequency power source one by one, and arbitrary pulse modulation synchronized with the pulse modulation signal of the first high-frequency power source is possible. And there are two output terminals, one for each of the two output terminals of the second high-frequency power supply and the second high-frequency power supply that can arbitrarily set the phase difference of the output voltage of the two output terminals. And third and fourth impedance matchers connected to each other, The output terminal of the first impedance matching device is connected to the first feeding point arranged at the pole, and the first feeding point is arranged at a position that is the opposite point in the propagation of electromagnetic waves with respect to the first feeding point. The output terminal of the second impedance matching device is connected to the second feeding point that has been made, and is arranged at a position parallel to the line segment connecting the first feeding point and the second feeding point 4. The high-frequency plasma according to claim 3, wherein the output terminals of the third and fourth impedance matching units are connected to the third and fourth feeding points, respectively, one by one. Generator.   The means for generating the first standing wave and the second standing wave and for superimposing the first and second standing waves from the first and second electrodes having a plurality of feeding points A pair of electrodes, a high-frequency power source capable of arbitrary pulse modulation, having four output terminals and capable of arbitrarily setting the phase of the output voltage of each of the four output terminals, and four of the high-frequency power sources A first, a second, a third and a fourth impedance matching unit connected to each one of the output terminals, the first feeding point disposed on the first electrode being connected to the first feeding point; To the second feeding point disposed at a position where the output terminals of the first and third impedance matching units are connected and are in a relationship that is an opposing point on the propagation of electromagnetic waves with respect to the first feeding point, A configuration in which the output terminals of the second and fourth impedance matching units are connected. High frequency plasma generating apparatus according to claim 3, characterized in that.   The means for generating the first standing wave and the second standing wave and for superimposing the first and second standing waves from the first and second electrodes having a plurality of feeding points A pair of electrodes, a high-frequency power source capable of arbitrary pulse modulation, having four output terminals and capable of arbitrarily setting the phase of the output voltage of each of the four output terminals, and four of the high-frequency power sources The first, second, third, and fourth impedance matching units connected to each of the output terminals one by one, and the first feeding point disposed on the first electrode is connected to the first feeding point. The output terminal of the impedance matching device is connected, and the second impedance matching is connected to the second feeding point disposed at a position that is a point opposite to the first feeding point in the propagation of electromagnetic waves. And the first feeding point and the second feeding point. It has a configuration in which the output terminals of the third and fourth impedance matching devices are connected to the third and fourth feeding points arranged at positions parallel to the connecting line segments, respectively. The high-frequency plasma generator according to claim 3.   The high frequency plasma according to any one of claims 8 to 11, wherein the duty ratio of the pulse modulation of the output of the high frequency power source, that is, the ratio Hw / T0 of the pulse width Hw and the period T0 is 50% or less. Generator.   The distance between the antinode of the first standing wave and the antinode of the second standing wave is 0.22 to 0.22 of the wavelength λ of the electromagnetic wave propagating through the generated plasma between the pair of electrodes. 13. A means according to any one of claims 2 to 12, characterized in that it has means for setting it to be 0.28 times, preferably 0.25 times, ie 0.22 to 0.28λ, preferably λ / 4. The high frequency plasma generator described in 1.   The second electrode has a flat plate shape, and the first electrode has a square or circular flat plate structure arranged so as to be included in a plane parallel to the second electrode. The high-frequency plasma generator according to claim 1, wherein:   The second electrode has a flat plate shape, and the first electrode is a rod-shaped, U-shaped, W-shaped or a bar-shaped conductor disposed in a plane parallel to the second electrode. The high-frequency plasma generator according to claim 1, wherein the high-frequency plasma generator has a spiral structure.   The second electrode has a cylindrical shape, and the first electrode is a rod-shaped or U-shaped rod made of a rod-shaped conductor disposed in a cylindrical surface surrounding the second electrode in a sheath shape. The high-frequency plasma generator according to claim 1, wherein the high-frequency plasma generator has a W-shaped structure or a coil-shaped structure.   The first and second electrodes are plate-like conductors having a plurality of openings, and the substrate is arranged outside the pair of electrodes. 14. The high-frequency plasma generator according to any one of items 13.   18. A plasma surface processing apparatus for processing a surface of a substrate disposed in a vacuum vessel using plasma generated using power of an output of a high frequency power source whose oscillation frequency belongs to a VHF band or a UHF band. A plasma surface treatment apparatus comprising the high-frequency plasma generation apparatus according to any one of the above.   18. A plasma surface treatment method for treating a surface of a substrate disposed in a vacuum vessel by using plasma generated using power of an output of a high frequency power source whose oscillation frequency belongs to a VHF band or a UHF band. A plasma surface treatment method, wherein the surface treatment of the substrate is performed using the high-frequency plasma generator according to any one of the above.   8. A plasma surface treatment method for treating a surface of a substrate disposed in a vacuum vessel by using plasma generated by using power of an output of a high-frequency power source whose oscillation frequency belongs to a VHF band or a UHF band. Using the high-frequency plasma generation device according to any one of the above, the first and second electrodes disposed at at least two points in a relationship of opposing points in the propagation of electromagnetic waves on the surface of the first electrode The output terminal of the first and third impedance matching units is connected to one of the feeding points, and the output terminal of the second and fourth impedance matching units is connected to the other feeding point. , The phase difference of the voltage of the power output from the output terminals of the first and second impedance matchers and the output from the output terminals of the third and fourth impedance matchers The phase difference between the two standing wave antinodes, that is, between the position of the antinode of the first standing wave and the position of the antinode of the second standing wave. Of 0.2 to 0.28 times, preferably 0.25 times, ie 0.22 to 0.28λ, preferably λ / of the wavelength λ of the electromagnetic wave propagating through the generated plasma between the pair of electrodes. 4. A plasma surface treatment method, wherein the surface treatment of the substrate is performed by setting to 4.   10. A plasma surface treatment method for treating a surface of a substrate disposed in a vacuum vessel by using plasma generated using power of an output of a high frequency power source whose oscillation frequency belongs to a VHF band or a UHF band. Using the high-frequency plasma generation device according to any one of the above, the first and second electrodes disposed at at least two points in a relationship of opposing points in the propagation of electromagnetic waves on the surface of the first electrode The output terminal of the first and third impedance matching units is connected to one of the feeding points, and the output terminal of the second and fourth impedance matching units is connected to the other feeding point. At the same time, the power output from the first and second output terminals of the first high-frequency power supply is pulse-modulated with a pulse width Hw and a pulse period T0, and the first high-frequency power supply And pulse modulation in such a manner that the power output from the second output terminal rises at a half cycle, ie, a time delayed by T0 / 2 from the rise time of the pal-modulated power output from the output terminal of the first high-frequency power supply. By doing so, pulse-modulated power output from the first and second output terminals of the first high-frequency power supply and pulse modulation output from the first and second output terminals of the second high-frequency power supply The two powers that are output from the first and second output terminals of the first high-frequency power source are separated between the pair of electrodes by separating the supply time zones of the generated power to the first and second feeding points And the time zone of occurrence of the second standing wave formed by the two electric powers output from the first and second output terminals of the second high-frequency power source are different from each other. And the first and second impedance adjustments The phase difference between the voltage of the power output from the output terminal of the voltage detector and the phase difference between the voltage of the power output from the output terminals of the third and fourth impedance matching devices are controlled, and the two standing waves The distance between the antinode positions, that is, the distance between the antinode positions of the first standing wave and the antinode position of the second standing wave is the wavelength of the electromagnetic wave propagating inside the generated plasma between the pair of electrodes. The surface treatment of the substrate is performed by setting 0.22 to 0.28 times λ, preferably 0.25 times, that is, 0.22 to 0.28λ, preferably λ / 4. Plasma surface treatment method.   12. A plasma surface treatment method for treating a surface of a substrate disposed in a vacuum vessel by using plasma generated using power output from a high-frequency power source whose oscillation frequency belongs to a VHF band or a UHF band. Using the high-frequency plasma generation device according to any one of the above, the first and second electrodes disposed at at least two points in a relationship of opposing points in the propagation of electromagnetic waves on the surface of the first electrode The output terminal of the first and third impedance matching units is connected to one of the feeding points, and the output terminal of the second and fourth impedance matching units is connected to the other feeding point. In addition, the power output from the first and second output terminals of the high-frequency power source is pulse-modulated with a pulse width Hw and a pulse period T0, and the third and fourth of the high-frequency power source The high-frequency power supply is pulse-modulated in such a manner that the power output from the output terminal rises at a half cycle, ie, a time delayed by T0 / 2 from the rise time of the pal-modulated power output from the first output terminal. The first and second feed points for the pulse-modulated power output from the first and second output terminals of the power supply and the pulse-modulated power output from the third and fourth output terminals of the high-frequency power supply The first standing wave formed by two electric powers output from the first and second output terminals of the high-frequency power source between the pair of electrodes and the first of the high-frequency power source The second standing wave generation time zone formed by the two electric powers output from the third and fourth output terminals is differentiated and output from the output terminals of the first and second impedance matching devices. Power voltage phase And the phase difference of the voltage of the power output from the output terminals of the third and fourth impedance matchers, and the distance between the antinodes of the two standing waves, that is, the first standing wave The distance between the position of the antinode and the position of the antinode of the second standing wave is 0.22 to 0.28 times the wavelength λ of the electromagnetic wave propagating through the generated plasma between the pair of electrodes, preferably 0. The plasma surface treatment method is characterized in that the surface treatment of the substrate is performed by setting to 25 times, that is, 0.22 to 0.28λ, preferably λ / 4.   The step of grasping the position of the antinode of the first standing wave, the step of grasping the position of the antinode of the second standing wave, the position of the first antinode and the antinode of the second standing wave The distance between the electrodes is 0.22 to 0.28 times, preferably 0.25 times, ie 0.22 to 0.28λ, preferably 0.25 to 0.28 times the wavelength λ of the electromagnetic wave propagating through the generated plasma between the pair of electrodes. The plasma surface treatment method according to any one of claims 20 to 22, further comprising a step of performing a plasma surface treatment of a substrate by setting to λ / 4.   An amorphous Si-based material, a microcrystalline Si-based material, a polycrystalline Si-based material, a crystalline Si-based material, an oxide, a metal, an organometallic compound, an organosilicon compound, or an organic compound is formed on the surface of the substrate. The plasma surface treatment method according to any one of claims 20 to 23, wherein the plasma surface treatment method is performed. Any material of amorphous Si-based material, microcrystalline Si-based material, polycrystalline Si-based material, crystalline Si-based material, oxide, metal, organometallic compound, organosilicon compound, and organic compound fixed on the surface of the substrate The plasma surface treatment method according to any one of claims 20 to 23, wherein the etching process is performed.

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