JP3575011B1 - Plasma surface treatment apparatus and plasma surface treatment method - Google Patents

Abstract

[PROBLEMS] A VHF band (30 to 300 MHz) plasma is uniformly generated with good reproducibility between a pair of electrodes in a vacuum vessel even on a 1mx1m class large area substrate, and a uniform plasma surface treatment on the substrate is possible. To provide a surface treatment apparatus and a surface treatment method.
A surface treatment apparatus and method for treating the surface of a substrate (13) disposed on one of a pair of electrodes (2) and (4) in a vacuum vessel (1) using a plasma, the coaxial cable being connected to the pair of electrodes (2) and (4). 16c, a balance-unbalance conversion device 19 is inserted between the matching device 17 and the pair of electrodes 2 and 4, and a standing wave detection device 61 is inserted between the pair of electrodes 2 and 4. It is characterized in that a reactance adjusting device 71 is added in parallel.
[Selection diagram] FIG.

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface treatment apparatus and a surface treatment method for performing a predetermined treatment on the surface of a substrate using plasma. The present invention particularly relates to a surface treatment apparatus and a surface treatment method using reactive plasma that generates plasma by glow discharge of a discharge gas generated by high-frequency power having a frequency of 30 MHz to 300 MHz.
[0002]
[Prior art]
Manufacturing various electronic devices by performing various processes on the surface of the substrate using reactive plasma includes LSI (Large Scale Integrated Circuit), LCD (Liquid Crystal Display), amorphous Si solar cell, thin film polycrystalline Si system It has already been put to practical use in the fields of solar cells, photoconductors for copiers, and various information recording devices. Practical application is also progressing in the field of manufacturing ultra-hard films such as diamond thin films and cubic boron nitride (C-BN).
[0003]
Although the above technical fields cover a wide variety of fields, such as thin film formation, etching, surface modification, and coating, all of them utilize the chemical and physical actions of reactive plasma. The apparatus and method relating to the generation of the reactive plasma are roughly classified into two typical techniques.
[0004]
A first representative technique is described in, for example, Patent Literature 1 and Non-Patent Literature 1, and is characterized in that two parallel plate electrodes are used as a pair for plasma generation. A second representative technique is described in, for example, Patent Documents 2 and 3, and is characterized in that a ladder electrode and a plate electrode are used as a pair for plasma generation. Hereinafter, two examples will be described on behalf of the prior art.
[0005]
(Conventional example 1)
First, an apparatus and a method described in Patent Document 1 will be described with reference to FIGS. 11 and 12 as a first representative example of the related art. FIG. 11 is a configuration diagram of a plasma surface treatment apparatus according to a first conventional typical technique, and FIG. 12 is an explanatory diagram showing power supply points to electrodes according to a first conventional typical technique. As shown in FIG. 11, a first representative example of the related art includes a vacuum vessel 101, a ground electrode 104 on which a substrate 113 is provided, an ungrounded electrode 102 disposed facing the ground electrode 104, and a space between these electrodes. A power supply system for supplying high-frequency power, a discharge gas supply system, and an exhaust system are provided.
[0006]
The ground electrode 104 includes a substrate heater 103 and sets the temperature of the substrate 113 to a predetermined value. The non-grounded electrode 104 is specifically a rectangular plate (area of about 500 mm × 500 mm to about 1,000 mm × 1,000 mm), and is made of stainless steel.
[0007]
On the other hand, the non-grounded electrode 102 is attached to the upper part of the vacuum vessel 101 via an insulator 106. The interior of the non-grounded electrode 102 is hollow, and a large number of gas ejection holes 102b having a diameter of about 0.5 mm are arranged at a hole interval of 10 to 15 mm on a surface 102a in contact with the space 192 where plasma is generated.
[0008]
An opening 102c for a discharge gas is arranged on the upper surface of the non-ground electrode 102. A discharge gas introduction pipe 109 is connected to the opening 102c via a connection member 194 (material is ceramics), and for example, silane gas (SiH4) is supplied from a source gas supply source (not shown) via a valve 193. The gas in the vacuum vessel 101 is discharged from a vacuum pump 112 through an exhaust pipe 111. The substrate 113 is placed on the ground electrode 104 with the gate valve 195 opened, and is heated to a predetermined temperature by the substrate heater 103 and the substrate heater power supply 191.
[0009]
At the power supply points 114a and 114b of the ungrounded electrode 102, an output of a high-frequency power supply 115 for generating a predetermined high-frequency power is provided with a power divider 190 for distributing the output to a plurality of first and second matching circuits 117a and 117a. , 117b and the first, second, third, and fourth coaxial cables 116a, 116b, 116c, 116d. As shown in FIG. 12, the core wire 123 of the coaxial cable 116d is connected to the power supply point 114b, and the vicinity thereof is insulated by the insulating ring 121. Then, the end of the outer conductor of the coaxial cable 116d is connected to the vacuum vessel 101 using the ground conductor 196. Reference numerals 102 and 106 in FIG. 12 are an ungrounded electrode and an insulator, respectively.
[0010]
When plasma is generated, the output of the high-frequency power supply 15 is set to a predetermined value, and the first and second matching devices 117a are observed while looking at a detector (monitor) of a traveling wave / reflected wave attached to the high-frequency power supply (not shown). , 117b are sequentially adjusted to set a state where the reflected wave is approximately 1 to 10%. As a result, approximately 90% to 99% of the output of the high-frequency power supply is supplied from the matching units 117a and 117b to the downstream side.
[0011]
Next, a case where an amorphous Si (a-Si) film is formed using the apparatus shown in FIGS. 11 and 12 will be described. The gate valve 195 is opened, the substrate 113 is placed on the ground electrode 104, and the gate valve 195 is closed again. The vacuum pump 112 is driven to evacuate the pressure in the vacuum vessel 101 to about 1E-7 Torr (1.33E-5 Pa). The temperature of the substrate 113 is set to a predetermined temperature using the substrate heater 103 and the substrate heater power supply 191. A predetermined amount of, for example, silane gas is supplied through the discharge gas introducing pipe 109, the inside of the vacuum vessel 101 is maintained at 0.05 to 0.5 Torr (6.65 to 66.5 Pa), and a pair of electrodes is formed using the power supply system. Power is supplied between 102 and 104. As a result, glow discharge plasma is generated between the non-ground electrode 102 and the ground electrode 104. When the silane gas is converted into plasma, radicals such as SiH3, SiH2, and SiH existing therein are diffused by a diffusion phenomenon, and are adsorbed and deposited on the surface of the substrate 113. As a result, an amorphous Si film is formed.
[0012]
In addition, by adjusting the mixing ratio of the discharge gas, for example, the flow ratio of SiH4 and H2, the pressure, the substrate temperature, and the plasma generation power as film forming conditions, not only a-Si but also microcrystalline Si and polycrystalline It is known that a Si film can be manufactured.
[0013]
It is known that the etching of the substrate surface can be performed by using an etching gas such as SF6, SiCl4, CF4 and NF3 as a discharge gas.
[0014]
(Conventional example 2)
Next, as a second conventional example of the related art, the related art described in Patent Literature 2 and Patent Literature 3 will be described with reference to FIGS. FIG. 13 is a conceptual diagram of a surface treatment apparatus according to the second related art, FIG. 14 is a block diagram of a power supply system used to supply power to a pair of electrodes according to the apparatus shown in FIG. 13, and FIG. FIG. 16 is an explanatory diagram showing a power supply point to an electrode related to the device, FIG. 16 is an explanatory diagram of a voltage wave, and FIG. 17 is an explanatory diagram of a composite wave of a voltage. As shown in FIGS. 13 and 14, a plasma surface treatment apparatus according to the second prior art includes a vacuum vessel 201, a ground electrode 204 on which a substrate 213 is installed, and a ladder disposed facing the ground electrode 204. A non-grounded electrode 202 (referred to as a ladder electrode) having a mold structure, a power supply system for supplying high-frequency power between these electrodes, a discharge gas supply system, and an exhaust system are provided.
[0015]
A vacuum pump 212 is connected to the vacuum vessel 201 via an exhaust pipe 211 for exhausting a gas such as a reaction gas in the vacuum vessel 201. Then, an earth shield 208 is provided. The earth shield 208 is used in combination with the exhaust pipe 211 to discharge the reaction gas and other products introduced from the reaction gas introduction pipes 209a and 209b through the exhaust pipe 211. When the vacuum pump 212 is operated, the vacuum pump 212 is evacuated to a pressure of about 1E-6 Torr (1.33E-4Pa). When, for example, silane gas is supplied as a reaction gas from the reaction gas introduction pipes 209a and 209b, the silane gas flows uniformly between the ladder electrode 202 and the ground electrode 204 from a number of gas ejection holes (not shown).
[0016]
The substrate 213 is held by a ground electrode 204 and is heated to a predetermined temperature by a built-in heater 203 (not shown). Glass having a size of 460 mm × 460 mm and a thickness of about 1 mm is used for the substrate. The ladder electrode 202 is manufactured by assembling round bar members each having a size of, for example, about 520 mm × 520 mm and a diameter of about 6 mm at regular intervals in a ladder shape. As shown in FIG. 14 and FIG. 15, power is supplied to the electrode 202 at four power supply points 214a to 214d and connected to the coaxial cables 216a, 216b, 216c and 216d.
[0017]
As shown in FIGS. 13 and 14, the power supply system includes a high-frequency oscillator 232, a signal distributor 233, a phase shifter (phase shifter) 234, a pair of power amplifiers 236a and 236b, a pair of matching devices 217a and 217b, and a pair of Power distributors 240a and 240b and a computer 235. The phase of one voltage of the two outputs of the signal distributor 233 is temporally changed in a range of ± 180 degrees by the phase shifter 234 driven and controlled by the computer 235. The signal having the phase change is power-amplified by the second power amplifier 234b, and supplied to the feeding points 214c and 214d via the second matching unit 217b and the second power distributor 236b. The other output is supplied to feed points 214a and 214b via a first power amplifier 236a, a first matching device 217a, and a first power distributor 240a.
[0018]
Specifically, as shown in FIG. 15, a core wire (inner conductor) 223 of a coaxial cable installed through the ground shield 208 is connected to a feed point 214a of the ladder electrode 202, for example. The core wire 223 is surrounded by a discharge prevention insulating ring 237. The outer conductor of the coaxial cable is connected to the earth shield 208 by a mounting ring 239, and the end is shaped by a coupling 241.
[0019]
When plasma is generated, the first and second matching devices 217a and 217b are sequentially adjusted while looking at a detector (monitor) (not shown) for traveling waves and reflected waves attached to the power amplifiers 236a and 236b, and the reflected waves are adjusted. Is set to a state of about 1 to 10%. As a result, approximately 90% to 99% of the output of the power amplifiers 236a and 236b is supplied to the downstream side from the matching units 217a and 217b, respectively.
[0020]
Next, a case where, for example, a microcrystalline Si film is manufactured using the apparatus shown in FIGS. 13 and 14 will be described. A substrate 213, for example, a glass of 460 mm × 460 mm is set on the ground electrode 204 by a gate valve (not shown), and the gate valve is closed. Subsequently, as in the first conventional example, the vacuum pump 212 is driven to evacuate to a predetermined degree of vacuum. The temperature of the substrate 213 is set to 200 ° C., and the pressure is set to 0.15 Torr (20 Pa) while supplying silane gas at 500 sccm and hydrogen gas at 3,500 sccm.
[0021]
Then, the frequency of the high-frequency oscillator 232 is set to, for example, 60 MHz. The phase of one output signal (sine wave) of the signal distributor 233 is temporally modulated by the phase shifter 234 into a triangular waveform. In this case, the electric field between the ladder electrode 202 and the ground electrode 204 changes correspondingly because the phase difference of the voltage of the power supplied to the feeding points 214a, 214b and 214c, 214d changes over time. This is shown in FIG. 16 as a voltage wave.
[0022]
In FIG. 16, the position of the ladder electrode 202 in the length direction is x, the voltage wave propagating rightward (positive direction of x) is W1 (x, t), and the voltage wave propagating leftward (negative direction of x). Is represented as W2 (x, t).
W1 (x, t) = V0 · sin (ωt + 2π / λ). . . . . (1)
W2 (x, t) = V0 · sin {ωt−2π (x−L0) / λ + Δθ}. . . (2)
Here, ω is the angular frequency of the voltage, λ is the wavelength of the voltage, t is time, L0 is the length of the ladder electrode 2 in the propagation direction, and Δθ is the phase difference. The composite wave W (x, t) of the voltage is as follows.
W (x, t) = W1 (x, t) + W2 (x, t) = 2 · V0cos {2π (x−L0 / 2) / λ−Δθ / 2} · sin {ωt + (2πL0 / λ + Δθ / 2} (3)
[0023]
FIG. 17 conceptually shows the composite wave W (x, t) expressed by the above equation (3). When Δθ = 0, the intensity of the generated plasma is strong at the center of the ladder electrode (x = L0 / 2), and weak at both ends. The strong part of the plasma is the right end of the ladder electrode when Δθ> 0, and the left end when Δθ <0. That is, by using the phase shifter 234 to change Δθ of the above equation (3) into a triangular wave shape temporally between −180 degrees and +180 degrees, a plasma having a uniform intensity over time is generated. Is done. As a result, the non-uniformity of the plasma intensity is averaged over time, so that a microcrystalline Si film having a uniform film thickness distribution can be obtained.
[0024]
[Patent Document 1]
JP-A-8-325759 (page 2-9, FIG. 1-4)
[Patent Document 2]
JP-A-4-237781 (Pages 2-4, Fig. 1-4)
[Patent Document 3]
JP 2001-257098 A (page 3-8, FIG. 1-3)
[0025]
[Non-patent document 1]
L. Sansonnens, A .; Pletzer, D.A. Magni, A .; A. Howling, Ch. Hollenstein and J.M. P. M. Schmitt ,: A voltage uniformity study in large-area reactors for RF plasma deposition, Plasma Source Sci. Technol. 6 (1997) p. 170-178
[0026]
[Problems to be solved by the invention]
By the way, the above-mentioned surface treatment technology, that is, the surface treatment apparatus and the surface treatment method are used in any industrial fields such as LCDs, LSIs, electronic copiers, and solar cells to reduce product cost and improve large-area wall mounting due to improved productivity. The need for large area, uniformity, and high-speed processing for improving performance (specifications) such as TV is increasing year by year.
[0027]
In recent years, in order to meet the above needs, not only in the industry but also in academic societies, both plasma CVD (chemical vapor deposition) technology and plasma etching technology have high density plasma and low electron temperature in the VHF band ( Advanced research and development on large-area, high-speed film formation and large-area, high-speed plasma etching of high-density plasma CVD using a power supply of 30 MHz to 300 MHz) has been active. However, in the prior art, since the following problems still exist, it is difficult to meet the above needs.
[0028]
(1) In the VHF plasma generation for a large-area substrate in the first typical example of the prior art using a plate electrode, according to Patent Literature 1, Patent Literature 3, and Non-Patent Literature 1, a power supply line and It is pointed out that the electric field distribution between the pair of plate electrodes becomes non-uniform and non-uniform due to factors such as the generation of a standing wave peculiar to VHF on the electrodes and the increase in impedance due to the skin effect. Have been.
[0029]
The present inventor has recently shown that the following three items are related to the essential causes relating to the difficulty in increasing the area, making the surface uniform, and increasing the speed of processing by the VHF plasma using the conventional flat plate electrode. discovered.
[0030]
The first is the following structural problem of the feed line. In FIGS. 11 and 12, the connection between the coaxial cable and the electrode is formed by connecting lines having different structures from each other, and it is considered that power reflection occurs at the connection point. That is, the coaxial cable is a transmission system in which the inner surface of the inner conductor (core wire) and the inner surface of the outer conductor are used as the outward route and the return route. On the other hand, the structure of a pair of electrodes is a structure corresponding to two parallel lines unlike a coaxial cable. Therefore, a radio wave reflection phenomenon occurs at the boundary between the two. This phenomenon is accompanied by generation of a leakage current described below. FIG. 18 conceptually shows this state. Although FIG. 18 conceptually shows a moment of high-frequency power current at the junction between the end of the coaxial cable 116c and the pair of electrodes 102 and 104, it is an AC phenomenon, so it is naturally shown in FIG. The direction of the current changes with time.
[0031]
FIG. 18 shows a phenomenon in which the current I flowing inside (the inner surface) of the outer conductor of the coaxial cable 116c is reflected at the end surface of the outer conductor, and a part of the current I leaks to the outer side (outer surface) of the outer conductor. . The current I1 flowing outside the outer conductor (referred to herein as leakage current) returns to the core of the coaxial cable 116c in a form coupled to the wall of the internal structure of the vacuum vessel 101. Since the leakage current I1 is also affected by the structure of the joint and the shape of the specific internal structure of the vacuum vessel, the current I2 flowing between the pair of electrodes 102 and 104 is difficult to control and has no reproducibility. . As a result, it is difficult to achieve a uniform electric field distribution between the pair of electrodes 102 and 104.
[0032]
The second and third problems are related to a detecting means of a reflected wave on the feeder line and a method of suppressing the reflected wave, respectively. The power supply system according to the first typical prior art has the configuration shown in FIG. More specifically, the power supply system shown in FIG. 11 uses a high-frequency power supply having the configuration shown in FIG. That is, the matching wave 117 is adjusted while looking at the detectors of the traveling wave B and the reflected wave B attached to the high frequency power supply to suppress the reflected wave B (to reduce the reflected wave B to about 1 to 10% of the traveling wave power). Adjustment). However, this method has a function that, when the reflected wave A from the downstream side of the matching unit 117 returns to the matching unit 117 as shown in FIG. 19, the matching unit 117 returns it to the downstream side. Therefore, the detector of the traveling wave B / reflected wave B cannot determine the presence or absence of the reflected wave A to the matching unit 117. That is, there is a problem that the state of the reflected wave A on the downstream side of the matching unit 117 cannot be grasped. Since the reflected wave cannot be detected, there is a problem that it cannot be suppressed.
[0033]
(2) Next, a problem with a technique using a ladder electrode of a second typical example of the prior art will be described. Also in the present technology, in addition to the above-mentioned problems, that is, the problems pointed out in Patent Literature 1, Patent Literature 3, and Non-Patent Literature 1, the following three items are the causes of essential and practical problems. I discovered that.
[0034]
The first problem is similar to the first problem in the above item (1). In FIGS. 14 and 15, at the connection between the core wire of the coaxial cable and the ladder electrode, a leakage current is generated from the outer conductor end of the coaxial cable. This is the same as in FIG. However, in the second typical technique, in addition to the problem in the case of the first conventional example, since the bonding portion is in the vacuum vessel, the strong leakage caused by the leakage current at the time of plasma generation is caused. Generates local discharge. This is a problem that causes non-uniformity of plasma, and also makes it difficult to obtain a reproducible and uniform film thickness distribution.
[0035]
The second and third problems are the same as the second and third problems in the above (1), respectively. Also in this case, since the power supply system is configured as shown in FIG. 14, the matching unit 217 is adjusted while looking at the detectors of the traveling wave B and the reflected wave B attached to the high frequency power supply as shown in FIG. By doing so, the reflected wave B is suppressed (the reflected wave is adjusted to about 1 to 10% of the traveling wave power). However, in this method, when the reflected wave A from the downstream side of the matching unit 217 returns to the matching unit 217, the matching unit 217 has a function of returning it to the downstream side. The detector of the reflected wave B cannot determine the presence or absence of the reflected wave A to the matching unit 217. That is, there is a problem that the state of the reflected wave A on the downstream side of the matching unit 217 cannot be grasped. Since the reflected wave cannot be detected, there is a problem that it cannot be suppressed.
[0036]
As described in detail above, the prior art is still difficult to apply in applications such as VHF plasma CVD and plasma etching for large-area substrates required for mass productivity improvement and cost reduction, for example, large-area substrates of a size of 1 mx 1 m. Is considered impossible. Under such circumstances, research has been actively conducted at related societies such as the Japan Society of Applied Physics and the Institute of Electrical Engineers of Japan. However, successful examples of surface treatment methods and devices using VHF plasma for 1mx1m class large area substrates have been announced. It has not been.
[0037]
Therefore, the present invention has been made to solve the above-mentioned problem, and it has been proposed to use a VHF band (30 MHz to 300 MHz) frequency for a large area substrate of, for example, 1 mx 1 m class, which is considered difficult in the prior art. Another object of the present invention is to provide a plasma surface treatment apparatus and a plasma surface treatment method which are excellent in uniformity.
[0038]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a vacuum vessel having an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, and a substrate are set. A pair of electrodes including a first electrode and a second electrode opposed to the first electrode, and a power supply system for supplying high-frequency power between the pair of electrodes. A balance-unbalance conversion device used in combination with the power supply system, In a plasma surface treatment apparatus for treating the surface of the substrate using the generated plasma, The balanced-to-unbalanced conversion device is a tube-shaped conductor having both ends open at both ends of a coaxial cable comprising a core wire, a dielectric material, and an external conductor, and the other end portion of the coaxial cable being an input portion. And one end face is covered with an open cylindrical conductor, the outer surface of the tubular conductor and the inner surface of the cylindrical conductor are in close contact, and the other end face of the cylindrical conductor is connected to the outer conductor of the coaxial cable. The distance between one end face of the tubular conductor and the closed end face of the cylindrical conductor is one-fourth of the wavelength λ of the high-frequency power supply output considering the shortening rate, that is, λ. / 4, and the distance between the outer conductor of the coaxial cable and the inner surface of the tubular conductor is 2 mm to 60 mm, and an insulating ring is provided between the tubular conductor and the outer conductor of the coaxial cable. And a core wire at the other end of the coaxial cable and an external conductor are used as an output unit. And the balance-unbalance converter is The power supply system is characterized in that it is inserted into a connecting portion between a coaxial cable and a pair of electrodes as a component of the power supply system.
[0039]
Similarly, in order to achieve the above object, the invention according to claim 2 of the present application provides a vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, and a substrate. And a power supply system for supplying high-frequency power between the pair of electrodes, the pair of electrodes being composed of a first electrode to be formed, a second electrode opposed to the first electrode, and a second electrode. In a surface treatment apparatus that treats the surface of a substrate by using a substrate, a connection portion between a coaxial cable and a pair of electrodes of a component of the power supply system is configured to match transmission characteristics between lines having different structures from each other. It is characterized by having a configuration in which a balanced conversion device is inserted, and a standing wave detection device that detects a standing wave is inserted between the matching device of the constituent members of the power supply system and the pair of electrodes. I do.
[0040]
Similarly, in order to achieve the above object, an invention according to claim 3 of the present application is directed to a vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, and a substrate. And a power supply system for supplying high-frequency power between the pair of electrodes, the pair of electrodes being composed of a first electrode to be formed, a second electrode opposed to the first electrode, and a second electrode. In a surface treatment apparatus that treats the surface of a substrate by using a substrate, a connection portion between a coaxial cable and a pair of electrodes of a component of the power supply system is configured to match transmission characteristics between lines having different structures from each other. A balancing converter is inserted, and a standing wave detector that detects a standing wave between the matching device of the power supply system component and the pair of electrodes is inserted, and the pair of electrodes includes: There is a parallel relationship with the impedance of the pair of electrodes. It characterized by having a structure that reactance adjuster is added.
[0041]
Since the reactance adjusting device is set in parallel with the pair of electrodes 2 and 4, the high-frequency power supply 15 uses the combined impedance of the pair of electrodes and the reactance in a plasma generation state as a load. become.
[0042]
Similarly, in order to achieve the above object, the invention described in claim 4 of the present application Claims 2 and 3 In the balanced-unbalanced conversion device, the core wire and the external conductor at one end of a coaxial cable including a core wire, a dielectric material, and an external conductor are used as an input unit, and the length is reduced to the other end of the coaxial cable. At a quarter of the wavelength λ of the output of the high-frequency power supply, that is, λ / 4 in consideration of the ratio, the cylindrical conductor having a distance of 2 mm to 60 mm from the outer conductor is covered, and one of the cylindrical conductors is covered. An end face is opened, the other end face is brought into close contact with the outer conductor of the coaxial cable, an insulating ring is provided between the cylindrical conductor and the coaxial cable, and a core wire at the other end of the coaxial cable is provided. And an external conductor as an output unit.
[0043]
In the above-mentioned claim 4 (the same applies to other claims), the wavelength λ in consideration of the shortening rate is the wavelength of the radio wave when propagating inside the coaxial cable. It means the product of 0.67 in the case of polyethylene or 0.34 in the case of alumina and the wavelength of the radio wave corresponding to the high frequency power supply output frequency when propagating in a vacuum.
[0044]
Similarly, in order to achieve the above object, the invention of claim 5 of the present application Claims 2 and 3 In the above-mentioned balanced-unbalanced conversion device, the core wire and the external conductor at one end of a coaxial cable composed of a core wire, a dielectric material and an external conductor are used as an input portion, and the other end of the coaxial cable is provided with a tube having both ends open. The cylindrical conductor is covered with a cylindrical conductor whose one end face is open, the outer surface of the tubular conductor and the inner surface of the cylindrical conductor are adhered, and the other end face of the cylindrical conductor is the same as that of the coaxial cable. The distance between one end face of the tubular conductor and the closed end face of the cylindrical conductor is a quarter of the wavelength λ of the high-frequency power supply output in consideration of the shortening rate. In other words, the distance between the outer conductor of the coaxial cable and the inner surface of the tubular conductor is 2 mm to 60 mm, and insulation is provided between the tubular conductor and the outer conductor of the coaxial cable. Install a ring and connect the core wire at the other end of the coaxial cable to the external conductor. It characterized by having a configuration in which an output unit.
[0045]
Similarly, in order to achieve the above object, the invention of claim 6 of the present application Claims 2 and 3 , The balanced-to-unbalanced conversion device includes a core and an external conductor at one end of a first coaxial cable including a core, a dielectric, and an external conductor as an input unit, and the other end of the first coaxial cable as an input. The outer conductors at both ends of the second coaxial cable having a U-shape and a length of の of the wavelength λ of the output of the high-frequency power supply, that is, considering the shortening rate, that is, λ / 2, are connected to the outer conductor. And connecting the core wire at the other end of the first coaxial cable to one core wire of the U-shaped second coaxial cable, and connecting the other core wire of the U-shaped second coaxial cable. And a core wire at the other end of the first coaxial cable as an output unit.
[0046]
Similarly, in order to achieve the above object, the invention according to claim 7 of the present application is directed to a vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, and a substrate set. A pair of electrodes including a first electrode to be formed and a second electrode opposed to the first electrode, and a power supply system for supplying high-frequency power between the pair of electrodes. A balance-unbalance conversion device used in combination with the power supply system, Comprising, in a plasma surface treatment method for treating the surface of the substrate using the generated plasma, The balanced-to-unbalanced conversion device is a tube-shaped conductor having both ends open at both ends of a coaxial cable comprising a core wire, a dielectric material, and an external conductor, and the other end portion of the coaxial cable being an input portion. And one end face is covered with an open cylindrical conductor, the outer surface of the tubular conductor and the inner surface of the cylindrical conductor are in close contact, and the other end face of the cylindrical conductor is connected to the outer conductor of the coaxial cable. The distance between one end face of the tubular conductor and the closed end face of the cylindrical conductor is one-fourth of the wavelength λ of the high-frequency power supply output considering the shortening rate, that is, λ. / 4, and the distance between the outer conductor of the coaxial cable and the inner surface of the tubular conductor is 2 mm to 60 mm, and an insulating ring is provided between the tubular conductor and the outer conductor of the coaxial cable. And a core wire at the other end of the coaxial cable and an external conductor are used as an output unit. And the balance-unbalance converter is Inserted into the connection between the coaxial cable of the power supply system and the pair of electrodes Is The transmission characteristics of the two are matched, and power is supplied between the pair of electrodes.
[0047]
Similarly, in order to achieve the above object, an invention according to claim 8 of the present application provides a vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, and a substrate set. And a power supply system for supplying high-frequency power between the pair of electrodes, the pair of electrodes being composed of a first electrode to be formed, a second electrode opposed to the first electrode, and a second electrode. In a surface treatment apparatus that treats the surface of a substrate by using a device, a balance-unbalance conversion device is inserted into a connection portion between the coaxial cable of the power supply system and the pair of electrodes, and the transmission characteristics of both devices are adjusted. Matching, and a standing wave detector is inserted between the matching device of the component of the power supply system and the pair of electrodes, a standing wave between them is measured, and the measured value of the standing wave detector is measured. That is, based on the VSWR value, the power supply line of the power supply system is And controlling the standing wave.
[0048]
Similarly, in order to achieve the above object, the invention according to claim 9 of the present application is directed to a vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, and a substrate. And a power supply system for supplying high-frequency power between the pair of electrodes, the pair of electrodes being composed of a first electrode to be formed, a second electrode opposed to the first electrode, and a second electrode. In a surface treatment method for treating the surface of a substrate by using a device, a balance-unbalance conversion device is inserted into a connection portion between the coaxial cable of the power supply system and the pair of electrodes to match the transmission characteristics of the two. And, a standing wave detector is inserted between the matching device of the power supply system constituent member and the pair of electrodes, and a standing wave between them is measured, and the pair of electrodes is connected to the pair of electrodes. Reactance adjustment in parallel with impedance between electrodes Adding device, based on the measured value or VSWR value of the standing wave detection apparatus, and controls the standing wave feed line constituting the reactance and said power supply system of the reactance adjusting apparatus.
[0049]
Similarly, in order to achieve the above object, the invention according to claim 10 of the present application is characterized in that, in claims 7 to 9, the measured value of the standing wave detector, that is, the VSWR value is 2.5 or less. I do.
[0050]
The VSWR value is 2.5 or less because the value is approximately 18% in terms of power, and if it is within the range, there is no practical problem.
[0051]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a surface treatment apparatus and a surface treatment method according to an embodiment of the present invention will be described with reference to the drawings. In the following description, as an example of a surface treatment apparatus and a surface treatment method, an apparatus and a method for producing an a-Si thin film necessary for producing a solar cell are described. It is not limited to the example apparatus and method.
[0052]
(Example 1)
First Embodiment A plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) according to a first embodiment will be described with reference to FIGS. FIG. 1 is a schematic diagram showing the entire plasma surface treatment apparatus according to the first embodiment, FIG. 2 is a block diagram of the plasma surface treatment apparatus of FIG. 1, and FIG. FIG. 4 is an explanatory diagram showing a first specific example of the unbalanced converter, and FIG. 4 is an explanatory diagram showing a first specific example of the balanced-unbalanced device incorporated in the plasma surface treatment apparatus of FIG.
[0053]
First, the configuration of the device will be described. 1 and 2, reference numeral 1 denotes a vacuum container. The vacuum vessel 1 is provided with a pair of electrodes for converting discharge gas into plasma, which will be described later, that is, a first non-grounded electrode 2 and a second non-grounded electrode 4 including a substrate heater 3 (not shown). The second non-grounded electrode 4 is fixed to the vacuum vessel 1 with insulator supporting members 5a and 5b. The first non-ground electrode 2 is fixed to the vacuum vessel 1 via an insulator 6 (not shown). A large number of small holes 7 having a diameter of about 2 mm to 10 mm are arranged in the first non-ground electrode 2 at an aperture ratio of 40% to 60%. An earth shield 8 is arranged around the first non-ground electrode 2. The earth shield 8 suppresses discharge in unnecessary portions, and discharges the discharge gas such as SiH 4 supplied from the discharge gas supply pipes 9 a and 9 b to the rectification hole 10 and the non-ground electrode 2. Has a function of supplying uniformly between the pair of electrodes 2 and 4 through the small holes 7. The earth shield 8 is used in combination with the exhaust pipe 11 and a vacuum pump 12 (not shown), and thus has a function of discharging used discharge gas that has been turned into plasma in the plasma generation space.
[0054]
The pressure in the vacuum vessel 1 is monitored by a pressure gauge (not shown) and automatically adjusted and set to a predetermined value by a pressure adjusting valve (not shown). In the case of this 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 1,330 Pa). The ultimate pressure of the vacuum in the vacuum vessel 1 is about 2 to 3E-7 Torr (2.66 to 3.99E-5 Pa).
[0055]
Reference numeral 13 denotes a substrate, which is installed on the second non-grounded electrode 4 by opening and closing a gate valve 39 (not shown). Then, the substrate is heated to a predetermined temperature by a substrate heater 3 (not shown).
[0056]
In FIGS. 1 and 2, reference numeral 15 denotes a high-frequency power supply, which generates power of a frequency of 30 MHz to 300 MHz (VHF band). The power is insulated by the first coaxial cable 16a, the matching unit 17, the second coaxial cable 16b, the current introduction terminal 18, the third coaxial cable 16c, the balun converter 19, and the insulating rings 21a and 21b (not shown). The power is supplied to the power supply points 14 a and 14 b of the pair of electrodes 2 and 4 via the first and second power supply lines 23 and 29.
[0057]
The balance-unbalance converter 19 can be used to connect two lines having different structures, such as a coaxial cable with an external conductor grounded and a non-grounded parallel two line, for example. There is a function to match transmission characteristics. Incidentally, the coaxial cable of the unbalanced line has a transmission form in which the current flows through the core wire on the outward path, flows on the outer conductor and the earth on the return path, and flows reversely. In a balanced line, current flows alternately between two lines as a forward path and a return path, and has a phase difference of 180 degrees with equal amplitude.
[0058]
FIG. 3 shows a first specific example of the balance-unbalance converter 19. The apparatus shown in FIG. 3 uses the core wire and the external conductor at one end of the coaxial cable 16c composed of the core wire 23a, the external conductor 24, and the dielectric 25 as input portions, and uses the other end of the coaxial cable, that is, the pair Has a structure in which a cylindrical conductor 26 is covered on the end connected to the electrodes 2 and 4, and the core wire 23 and the external conductor 29 at the end are used as an output unit. The cylindrical conductor 26 has a cylindrical shape, one end surface of which is open, and the other end surface 27 of which is in close contact with and connected to the external conductor 24. Its length is equal to the product of one-fourth of the wavelength λ of the output power of the high frequency power supply 15 (ie, λ / 4) and the wavelength shortening rate of the coaxial cable, and the distance between the external conductor 24 is 2 mm. It is about 60 mm. Insulating rings 28a and 28b are arranged between the cylindrical conductor 26 and the outer conductor 24, and the interval between them is kept constant. The interval is not particularly limited as long as the insulation property can be ensured, but as a guide, it is about the interval between the pair of electrodes. As shown in FIG. 3, a lead wire 29 is connected to an end of the outer conductor 24, and is used in combination with the core wire 23 to supply power to the feeding points 14a and 14b.
[0059]
In FIG. 3, when a leakage current flows from the point 30a on the end face of the outer conductor 24 to the point 31 on one end face via the point 30b on the other end face of the cylindrical conductor 26, Since the length of the point 30a to the point 30b is equal to the product of the wavelength shortening rate (for example, when the dielectric is polyethylene: 0.67 and alumina: 0.34) and λ / 4, the point The impedance between 30a and point 31 is infinite. As a result, no current leaks from the end face of the outer conductor 24. In other words, there is an effect that current leakage and power reflection are suppressed at the connection between the unbalanced line and the balanced line.
[0060]
A case in which the first specific example 32 of the balance-unbalance conversion device illustrated in FIG. 3 is used as one configuration of the surface treatment device according to the first embodiment illustrated in FIGS. 1 and 2 will be described. FIG. 4 shows a wiring state for connecting the pair of electrodes 2 and 4 shown in FIGS. 1 and 2 to the first specific example 32 of the balun. A feed point 14a located in the small hole 7 portion of the inner surface of the ungrounded electrode 2 which is in contact with the plasma generation space (here, the surface of the non-grounded electrode 2 on the side of the counter electrode is referred to as the inner surface). The core wire 23 of the coaxial cable of the specific example 32 is connected. The lead wire 29 of the first specific example 32 of the balun is connected to a feed point 14b on the inner surface of the ground electrode 4. The core wire 23 and the lead wire 29 are provided with, for example, insulating rings 21a and 21b made of alumina (not shown) to suppress abnormal discharge.
[0061]
Next, a method of forming a-Si for an a-Si solar cell using the plasma surface treatment apparatus having the above-described configuration will be described. 1 to 4, the substrate 13 is previously set on the second non-grounded electrode 4, the vacuum pump 12 is operated to remove the impurity gas and the like in the vacuum vessel 1, and then the discharge gas supply pipe 9a , 9b while supplying a SiH4 gas at a pressure of, for example, 500 sccm and a pressure of 0.5 Torr (66.5 Pa), and supplying a high-frequency power, for example, a power of a frequency of 60 MHz, between the pair of electrodes 2 and 4. The substrate temperature is kept in a range of 80 to 350 ° C., for example, 200 ° C.
[0062]
That is, the output of the high-frequency power supply 15 is, for example, 60 MHz, and the output of 500 W is applied to the first coaxial cable 16a, the matching unit 17, the second coaxial cable 16b, the current introducing terminal 18, the third coaxial cable 16c, the balanced-unbalanced converter. The power is supplied to power supply points 14a and 14b via a first specific example 32 of FIG. 19 and first and second power supply lines 23 and 29 insulated by insulating rings 21a and 21b, respectively. In this case, by adjusting the matching device 17, the reflected wave of the supplied power can be prevented from returning to the upstream side of the matching device 17. As a result, a plasma of SiH4 gas is generated.
[0063]
Here, the power supplied to the feeding points 14a and 14b is reduced by the leakage current prevention function of the first specific example 32 of the balun 19, thereby suppressing the generation of the leakage current, and Can be supplied between the pair of electrodes 2 and 4 from the power supply lines 23 and 29. Therefore, no abnormal discharge such as local discharge occurs near the feeding points 14a and 14b. The insulating effect of the insulating rings 21a, 21b around the first and second power supply lines 23, 29 also suppresses abnormal discharge between the two. Further, in the related art, since the generated leakage current is related to the grounding structure and the wiring state around the pair of electrodes, it is difficult to generate plasma with good reproducibility, but in the present embodiment, since no leakage current is generated, Plasma with good reproducibility can be generated.
[0064]
In the above process, when the SiH4 gas is turned into plasma, radicals such as SiH3, SiH2, and SiH existing in the plasma are diffused by a diffusion phenomenon, and are adsorbed on the surface of the substrate 13, thereby forming an a-Si film. I do. It is a known technique that microcrystalline Si or thin-film polycrystalline Si can be formed by optimizing the flow ratio, pressure and power of SiH4 and H2 in the film forming conditions.
[0065]
Specific conditions for forming a film by the above procedure will be described below. An a-Si film having a film forming speed of 1 nm / s and a film thickness distribution of ± 10% is formed on a glass substrate 13 having a size of about 1200 mm × 300 mm (thickness: 4 mm).
[0066]
The film forming conditions are as follows.
(Film formation conditions)
Discharge gas: SiH4
Flow rate: 500sccm
Pressure: 0.5 Torr (66.5 Pa)
Power frequency: 60 MHz
Power: 500W
Temperature of substrate 13: 200 ° C.
[0067]
When the plasma is generated under the above film forming conditions, the transmission characteristics at the connection between the power supply system and the pair of electrodes are matched by the above-mentioned equilibrium-unbalance converter, and the generation of leakage current is suppressed. The spatial distribution of the density is uniform with good reproducibility as compared with the prior art. As a result, the film thickness distribution of the formed a-Si becomes uniform with good reproducibility as compared with the related art. Numerically, a film can be formed when the a-Si film thickness distribution is within ± 10.
[0068]
In the present embodiment, the number of feed points is set to one (one pair) for each of the pair of electrodes 2 and 4, so that the substrate size is limited to about 1200 mm × 300 mm. However, if the number of feed points is increased, the width of the size is reduced. Naturally, it is scalable.
[0069]
In the manufacture of a-Si solar cells, thin film transistors, photosensitive drums, and the like, there is no problem in performance as long as the film thickness distribution is within ± 10%. According to the above-described embodiment, even when a power supply frequency of 60 MHz is used, a significantly better film thickness distribution can be obtained as compared with the conventional apparatus and method. This means that the industrial value related to improvement in productivity and cost reduction in the field of manufacturing a-Si solar cells, thin film transistors, photosensitive drums and the like is extremely large.
[0070]
(Example 2)
Second Embodiment A plasma surface treatment apparatus and a plasma surface treatment method according to a second embodiment will be described with reference to FIGS. First, the configuration of the device will be described. However, the same members as those in FIGS. 1 to 4 are denoted by the same reference numerals, and description thereof will be omitted. The configuration of the apparatus of the second embodiment is the same as that of the first embodiment, that is, in FIGS. 1, 2, and 4, in place of the first specific example 32 of the balun used as the balun 19. This uses the second specific example 40 of the balance / unbalance device shown in FIG. 5, and all other device components are the same. Therefore, the components of the device other than the second specific example 40 of the balun will be referred to FIG. 1, FIG. 2 and FIG. 4, and the description will be omitted here.
[0071]
FIG. 5 is an explanatory diagram showing a configuration of a second specific example 40 of the balun, which replaces the first specific example 32 of the balun. In FIG. 5, a core wire and an external conductor at one end of the coaxial cable 16c composed of a core wire 23, an external conductor 24, and a dielectric 25 are used as input portions, and the other end of the coaxial cable, that is, the pair of electrodes is used. It has a structure in which a tubular conductor 26a and a cylindrical conductor 26b, both ends of which are open, are placed over the ends connected to the ends 2 and 4, and the core wire 23 and the external conductor 29 at the ends are connected to the output section. And As shown in FIG. 5, the tubular conductor 26a and the cylindrical conductor 26b are in a relationship of an inner cylinder and an outer cylinder, and the outer surface of the tubular conductor 26a and the inner surface of the cylindrical conductor 26b are electrically connected. Short-circuited. The distance between the overlapping portions in the relationship between the inner cylinder and the outer cylinder is adjusted by using mounting bolts 42a, 42b and 41a, 41b described later. The distance between one end face 31 of the tubular conductor 26a and the end face 27 of the cylindrical conductor 26b is a quarter of the wavelength λ of the output power of the high frequency power supply 15 (ie, λ / 4) and the coaxial cable. This is a value equal to the product of the wavelength shortening rate and. The distance between the inner surface of the tubular conductor 26a and the outer conductor 24 is about 2 mm to 60 mm. Insulating rings 28a and 28b are arranged between the tubular conductor 26a and the outer conductor 24, and the interval between them is kept constant. A lead wire 29 is connected to an end of the outer conductor 24, and is used for supplying power to the feeding points 14a and 14b in combination with the core wire 23 as described later.
[0072]
In FIG. 5, a leakage current may flow from the point 30a on the end face of the outer conductor 24 to the point 31 on the end face of the tubular conductor 26a via the point 30b on the end face of the cylindrical conductor 26b. In this case, the length of the point 30a to the point 30b is a value equal to the product of the wavelength shortening ratio (for example, when the dielectric is polyethylene: 0.67 and when the dielectric is alumina: 0.34) and λ / 4. Therefore, the impedance between the point 30a and the point 31 is infinite. As a result, no current leaks from the end face of the outer conductor 24. That is, at the connection between the unbalanced line and the balanced line, there is a function of suppressing current leakage and power reflection.
[0073]
Second Embodiment As a second embodiment, a case will be described in which the second specific example 40 of the balance-unbalance conversion device illustrated in FIG. 5 is used as one configuration of the surface treatment device illustrated in FIGS. 1 and 2. FIG. 4 shows a wiring state for connecting the pair of electrodes 2 and 4 shown in FIGS. 1 and 2 to the first embodiment 32 of the balanced-unbalanced conversion device. A second embodiment 40 of the device is used. A feed point 14a located in the small hole 7 portion of the inner surface of the first non-grounded electrode 2 (here, the surface of the first non-grounded electrode 2 facing the opposite electrode is referred to as the inner surface) in contact with the plasma generation space, The core wire 23 of the coaxial cable of the second embodiment 40 is connected. The lead wire 29 of the second embodiment 40 of the balun converter is connected to the feeding point 14b on the inner surface of the second ungrounded electrode 4. The core wire 23 and the lead wire 29 are provided with, for example, insulating rings 21a and 21b made of alumina (not shown) to suppress abnormal discharge.
[0074]
Next, a-Si for a-Si solar cells was manufactured using the surface treatment apparatus having the above-described configuration.
A method for forming a film will be described. 1, 2 and 5, the substrate 13 is previously set on the second non-grounded electrode 4, and the vacuum pump 12 is operated to remove impurity gas and the like in the vacuum vessel 1. While supplying SiH4 gas from the supply pipes 9a and 9b at, for example, 500 sccm and a pressure of 0.5 Torr (66.5 Pa), high-frequency power, for example, power of a frequency of 70 MHz is supplied between the pair of electrodes 2 and 4. The substrate temperature is maintained in a range of 80 to 350 ° C., for example, 180 ° C.
[0075]
That is, the output of the high-frequency power supply 15 is, for example, 70 MHz, and the output of 500 W is applied to the first coaxial cable 16a, the matching unit 17, the second coaxial cable 16b, the current introducing terminal 18, the third coaxial cable 16c, the balanced-unbalanced converter. The power is supplied to the power supply points 14a and 14b via the first and second power supply lines 23 and 29 which are insulated by the 19 second specific example 40 and the insulating rings 21a and 21b, respectively. In this case, by adjusting the matching device 17, the reflected wave of the supplied power can be prevented from returning to the upstream side of the matching device 17. If the adjustment of the length of the second specific example 40 of the above-mentioned balance-unbalance converter is not matched to the frequency of 70 MHz, the current between the third coaxial cable 16c and the pair of electrodes 2 and 4 may be reduced. Is generated, the plasma generation is temporarily stopped, and the length of the second specific example 40 of the above-mentioned equilibrium-unbalance conversion device is adjusted to generate plasma again, and the above-mentioned power reflection occurs. Can be confirmed that was suppressed.
[0076]
In addition, the function of adjusting the length of the second specific example 40 of the above-mentioned balance-unbalance conversion device can be performed without installing a separate balance-unbalance conversion device when the frequency of the high-frequency power supply 15 is slightly changed. This has the advantage that the length can be adjusted.
[0077]
Here, the power supplied to the feeding points 14a and 14b reduces the power loss by maximizing the effect of the leakage current suppression by adjusting the length of the second specific example 40 of the balun 19. At a minimum, the power can be supplied to the pair of electrodes 2 and 4 from the first and second power supply lines 23 and 29. Therefore, no abnormal discharge such as local discharge occurs near the feeding points 14a and 14b. In addition, the insulating effect of the insulating rings 21a and 21b around the first and second power supply lines 23 and 29 is added, and the abnormal discharge between the two is suppressed.
[0078]
When the SiH4 gas is turned into plasma, radicals such as SiH3, SiH2, and SiH existing in the plasma are diffused by a diffusion phenomenon and are adsorbed on the surface of the substrate 13, whereby an a-Si film is deposited. It is a known technique that microcrystalline Si or thin-film polycrystalline Si can be formed by optimizing the flow ratio, pressure and power of SiH4 and H2 in the film forming conditions.
[0079]
Specific conditions for forming a film by the above procedure will be described below. An a-Si film having a film forming speed of 1 nm / s and a film thickness distribution of ± 10% is formed on a glass substrate 13 having a size of about 1200 mm × 300 mm (thickness: 4 mm).
[0080]
The film forming conditions are as follows.
(Film formation conditions)
Discharge gas: SiH4
Flow rate: 500sccm
Pressure: 0.5 Torr (66.5 Pa)
Power frequency: 70MHz
Power: 500W
Temperature of substrate 13: 200 ° C.
[0081]
When plasma is generated under the above-described film forming conditions, the transmission characteristics at the connection between the power supply system and the pair of electrodes are matched by the above-described equilibrium-unbalance converter, as in the first embodiment, and the generation of leakage current is suppressed. Therefore, the spatial distribution of the density of the generated plasma becomes uniform with good reproducibility as compared with the related art. As a result, the film thickness distribution of the formed a-Si becomes uniform with good reproducibility as compared with the related art. Numerically, a film can be formed when the a-Si film thickness distribution is within ± 10.
[0082]
However, in the second embodiment, since the function of the balance-unbalance conversion device of the device component is different from that of the first embodiment, and the corresponding wavelength has a slight adjustment function, the frequency of the high-frequency power supply 15 is slightly changed. Even in such a case, there is an advantage that the length can be adjusted without separately installing a new balance-unbalance converter.
[0083]
In the second embodiment, each of the pair of electrodes 2 and 4 has one power supply point (one pair). Therefore, the substrate size is limited to about 1200 mm × 300 mm. However, if the number of power supply points is increased, the width of the size is reduced. Is naturally scalable.
[0084]
In the manufacture of a-Si solar cells, thin film transistors, photosensitive drums, and the like, there is no problem in performance as long as the film thickness distribution is within ± 10%. According to the above-described embodiment, even when a power supply frequency of 70 MHz is used, a significantly better film thickness distribution can be obtained as compared with the conventional apparatus and method. This means that the industrial value related to improvement in productivity and cost reduction in the field of manufacturing a-Si solar cells, thin film transistors, photosensitive drums and the like is extremely large.
[0085]
(Example 3)
Another device that may replace the first and second specific examples 32 and 40 of the balun converter 19 shown in FIGS. 4 and 5, that is, a third specific example 50 will be described below as a third example. I do. However, the same members as those in FIGS. 1 to 5 are denoted by the same reference numerals, and description thereof is omitted. The configuration of the device according to the third embodiment is the same as that of the first and second embodiments, that is, the configuration of the balance-unbalance converter used as the balance-unbalance converter 19 in FIGS. 1, 2, and 4. Instead of the first and second specific examples 32 and 40, a third specific example 50 of the balun converter shown in FIG. 6 is used, and all other device configurations are the same. Therefore, for the device components other than the third specific example 50 of the balun converter 19 and the implementation procedure, refer to the first and second embodiments.
[0086]
FIG. 6 is an explanatory diagram showing the configuration of the third specific example 50 of the balance-unbalance conversion device 19. In FIG. 6, the third specific example 50 has a structure in which a second coaxial cable 51 is added to the first coaxial cable 16c. That is, the outer conductors at both ends of the second coaxial cable 51 whose length is one half (ie, λ / 2) of the wavelength λ in consideration of the shortening rate are connected to the pair of electrodes 2 of the first coaxial cable 16c. It is configured to be connected to a short external conductor on the four side by using a conductive plate 52. The core wire 53a of the second coaxial cable 51 is connected to the core wire 23 of the first coaxial cable 16c using a first connector 54a. The core wire 53b of the second coaxial cable 51 is connected to the lead wire 29 using a second connector 54b. An insulating ring (not shown) is provided on the core wire 23 and the lead wire 29 of the first coaxial cable 16c and the core wires 53a and 53b of the second coaxial cable 51 for preventing discharge.
[0087]
When the output of the high-frequency power supply 15 is supplied from one end of the first coaxial cable 16c of the third specific example 50 of the balanced-to-unbalanced converter having the above configuration, similarly to the second and third embodiments, Since the length of the second coaxial cable 51 is one half of the wavelength in consideration of the shortening rate, the lead wire 29 and the core wire 23 are converted into electric power having a voltage / current phase difference of 180 degrees different from each other. . However, the voltage between the lead wire 29 and the core wire 23 is twice the voltage between the core wire of the coaxial cable 16c and the outer conductor. That is, the output impedance of the third specific example 50 of the balun converter is four times that of the coaxial cable 16c. Therefore, the specific example 50 can be effectively used when the impedance on the load side is larger than the impedance of the coaxial cable 16c.
[0088]
(Example 4)
Fourth Embodiment A fourth embodiment according to the present invention will be described with reference to FIGS. FIG. 7 is an explanatory view showing the entire plasma surface treatment apparatus according to the fourth embodiment, and FIG. 8 is an explanatory view of the concept of the power supply system of FIG. First, the configuration of the plasma surface treatment apparatus according to the fourth embodiment will be described. However, the same members as those in FIGS. 1 to 6 are denoted by the same reference numerals, and description thereof will be omitted.
[0089]
In FIG. 7, reference numeral 61 denotes a VSWR meter for measuring a voltage standing wave ratio (abbreviated as VSWR). The VSWR meter measures the voltage of a traveling wave and a reflected wave propagating through a fourth coaxial cable 62 described later. The ratio between the maximum value and the minimum value of the voltage of the standing wave generated by the interference (here, this is expressed as S) is measured and displayed. Reference numeral 62 denotes a fourth coaxial cable, which outputs the output of the high-frequency power supply 15 transmitted from the second coaxial cable 16b via the VSWR meter 61 to the current introduction terminal 18, the third coaxial cable 16c, and the like. To the pair of electrodes 2 and 4.
[0090]
In FIG. 7, a pair of electrodes for converting a discharge gas into plasma, which will be described later, that is, a first non-ground electrode 2 and a second non-ground electrode 4 including a substrate heater 3 (not shown) are arranged in a vacuum vessel 1. I have. The second non-grounded electrode 4 is fixed to the vacuum vessel 1 with insulator support members 5a and 5b (not shown). The first non-ground electrode 2 is fixed to the vacuum vessel 1 via an insulator 6 (not shown). A large number of small holes 7 having a diameter of about 2 mm to 10 mm are arranged in the first non-ground electrode 2 at an aperture ratio of 40% to 60%. An earth shield 8 is arranged around the first non-ground electrode 2. The earth shield 8 suppresses discharge in unnecessary portions, and discharges the discharge gas such as SiH 4 supplied from the discharge gas supply pipes 9 a and 9 b to the rectification hole 10 and the non-ground electrode 2. Has a function of supplying uniformly between the pair of electrodes 2 and 4 through the small holes 7. The earth shield 8 is used in combination with the exhaust pipe 11 and a vacuum pump 12 (not shown), and thus has a function of discharging used discharge gas that has been turned into plasma in the plasma generation space.
[0091]
The pressure in the vacuum vessel 1 is monitored by a pressure gauge (not shown) and automatically adjusted and set to a predetermined value by a pressure adjusting valve (not shown). In the case of this 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 1,330 Pa). The ultimate pressure of the vacuum in the vacuum vessel 1 is about 2 to 3E-7 Torr (2.66 to 3.99E-5 Pa).
[0092]
The substrate 13 is installed on the second non-grounded electrode 4 by opening and closing a gate valve 39 (not shown). Then, the substrate is heated to a predetermined temperature by a substrate heater 3 (not shown).
[0093]
The high-frequency power supply 15 generates power having a frequency of 30 MHz to 300 MHz (VHF band). The electric power is supplied to the first coaxial cable 16a, the matching unit 17, the second coaxial cable 16b, the VSWR meter 61, the fourth coaxial cable 62, the current introducing terminal 18, the third coaxial cable 16c, and the unbalance converter 19. The power is supplied to the power supply points 14a and 14b of the pair of electrodes 2 and 4 via first and second power supply lines 23 and 29, which are insulated by insulating rings 21a and 21b (not shown).
[0094]
As the unbalance converter 19, for example, the first specific example 32 of FIG. 3, the second specific example 40 of FIG. 5, and the third specific example 50 of FIG. Here, for example, the second specific example 40 is used.
[0095]
Here, features of the power supply system including the VSWR meter 61 will be described. High-frequency power supply 15, first coaxial cable 16a, matching device 17, second coaxial cable 16b, VSWR meter 61, fourth coaxial cable 62, current introduction terminal 18, third coaxial cable 16c, balanced-unbalanced converter A power supply system composed of first and second power supply lines 23 and 29 insulated by 19 and insulating rings 21a and 21b (not shown) is conceptually represented as shown in FIG. That is, the output power Pt1 of the high-frequency power supply 15 is supplied as a traveling wave Pf1 to the load 63 consuming the power, that is, the plasma generated between the pair of electrodes 2 and 4 via the matching unit 17 and the VSWR meter 61, Power Pl is consumed. First, while adjusting the reactance (L and C) of the matching device 17, the L and C are adjusted and set by a traveling wave / reflected wave monitor attached to the high frequency power supply 15 so that the reflected wave Pr1 becomes a minimum value. Next, the VSWR meter 61 measures and evaluates whether or not the power Pt2 transmitted from the matching device 17 to the load 63 is efficiently transmitted to the load 63. That is, the information regarding the maximum voltage and the minimum voltage of the standing wave generated by the traveling wave Pf2 from the matching device 17 to the load 63 and the reflected wave Pr2 from the load 63 toward the matching device 17 is represented by S (ie, VSWR). Read with the value of If S = about 3 or more, for example, adjustment of the length of the second specific example 40 of the balance-unbalance converter 19 of the power supply system component, or adjustment of the length of the current introduction terminal 18 and the third coaxial The tightening condition of the nut at the connection portion with the cable 16c is adjusted. If there is no change in the value of S in the above adjustment, the lengths and specifications of the second, third, and fourth coaxial cables are changed and replaced. In general, if there is no abnormality in the joint portion of the coaxial cable, S is about S = 3 or less. In addition, the fact that the standing wave of the power supply line of the power supply system can be controlled based on the S value measured by the VSWR meter can be said to be a revolutionary means and method not found in the prior art.
[0096]
Further, instead of the VSWR meter 61, a power detector similar to a traveling wave / reflected wave power detector using a directional coupler attached to the high frequency power supply 15 may be used.
[0097]
Next, a method of forming a-Si for an a-Si solar cell using the plasma surface treatment apparatus having the above-described configuration will be described. In FIG. 7, after the substrate 13 is previously set on the second non-grounded electrode 4 and the vacuum pump 12 is operated to remove impurity gases and the like in the vacuum vessel 1, the discharge gas supply pipes 9a and 9b are used. While supplying SiH4 gas at, for example, 500 sccm and a pressure of 0.5 Torr (66.5 Pa), high-frequency power, for example, power of a frequency of 60 MHz is supplied between the pair of electrodes 2 and 4. The substrate temperature is kept in a range of 80 to 350 ° C., for example, 200 ° C.
[0098]
That is, the output of the high-frequency power supply 15 is, for example, 60 MHz, and the output of 500 W is supplied to the first coaxial cable 16a, the matching unit 17, the second coaxial cable 16b, the VSWR meter 61, the fourth coaxial cable 62, the current introducing terminal 18, 3 via the coaxial cable 16c, the second specific example 40 of the balance-unbalance converter 19, and the first and second feeder lines 23 and 29 insulated by insulating rings 21a and 21b, respectively. , 14b. In this case, by adjusting the matching device 17, the reflected wave of the supply power can be adjusted to be about 1 to 10% of the traveling wave power on the upstream side of the matching device 17. Further, S = 1 to about 3 can be adjusted and set by the measurement of the VSWR meter and the adjustment of the balance-unbalance converter 19 and the like. As a result, the output of the high-frequency power supply can be efficiently supplied to the load 63, so that the reflected wave Pr2 from the load 63 including the power supply line is suppressed. As a result, the uniformity of the SiH4 gas plasma generated between the pair of electrodes 2 and 4 is improved. Since the characteristic impedance of the power supply system and the impedance of the load 63 are not generally the same, it is natural that the reflected wave Pr2 cannot be completely suppressed.
[0099]
As described above, the power supplied to the feeding points 14a and 14b is reduced by the leakage current suppression function of the second specific example 40 of the balun 19 to minimize the power loss and to reduce the power loss to the first level. And the second feeder lines 23 and 29 can supply power between the pair of electrodes 2 and 4 in the same manner as in the first to third embodiments. The second specific example 40 of the unbalance device 19 can be adjusted, and there is a merit that its function can be further enhanced.
[0100]
When the SiH4 gas is turned into plasma, radicals such as SiH3, SiH2, and SiH existing in the plasma are diffused by a diffusion phenomenon, and are adsorbed on the surface of the substrate 13, whereby an a-Si film is deposited. It is a known technique that microcrystalline Si or thin-film polycrystalline Si can be formed by optimizing the flow ratio, pressure and power of SiH4 and H2 in the film forming conditions.
[0101]
Specific conditions for forming a film by the above procedure will be described below. An a-Si film having a film forming speed of about 0.3 nm / s and a film thickness distribution of about ± 10% is formed on a glass substrate 13 having a size of about 1200 mm × 300 mm (thickness: 4 mm).
[0102]
The film forming conditions are as follows.
(Film formation conditions)
Discharge gas: SiH4
Flow rate: 500sccm
Pressure: 0.5 Torr (66.5 Pa)
Power frequency: 60MHz-80MHz
Power: 200W
Temperature of substrate 13: 200 ° C.
[0103]
When the plasma is generated under the above film forming conditions, the transmission characteristics at the connection between the power supply system and the pair of electrodes are matched by the above-mentioned balun, and the leakage current is reduced. Although the occurrence is suppressed, the magnitude of the reflected wave can be measured numerically by using the above-mentioned standing wave detecting device when executing the matching operation. As a result, compared to the first, second, and third embodiments, it is possible to reliably suppress the leakage current and the reflected wave. Therefore, the spatial distribution of the density of the generated plasma becomes significantly more uniform than before. As a result, the film thickness distribution of the formed a-Si becomes uniform with good reproducibility as compared with the related art. Numerically, it is possible to form a film with an a-Si film thickness distribution within ± 10.
[0104]
In this embodiment, the power is set to 200 W in consideration of using a commercially available VSWR meter. In addition, since each of the pair of electrodes 2 and 4 has one power supply point (a pair), the substrate size is limited to about 1,200 mm × 300 mm. However, the width of the size can be increased by increasing the number of power supply points. Some things are natural.
[0105]
In the manufacture of a-Si solar cells, thin film transistors, photosensitive drums and the like, there is no problem in performance as long as the film thickness distribution is within ± 10%. According to the above-described embodiment, even when a power supply frequency of about 60 MHz to 80 MHz is used, a significantly better film thickness distribution can be obtained as compared with the conventional apparatus and method. This means that the industrial value related to improvement in productivity and cost reduction in the field of manufacturing a-Si solar cells, thin film transistors, photosensitive drums and the like is extremely large.
[0106]
(Example 5)
Fifth Embodiment A fifth embodiment according to the present invention will be described with reference to FIGS. FIG. 9 is an explanatory view showing the entire plasma surface treatment apparatus according to the fifth embodiment, and FIG. 10 is an explanatory view of the concept of the power supply system in FIG. First, the configuration of the plasma surface treatment apparatus according to the fifth embodiment will be described. However, the same members as those in FIGS. 1 to 8 are denoted by the same reference numerals, and description thereof will be omitted.
The configurational feature of the fifth embodiment is that the device configuration of the fourth embodiment is different from the device configuration of the fourth embodiment in that the reactance adjustment has a function of adjusting the impedance on the downstream side (in the transmission direction of the power output) as viewed from the balun converter 19. The system 70 is added.
[0107]
9 and 10, a reactance adjustment system 70 includes a reactance adjustment device 71 (this impedance is represented by Zc) inserted in parallel with the impedance Zp of the plasma generated between the pair of electrodes 2 and 4, and a fifth Coaxial cable 77, current introduction terminal 76, sixth coaxial cable 75, second balanced-unbalanced converter 74, and third and fourth power supply lines 72 insulated by insulating rings 78a and 78b. , 73. By the reactance adjusting system 70, the plasma between the pair of electrodes 2 and 4, which is the load of the high-frequency power supply 15, and the combined impedance Z11 of the reactance adjusting system 70 are represented by the following relationship: Zll = Zp · Zc / (Zp + Zc) The adjustment is performed using the reactance adjusting device 71.
[0108]
In FIG. 9 and FIG. 10, the vacuum vessel 1 has a pair of electrodes for converting a discharge gas, which will be described later, into plasma, that is, a first non-ground electrode 2 and a second non-ground electrode 4 including a substrate heater 3 (not shown). Are located. The second non-grounded electrode 4 is fixed to the vacuum vessel 1 with insulator support members 5a and 5b (not shown). The first non-ground electrode 2 is fixed to the vacuum vessel 1 via an insulator 6 (not shown). A large number of small holes 7 having a diameter of about 2 mm to 10 mm are arranged in the first non-ground electrode 2 at an aperture ratio of 40% to 60%. An earth shield 8 is arranged around the first non-ground electrode 2. The earth shield 8 suppresses discharge in unnecessary portions, and discharges the discharge gas such as SiH 4 supplied from the discharge gas supply pipes 9 a and 9 b to the rectification hole 10 and the non-ground electrode 2. Has a function of supplying uniformly between the pair of electrodes 2 and 4 through the small holes 7. The earth shield 8 is used in combination with the exhaust pipe 11 and a vacuum pump 12 (not shown), and thus has a function of discharging used discharge gas that has been turned into plasma in the plasma generation space.
[0109]
The pressure in the vacuum vessel 1 is monitored by a pressure gauge (not shown) and automatically adjusted and set to a predetermined value by a pressure adjusting valve (not shown). In the case of this 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 1,330 Pa). The ultimate pressure of the vacuum in the vacuum vessel 1 is about 2 to 3E-7 Torr (2.66 to 3.99E-5 Pa).
[0110]
The substrate 13 is installed on the second non-grounded electrode 4 by opening and closing a gate valve 39 (not shown). Then, the substrate is heated to a predetermined temperature by a substrate heater 3 (not shown).
[0111]
The high-frequency power supply 15 generates power having a frequency of 30 MHz to 300 MHz (VHF band). The electric power is supplied to the first coaxial cable 16a, the matching unit 17, the second coaxial cable 16b, the VSWR meter 61, the fourth coaxial cable 62, the current introducing terminal 18, the third coaxial cable 16c, and the unbalance converter 19. The power is supplied to the power supply points 14a and 14b of the pair of electrodes 2 and 4 via first and second power supply lines 23 and 29, which are insulated by insulating rings 21a and 21b (not shown). As the unbalance converter 19, for example, the first specific example 32 of FIG. 3, the second specific example 40 of FIG. 5, and the third specific example 50 of FIG. Here, for example, the second specific example 40 is used.
[0112]
In the above configuration, it is conceivable that the balance-unbalance converter 19 is omitted, the impedance of the load is adjusted by the reactance adjustment circuit 71, and the VSWR meter 61 is used for the adjustment.
[0113]
Next, a method of forming a-Si for an a-Si solar cell using the plasma surface treatment apparatus having the above-described configuration will be described. In FIG. 9, after the substrate 13 is previously set on the second non-grounded electrode 4 and the vacuum pump 12 is operated to remove impurity gas and the like in the vacuum vessel 1, the discharge gas supply pipes 9a and 9b are used. While supplying SiH4 gas at, for example, 500 sccm and a pressure of 0.5 Torr (66.5 Pa), high-frequency power, for example, power of a frequency of 60 MHz is supplied between the pair of electrodes 2 and 4. The substrate temperature is kept in a range of 80 to 350 ° C., for example, 200 ° C.
[0114]
That is, the output of the high-frequency power supply 15 is, for example, 60 MHz, and the output of 200 W is supplied to the first coaxial cable 16a, the matching unit 17, the second coaxial cable 16b, the VSWR meter 61, the fourth coaxial cable 62, the current introducing terminal 18, 3 via the coaxial cable 16c, the second specific example 40 of the balance-unbalance converter 19, and the first and second feeder lines 23 and 29 insulated by insulating rings 21a and 21b, respectively. , 14b. In this case, first, the fifth coaxial cable 77 and the current introduction terminal 76 are not connected, and the matching device 17 is adjusted, so that the reflected wave of the supplied power to the upstream side of the matching device 17 becomes The output is adjusted to be about 1 to 10% of the output (traveling wave power) of the high frequency power supply 15. Further, adjustment and setting are performed by measuring the VSWR meter and adjusting the balance-unbalance conversion device 19 and the like so that S = 1 to 3 or so. In addition, the fact that the standing wave of the power supply line of the power supply system can be controlled based on the S value measured by the VSWR meter can be said to be a revolutionary means and method not found in the prior art. Next, the fifth coaxial cable 77 is connected to the current introduction terminal 76, and the impedance Zc is adjusted by using a reactance adjuster 71 added in parallel to the pair of electrodes 2 and 4, that is, by adjusting Zc. Zll, that is, Zll = Zp · Zc / (Zp + Zc) is adjusted. As a result, Z11 can be matched as much as possible to the value of the characteristic impedance of the line of the power supply system. This means that the law of maximum supply power has been realized, and as a result, reflected waves from plasma generated between the pair of electrodes 2 and 4 are significantly reduced.
[0115]
With the above-described device configuration, it is possible to realize that the characteristic impedance of the line of the power supply system and the impedance of the load are substantially equal (the law of the maximum supply power), so that the output of the high-frequency power supply can efficiently output the load 63. Can be supplied to This means that the loss of the supplied power is significantly suppressed as compared with the related art.
[0116]
When the SiH4 gas is turned into plasma, radicals such as SiH3, SiH2, and SiH existing in the plasma are diffused by a diffusion phenomenon, and are adsorbed on the surface of the substrate 13, whereby an a-Si film is deposited. It is a known technique that microcrystalline Si or thin-film polycrystalline Si can be formed by optimizing the flow ratio, pressure and power of SiH4 and H2 in the film forming conditions.
[0117]
Specific conditions for forming a film by the above procedure will be described below. An a-Si film having a film forming speed of about 0.3 nm / s and a film thickness distribution of about ± 10% is formed on a glass substrate 13 having a size of about 1200 mm × 300 mm (thickness: 4 mm).
[0118]
The film forming conditions are as follows.
(Film formation conditions)
Discharge gas: SiH4
Flow rate: 500sccm
Pressure: 0.5 Torr (66.5 Pa)
Power frequency: 60MHz-80MHz
Power: 200W
Temperature of substrate 13: 200 ° C.
[0119]
When the plasma is generated under the film forming conditions, the transmission characteristics at the connection between the power supply system and the pair of electrodes are matched by the standing wave detector and the balance-unbalance converter, as in the fourth embodiment, The generation of a leakage current is suppressed, and the addition of the reactance adjusting device makes it possible to control the load, that is, the generated impedance of the plasma and the combined impedance of the reactance adjusting device. As a result, it is possible to suppress the leakage current and realize the law of the maximum supply power. Therefore, the loss of the supplied power is suppressed, and the spatial distribution of the density of the generated plasma is significantly uniform as compared with the related art. As a result, the film thickness distribution of a-Si to be formed is significantly uniform as compared with the related art. Numerically, it is possible to form a film with an a-Si film thickness distribution within ± 10.
[0120]
In this embodiment, the power is set to 200 W in consideration of using a commercially available VSWR meter. In addition, since each of the pair of electrodes 2 and 4 has one power supply point (a pair), the substrate size is limited to the above-described 1200 mm × 300 mm, but the width of the size can be increased by increasing the number of power supply points. Is a matter of course.
[0121]
In the manufacture of a-Si solar cells, thin film transistors, photosensitive drums and the like, there is no problem in performance as long as the film thickness distribution is within ± 10%. According to the above-described embodiment, even when a power supply frequency of about 60 MHz to 80 MHz is used, a significantly better film thickness distribution can be obtained as compared with the conventional apparatus and method. This means that the industrial value related to improvement in productivity and cost reduction in the field of manufacturing a-Si solar cells, thin film transistors, photosensitive drums and the like is extremely large.
[0122]
【The invention's effect】
As described above, according to the plasma surface treatment apparatus of claim 1, the leakage current can be suppressed by inserting the balanced-unbalanced converter into the connection between the power supply system and the pair of electrodes. The spatial distribution of high-density plasma using a power source in the VHF band (30 MHz to 300 MHz), which has been regarded as difficult, can be made uniform, and uniform surface treatment of the substrate, that is, improvement in film formation rate and etching rate and improvement in uniformity can be achieved. It is possible with good reproducibility. This effect has a remarkable contribution to productivity improvement not only in the industries of photoconductors for LSIs, LCDs and copiers but also in the solar cell industry.
[0123]
According to the plasma surface treatment apparatus of the second aspect, the equilibrium-unbalance conversion device is inserted into the connection between the power supply system and the pair of electrodes, and the standing wave detection device matches the components of the power supply system. By inserting between the electrode and the pair of electrodes, the leakage current can be suppressed, and the standing wave can be detected and controlled, respectively, so that the VHF band (30 MHz to 300 MHz), which has been regarded as difficult in the past, can be used. The spatial distribution of high-density plasma using a power supply can be made uniform with good reproducibility, and uniform surface treatment of the substrate, that is, improvement in film formation rate and etching rate and improvement in uniformity can be made with good reproducibility. This effect has a remarkable contribution to productivity improvement not only in the industries of photoconductors for LSIs, LCDs and copiers but also in the solar cell industry.
[0124]
According to the plasma surface treatment apparatus of the third aspect, the equilibrium-unbalance converter is inserted into the connection between the power supply system and the pair of electrodes, and the standing wave detection device matches the components of the power supply system. Inserted between the vessel and the pair of electrodes, and the reactance adjusting device is added in parallel to the pair of electrodes, so that the leakage current can be suppressed, and the standing wave can be detected and controlled. In addition, since the impedance of the load of the power supply system can be adjusted, the spatial distribution of the high-density plasma using a power supply in the VHF band (30 MHz to 300 MHz), which has been considered difficult in the past, is made uniform, and the output power of the power supply system Loss can be suppressed. That is, it is possible to reduce the power consumption and to perform uniform surface treatment on the substrate, that is, to improve the film formation rate and the etching rate and to improve the uniformity with good reproducibility. This effect greatly contributes to the low cost and the improvement of productivity not only in the industries of photoconductors for LSIs, LCDs and copiers, but also in the solar cell industry.
[0125]
Claims 4 to 6 are the above claims. 2 and 3 It has high value as a reliable means of realizing.
[0126]
According to the plasma surface treatment method of the present invention, the leakage current can be suppressed by matching the transmission characteristics of the connection with the balance-unbalance converter inserted into the connection between the power supply system and the pair of electrodes. Therefore, the spatial distribution of high-density plasma using a power supply in the VHF band (30 MHz to 300 MHz), which has been considered difficult in the past, can be made uniform with good reproducibility, and uniform surface treatment on the substrate, that is, the film forming speed and etching speed can be reduced. And uniformity can be improved. This effect greatly contributes to the low cost and the improvement of productivity not only in the industries of photoconductors for LSIs, LCDs and copiers, but also in the solar cell industry.
[0127]
According to the plasma surface treatment method of claim 8, the transmission characteristics of the connection part are matched by the balance-unbalance conversion device inserted into the connection part between the power supply system and the pair of electrodes, and By controlling the magnitude of the reflected wave from the pair of electrodes by a standing wave detector inserted between the matching device of the constituent member and the pair of electrodes, leakage of the generated waves to the connection portions is controlled. Since the current can be suppressed and the reflected wave can be suppressed, the spatial distribution of the high-density plasma using the power supply in the VHF band (30 MHz to 300 MHz), which has been regarded as difficult in the past, can be made uniform with good reproducibility. Uniform surface treatment, that is, improvement in film formation rate and etching rate and improvement in uniformity are possible. This effect has a remarkable contribution to productivity improvement not only in the industries of photoconductors for LSIs, LCDs and copiers but also in the solar cell industry.
[0128]
According to the plasma surface treatment method of the ninth aspect, the transmission characteristics of the connection part are matched by the balance-unbalance conversion device inserted into the connection part between the power supply system and the pair of electrodes, and A standing wave detecting device inserted between the matching device of the constituent member and the pair of electrodes controls the magnitude of the reflected wave from the pair of electrodes, and is added in parallel to the pair of electrodes. By controlling the reactance of the reactance adjusting device, it is possible to suppress the leakage current generated at the connection portion, suppress the reflected wave, and match the impedance of the power supply system with the impedance of the load. It is possible to equalize the spatial distribution of high-density plasma using a power supply in the VHF band (30 MHz to 300 MHz), which has been regarded as difficult in the past, and to suppress the loss of output power of the power supply system. That is, it is possible to reduce the power consumption and to perform uniform surface treatment on the substrate, that is, to improve the film formation rate and the etching rate and to improve the uniformity with good reproducibility. This effect greatly contributes to the low cost and the improvement of productivity not only in the industries of photoconductors for LSIs, LCDs and copiers, but also in the solar cell industry.
[0129]
The surface treatment method of the tenth aspect has a high value as a reliable method for realizing the seventh and ninth aspects.
[0130]
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an entire plasma surface treatment apparatus according to a first embodiment.
FIG. 2 is an explanatory diagram showing a power supply system in the plasma surface treatment apparatus of FIG. 1 according to the first embodiment.
FIG. 3 is an explanatory view showing a first specific example of a balance-unbalance converter 19, which is one configuration of the plasma surface treatment apparatus of FIG. 1 according to the first embodiment.
FIG. 4 is an explanatory view showing a first specific example of the equilibrium-unbalance converter 19 in the plasma surface treatment apparatus of FIG. 1 according to the first embodiment and a connection portion between a pair of electrodes.
FIG. 5 is an explanatory diagram showing the configuration of a second specific example of the balun converter 19 according to the second embodiment.
FIG. 6 is an explanatory diagram showing a configuration of a third specific example of the balanced-unbalanced converter according to the third embodiment.
FIG. 7 is an explanatory view showing the whole plasma surface treatment apparatus according to a fourth embodiment.
FIG. 8 is an explanatory diagram of a concept of a power supply system according to a fourth embodiment.
FIG. 9 is an explanatory view showing the whole plasma surface treatment apparatus according to a fifth embodiment.
FIG. 10 is an explanatory diagram of a concept of a power supply system according to a fifth embodiment.
FIG. 11 is a configuration diagram of a plasma surface treatment apparatus according to a first representative technique of the related art.
FIG. 12 is an explanatory diagram showing power supply points to electrodes according to the first typical conventional technique.
FIG. 13 is a conceptual diagram of a plasma surface treatment apparatus according to a second conventional technique.
FIG. 14 is a block diagram of a power supply system according to the apparatus shown in FIG. 13;
FIG. 15 is an explanatory diagram showing a power supply point to an electrode according to the apparatus shown in FIG. 13;
FIG. 16 is an explanatory diagram of a voltage wave according to the second conventional technique.
FIG. 17 is an explanatory diagram of a composite wave of voltages according to the second conventional technique.
FIG. 18 is an explanatory diagram showing a concept of a leakage current generated between lines having different structures according to a problem of the related art.
FIG. 19 is an explanatory diagram of a traveling-wave / reflected-wave detecting device attached to a high-frequency power supply according to a conventional technique.
[Explanation of symbols]
1. . . Vacuum vessel 2,
2. . . A first ungrounded electrode,
4. . . A second ungrounded electrode,
5a, 5b. . . Insulation support,
7. . . Stoma,
8. . . Earth shield,
9a, 9b. . . Discharge gas supply pipe,
10. . . Straightening hole,
11. . . Exhaust pipe,
13. . . substrate,
14a, 14b. . . Feeding point,
15. . . High frequency power supply,
16a, 16b, 16c. . . First, second and third coaxial cables;
17． . . Matching device,
18. . . Current introduction terminal,
19. . . Balance-unbalance converter,
23. . . A first feed line,
23a. . . Core wire,
24. . . Outer conductor,
25. . . Dielectric,
26. . . Cylindrical conductor,
26a. . . Tubular conductor,
26b. . . Cylindrical conductor,
27. . . End face,
28a, 28b. . . Insulating ring,
29. . . A second feed line,
32. . . A first specific example of the unbalanced conversion device,
40. . . A second specific example of the unbalanced conversion device,
41a, 41b42a, 42b. . . Mounting bolt,
50. . . A third specific example of the unbalanced conversion device,
51. . . coaxial cable,
52. . . Conductive plate,
53a, 53b. . . Core wire,
54a, 54b. . . First and second connectors,
61. . . VSWR meter,
62. . . A fourth coaxial cable,
70. . . Reactance adjustment system,
71. . . Reactance adjuster,
72, 73. . . Third and fourth power supply lines,
74. . . A second balun converter,
76. . . Current input terminal.

Claims (10)

A vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, a first electrode on which a substrate is set, and a second electrode opposed to the first electrode. A pair of electrodes composed of electrodes, a power supply system for supplying high-frequency power between the pair of electrodes, and a balance-unbalance conversion device used in combination with the power supply system, using generated plasma In a plasma surface treatment apparatus for treating a surface of a substrate, the balance-unbalance conversion device includes a core and an external conductor at one end of a coaxial cable including a core, a dielectric, and an external conductor as input parts, and The other end is covered with a tubular conductor open at both ends and a cylindrical conductor open at one end, and the outer surface of the tubular conductor and the inner surface of the cylindrical conductor are in close contact with each other. Of the coaxial cable is The distance between one end face of the tubular conductor and the closed end face of the cylindrical conductor is one-quarter of the wavelength λ of the high-frequency power supply output in consideration of the shortening rate. That is, the distance between the outer conductor of the coaxial cable and the inner surface of the tubular conductor is 2 mm to 60 mm, and an insulating ring is provided between the tubular conductor and the outer conductor of the coaxial cable. Is installed, and has a configuration in which a core wire and an external conductor at the other end of the coaxial cable are used as an output unit, and the balance-unbalance converter is provided with a coaxial cable as a component of the power supply system. A plasma surface treatment apparatus inserted into a connection portion between the pair of electrodes. A vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, a first electrode on which a substrate is set, and a second electrode provided opposite to the first electrode. A plasma surface treatment apparatus comprising: a pair of electrodes comprising electrodes; and a power supply system for supplying high-frequency power between the pair of electrodes, wherein the plasma surface treatment apparatus treats the surface of the substrate using generated plasma. In the connecting portion between the coaxial cable and the pair of electrodes of the component member, a balance-unbalance conversion device that matches transmission characteristics between lines having different structures is inserted, and the matching device of the power supply system component member A plasma surface treatment apparatus, wherein a standing wave detection device for detecting a standing wave is inserted between the pair of electrodes. A vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, a first electrode on which a substrate is set, and a second electrode provided opposite to the first electrode. A plasma surface treatment apparatus comprising: a pair of electrodes comprising electrodes; and a power supply system for supplying high-frequency power between the pair of electrodes, wherein the plasma surface treatment apparatus treats the surface of the substrate using generated plasma. In the connecting portion between the coaxial cable and the pair of electrodes of the component member, a balance-unbalance conversion device that matches transmission characteristics between lines having different structures is inserted, and the matching device of the power supply system component member A standing wave detecting device that detects a standing wave is inserted between the pair of electrodes, and a reactance adjusting device that is in parallel with the impedance between the pair of electrodes is added to the pair of electrodes. Features Plasma surface treatment apparatus. The balance-unbalance conversion device has a core wire and an external conductor at one end of a coaxial cable composed of a core wire, a dielectric material, and an external conductor as an input unit, and the other end of the coaxial cable has a length with a shortening rate. At a quarter of the wavelength λ of the output of the high-frequency power supply considered, that is, at λ / 4, a cylindrical conductor having a distance of 2 mm to 60 mm from the outer conductor is covered, and one end face of the cylindrical conductor is covered. Open, the other end face is brought into close contact with the outer conductor of the coaxial cable, and an insulating ring is installed between the cylindrical conductor and the coaxial cable, and the core wire at the other end of the coaxial cable is connected to the outside. The plasma surface treatment apparatus according to claim 2 , wherein the plasma surface treatment apparatus has a configuration in which a conductor is used as an output unit. The balanced-to-unbalanced conversion device includes a coaxial cable composed of a core wire, a dielectric material, and an external conductor, which has a core wire at one end and an external conductor as an input portion, and has a tubular conductive material open at both ends at the other end of the coaxial cable. A cylindrical conductor whose one end face is open is covered with the body, and the outer surface of the tubular conductor and the inner face of the cylindrical conductor are in close contact with each other, and the other end face of the cylindrical conductor is the outer conductor of the coaxial cable. And the distance between one end face of the tubular conductor and the closed end face of the cylindrical conductor is a quarter of the wavelength λ of the high-frequency power supply output in consideration of the shortening rate, that is, λ / 4, and the distance between the outer conductor of the coaxial cable and the inner surface of the tubular conductor is 2 mm to 60 mm, and an insulating ring is provided between the tubular conductor and the outer conductor of the coaxial cable. Install, and connect the core wire and the external conductor at the other end of the coaxial cable to the output Plasma surface treatment apparatus according to claim 2 or 3, characterized in that it has a configuration that. The balance-unbalance conversion device includes a core and an external conductor at one end of a first coaxial cable including a core, a dielectric, and an external conductor as an input unit, and an outside of the other end of the first coaxial cable. External conductors at both ends of a second coaxial cable having a U-shape and a length of の of the wavelength λ of the high-frequency power supply output considering the shortening rate, that is, λ / 2, And connecting the core of the other end of the first coaxial cable to one of the cores of the second U-shaped coaxial cable, and connecting the other core of the second U-shaped coaxial cable to the above-mentioned core. 4. The plasma surface treatment apparatus according to claim 2 , wherein a configuration is adopted in which a core wire at the other end of the first coaxial cable is used as an output unit. A vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, a first electrode on which a substrate is set, and a second electrode opposed to the first electrode. A pair of electrodes composed of electrodes, a power supply system for supplying high-frequency power between the pair of electrodes, and a balance-unbalance conversion device used in combination with the power supply system, using generated plasma In the plasma surface treatment method for treating the surface of a substrate, the equilibrium-unbalance converter includes, as an input unit, a core wire and an external conductor at one end of a coaxial cable composed of a core wire, a dielectric, and an external conductor; The other end is covered with a tubular conductor open at both ends and a cylindrical conductor open at one end, and the outer surface of the tubular conductor and the inner surface of the cylindrical conductor are in close contact with each other. Of the coaxial cable is The distance between one end face of the tubular conductor and the closed end face of the cylindrical conductor is one-quarter of the wavelength λ of the high-frequency power supply output in consideration of the shortening rate. That is, the distance between the outer conductor of the coaxial cable and the inner surface of the tubular conductor is 2 mm to 60 mm, and an insulating ring is provided between the tubular conductor and the outer conductor of the coaxial cable. Is installed, and has a configuration in which a core wire and an external conductor at the other end of the coaxial cable are used as an output unit, and the balance-unbalance converter is provided with a coaxial cable as a component of the power supply system. A plasma surface treatment method which is inserted into a connection portion with the pair of electrodes, matches transmission characteristics of the two, and supplies power between the pair of electrodes. A vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, a first electrode on which a substrate is set, and a second electrode provided opposite to the first electrode. A plasma surface treatment method comprising: a pair of electrodes composed of electrodes; and a power supply system for supplying high-frequency power between the pair of electrodes, wherein the surface of the substrate is processed using generated plasma. A balance-unbalance converter is inserted into the connection between the coaxial cable and the pair of electrodes of the constituent members to match the transmission characteristics of the two, and the matching device of the constituent member of the power supply system and the pair of electrodes A standing wave detector is inserted between the two, and a standing wave is measured between them. Based on the measured value of the standing wave detector, that is, the VSWR value, the standing of the feed line constituting the power supply system is determined. Plasma surface characterized by controlling waves Management method. A vacuum vessel provided with an exhaust system, a discharge gas supply system for supplying a discharge gas into the vacuum vessel, a first electrode on which a substrate is set, and a second electrode provided opposite to the first electrode. A plasma surface treatment method comprising: a pair of electrodes composed of electrodes; and a power supply system for supplying high-frequency power between the pair of electrodes, wherein the surface of the substrate is processed using generated plasma. A balance-unbalance converter is inserted into the connection between the coaxial cable of the component and the pair of electrodes to match the transmission characteristics of the two, and the matching device of the component of the power supply system and the pair of electrodes A standing wave detector is inserted between the two to measure a standing wave therebetween, and a reactance adjusting device in parallel with the impedance between the pair of electrodes is added to the pair of electrodes, The measured value of the standing wave detector, ie, V Based on WR value, plasma surface treatment method characterized by controlling the standing wave feed line constituting the reactance and said power supply system of the reactance adjusting apparatus. 10. The plasma surface treatment method according to claim 7, wherein a measured value of the standing wave detector, that is, a VSWR value is 2.5 or less.

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