JP2007220639A - Microwave introduction tool, plasma generator, and plasma treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microwave introduction tool in which effect of plasma density is suppressed and in which a microwave absorption rate (power absorption rate) does not decrease even if the length of the introduction tool is shortened, provide a plasma generating device equipped with this, and a plasma treatment device equipped with this. <P>SOLUTION: This is the microwave introduction tool mounted on a chamber 300 having a space to form the plasma, and provided with a wave guide body 100 protruding from a wall face of the chamber 300 toward the space to form the plasma, and the wave guide body 100 has an inner conductor 100b which is composed of a conductor and extending in one direction, and an outer conductor 100a which is composed of dielectric and covers the inner conductor 100b, and a recess and convex part 120 to influence an effective dielectric constant of the outer conductor 100a is formed on a surface of the outer conductor 100a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a microwave introducer, a plasma generator, and a plasma processing apparatus, and in particular, a microwave introducer that can introduce microwaves into a plasma generation chamber with high efficiency, a plasma generator including the microwave introducer, and an etching The present invention relates to a plasma processing apparatus such as an apparatus.

  The dry process using plasma is used in a wide range of technical fields such as semiconductor manufacturing equipment, surface hardening of metal parts, surface activation of plastic parts, and non-chemical sterilization. For example, in manufacturing semiconductors and liquid crystal displays, various plasma treatments such as ashing, dry etching, thin film deposition, or surface modification are used. The dry process using plasma is advantageous in that it is low-cost, high-speed, and can reduce environmental pollution because it does not use chemicals.

  As a typical apparatus for performing such plasma processing, there is a “microwave excitation type” plasma processing apparatus that excites plasma with microwaves having a frequency of 100 megahertz to several tens of gigahertz. A microwave excitation type plasma source has a lower plasma potential than a high-frequency plasma source, and is therefore widely used for resist ashing without damage and anisotropic etching with a bias voltage applied.

In a microwave excitation type plasma processing apparatus, it is necessary to introduce a microwave into a vacuum chamber. In addition, since semiconductor wafers to be processed and glass substrates for liquid crystal displays have been increasing in size year by year, there is a need for an apparatus that generates high-density and uniform plasma over a large area. Therefore, as a microwave introduction means for generating a high-density and uniform plasma, a technique for projecting a waveguide body made of an inner conductor and an outer conductor into a space for generating plasma in a vacuum chamber has been proposed. (For example, Patent Document 1 or 2)
FIG. 11 is a conceptual diagram of a plasma processing apparatus including a waveguide as disclosed in Patent Document 1 or 2.
The plasma processing apparatus 7 shown in FIG. 11 includes a chamber 3 that can maintain a reduced pressure state. A gas introduction port 5 for introducing the processing gas G from a gas introduction means (not shown) is provided in the ceiling portion of the chamber 3, and an exhaust port 6 for exhausting the inside of the chamber is provided at the bottom. A coaxial waveguide 1 composed of an outer conductor 1 a and an inner conductor 1 b is attached to the ceiling portion of the chamber 7 so as to protrude into the plasma generation chamber 8. The processing chamber 9 in the chamber is provided with a stage 4 on which the workpiece W is placed. A coil 2 for generating a magnetic field is attached to the outer wall surface of the chamber 3 near the plasma generation chamber 8.

Next, the operation of the plasma processing apparatus 7 will be described.
First, the pressure in the chamber 3 is reduced to a predetermined pressure by an unillustrated exhaust means (for example, a vacuum pump) connected to the exhaust port 6. Next, a processing gas G (for example, oxygen or fluorine-containing gas) is introduced from the gas introduction port 5 toward the plasma generation chamber 8 in the chamber. The microwave M generated by the microwave generation means (not shown) is guided to the waveguide portion by a waveguide (not shown). The microwave M guided to the waveguide portion is radiated to the outer conductor 1a through the inner conductor 1b and then introduced into the plasma generation chamber 8 in the chamber. Plasma is generated in the plasma generation chamber 8 by the microwave M introduced in this way. After the plasma is generated once, the microwave M propagates as a surface wave on the boundary between the outer conductor 1a and the plasma, and the plasma Will be absorbed. Here, the plasma is confined in a predetermined place by the magnetic field generated by the coil 2.

  The processing gas G in the plasma generation chamber is decomposed or activated by the plasma generated in this manner, and active species such as radicals and decomposed species are generated. Various treatments are performed on the workpiece W placed on the stage 4 by the generated active species and decomposed species.

On the other hand, Patent Document 3 discloses a plasma generator capable of generating uniform plasma over a large area by providing protrusions with concave and convex portions inside a dielectric window (plasma side). In this plasma generator, the microwave propagates through a waveguide having a waveguide space having a rectangular cross section, and then enters the dielectric transmission window through the slot antenna. The dielectric transmissive window is provided with an uneven portion having a rectangular cross section on the plasma side. When the uneven portion is not provided, the microwave radiated from the slot antenna tends to localize in the vicinity of the slot antenna. On the other hand, by providing the concavo-convex part, the surface wave of the microwave propagates along the concavo-convex part and generates uniform plasma over the entire surface of the transmission window.
Japanese Patent Laid-Open No. 11-102799 JP-A-11-214196 JP 2003-142457 A

  By the way, in a plasma generator, it is extremely important to improve the uniformity of plasma and the efficiency of plasma generation. In order to increase the plasma generation efficiency, it is necessary to increase the absorption rate when the plasma absorbs microwaves. However, in the introducer having the coaxial structure as disclosed in Patent Document 1 or 2, in the case of low-pressure and high-density plasma, the surface wave space attenuation coefficient is low, and thus the attenuation length tends to be long. In order to maintain the absorption rate high, a certain length or more (for example, 10 to 15 cm or more) is absolutely necessary. In order to increase the microwave absorption rate while suppressing the length of the introducer, it is necessary to make microwaves easily absorbed from low density plasma to high density plasma. It is necessary to make microwaves easily pass through the plasma. In order to facilitate the transmission of microwaves, coils and magnets that generate a stronger magnetic field than those for confining the plasma described in Patent Document 1 or 2 in place are required, and the size of the apparatus is excessive. And it was uneconomical.

  On the other hand, the technique disclosed in Patent Document 3 is premised on a structure in which the size of the uneven portion is made constant. However, as will be described later in detail, when the size of the concavo-convex portion is constant, the effective dielectric constant of the waveguide does not necessarily become a value that maximizes the microwave absorption rate.

  The present invention has been made in view of the above circumstances. That is, the present invention relates to a microwave introducer that suppresses the influence of plasma density and does not decrease the microwave absorption rate (power absorption rate) even if the length of the introducer is shortened, a plasma generator equipped with the microwave introducer, and Provided is a plasma processing apparatus.

According to one aspect of the invention,
A microwave introducer attached to a chamber having a space for generating plasma,
A waveguide projecting from the wall surface of the chamber toward the space for generating the plasma;
The waveguide includes an inner conductor made of a conductor and extending in one direction, and an outer conductor made of a dielectric and covering the inner conductor.
Provided is a microwave introducer characterized in that a concavo-convex portion affecting the effective dielectric constant of the outer conductor is formed on the surface of the outer conductor.

According to yet another aspect of the present invention,
A chamber;
The microwave introducer attached to the chamber;
With
There is provided a plasma generating apparatus characterized in that plasma can be generated in a space in which the plasma is generated by a microwave introduced through the waveguide.

According to yet another aspect of the present invention,
Comprising the above plasma generator,
There is provided a plasma processing apparatus characterized in that plasma processing of an object to be processed can be performed by the generated plasma.

  As described above in detail, according to the present invention, there is provided a microwave introducer that suppresses the influence of plasma density and does not decrease the microwave absorption rate (power absorption rate) even if the length of the introducer is shortened. The plasma generating apparatus and the plasma processing apparatus having the same can be provided, and the industrial merit is great.

  Hereinafter, embodiments of the present invention will be described in detail with reference to specific examples.

  Fig.1 (a) is a schematic cross section showing the principal part fundamental structure of the microwave introducer concerning the specific example of this invention. Moreover, FIG.1 (b) is the partially expanded sectional view.

This example is a microwave introducer that can be used in a low-pressure plasma generator. This microwave introducer has a substantially cylindrical waveguide 100 composed of an outer conductor 100a and an inner conductor 100b. The outer conductor 100a is made of a dielectric, and is made of, for example, quartz, alumina, sapphire, aluminum nitride, or the like. However, the material of the outer conductor 100a is not limited to these, and may be any insulating material that is chemically stable and excellent in heat resistance and corrosion resistance.
On the other hand, the inner conductor 100b is made of metal.

  The waveguide 100 is attached so as to protrude from the wall surface of the chamber 300 for generating plasma toward the decompression space inside the chamber 300 (right side in the figure). The microwave M is introduced into the waveguide 100 from the outside of the chamber 300 through the waveguide 200. In the case of the specific example shown in FIG. 1, the waveguide 100 has a substantially cylindrical shape, but is not limited to this, and may have an arbitrary cross-sectional shape. For example, the shape of the cross section cut in the direction perpendicular to the paper surface of FIG. 1A may be a triangle, a quadrangle, a polygon, an ellipse, or an outline formed of an arbitrary straight line or curve. Good.

  In order to maintain the decompressed state inside the chamber 300 (right side in the figure), a waveguide root 110 having an outer diameter larger than that of the waveguide 100 is provided at the base of the waveguide 100, and the O-ring 320 Airtightness is secured. However, the waveguide root 110 and the O-ring 320 are not essential in the present invention, and airtightness may be ensured by other methods.

  And the uneven | corrugated | grooved part 120 for determining the effective dielectric constant of the waveguide 100 is formed in the surface of the outer conductor 100a. In the case of the specific example shown in FIG. 1, the concavo-convex portion is a protrusion having a rectangular cross section.

  Inside the chamber 300, for example, the plasma ignition conditions and the maintenance conditions are often not necessarily the same due to, for example, the gas flow and pressure distribution, or the arrangement of internal structures. On the other hand, the uneven part 120 for determining the effective dielectric constant of the waveguide 100 is formed in the surface of the outer conductor 100a of the microwave introducer of this example. By providing such a concavo-convex portion 120, a high microwave absorption rate (power absorption rate) can be obtained in the microwave introducer of this example. As a result, the plasma can be reliably ignited and stably maintained.

  Further, in the microwave introducer of this specific example, the central axis C1 of the waveguide 100 and the central axis C2 of the waveguide 200 substantially coincide with each other. Furthermore, the cross-sectional dimension of the waveguide 100 is set to a size close to the inner diameter of the waveguide 200. If it does in this way, generation | occurrence | production of the reflected wave when the microwave M which propagated the waveguide 200 is input into the waveguide 100 can be suppressed. As a result, the loss of the microwave M can be suppressed and plasma can be generated with high efficiency.

The operation of the microwave introducer will be described.
In FIG. 1A, a microwave M generated by a microwave generating means (not shown) is guided to a waveguide portion by a waveguide 200. The microwave M guided to the waveguide portion is radiated to the outer conductor 100a through the inner conductor 100b and then emitted to the outside of the waveguide body 100. Then, plasma is generated by the emitted microwave.

Next, the operation of the uneven portion 120 formed on the surface of the outer conductor 100a will be described.
When plasma is generated by the microwave M, it is necessary to effectively absorb the power of the microwave M in the plasma. The microwave absorption rate (power absorption rate) is proportional to the surface wave spatial attenuation coefficient α. The surface wave spatial attenuation coefficient α is proportional to the time attenuation coefficient γ and inversely proportional to the group velocity νg as shown in the following equation.

α = γ / νg (1)

Since the time attenuation coefficient γ is mainly determined by the electron / atom collision frequency, it is strongly influenced by the pressure of the processing gas and its components, which are determined according to the respective process conditions in the manufacturing process of the semiconductor wafer and the like. Therefore, the pressure of the processing gas and its components cannot be changed for the purpose of increasing only the microwave absorption rate (power absorption rate) within the predetermined process conditions. That is, it is difficult to optimize the surface wave space attenuation coefficient α, and hence the microwave absorption rate (power absorption rate), by changing the time attenuation coefficient γ.

  The group velocity νg is determined by the microwave frequency, the plasma density, and the dielectric constant of the dielectric (waveguide). Here, the microwave frequency is almost fixed at an industrial frequency (for example, 2.45 GHz) in consideration of economy and the like. Further, the plasma density is almost determined by each process condition in the manufacturing process of a semiconductor wafer or the like, and cannot be freely changed for the purpose of increasing only the microwave absorption rate (power absorption rate). The material of the dielectric is also limited to a certain material such as quartz or alumina in consideration of economy and chemical resistance, and its dielectric constant is fixed within a substantially constant range. For this reason, it has been difficult to change the surface wave spatial attenuation coefficient α and thus the microwave absorption rate (power absorption rate) by changing the group velocity νg.

  In the present invention, the uneven portion 120 is formed on the surface portion of the outer conductor 100a through which the surface wave propagates. In this way, as will be described later, the effective dielectric constant of the surface portion of the waveguide 100 can be changed by changing the filling factor (ratio occupied by the dielectric portion) of the uneven portion. As a result, it is possible to obtain the waveguide body 100 having the optimum group velocity νg so that the microwave absorption rate (power absorption rate) is maximized in accordance with predetermined process conditions. Further, since the microwave absorption rate (power absorption rate) that decreases when the length of the waveguide is shortened can be increased, the length of the waveguide can be further shortened. This is a case where the surface wave propagates along the convex portion of the waveguide body 100.

  In the present embodiment, the introduction mode of the microwave M may be set to a TEM (Transverse ElectroMagnetic wave) mode without a cut-off. Without the cut-off, there is no requirement for the cross-sectional size of the waveguide 100, and it becomes possible to make the minimum size as much as possible within the range of dealing with the rise in temperature and structural strength.

Hereinafter, as a first specific example of the present invention, an effective dielectric constant when the uneven portion 120 has a rectangular cross section will be described. FIG. 1B is a schematic cross-sectional view showing the concavo-convex portion 120 in an enlarged manner.
When the dielectric constant of the dielectric constituting the outer conductor 100a is εd, the effective dielectric constant ε _eff in the concavo-convex portion 120 is expressed by the following equation, and the dielectric constant ε _d of the dielectric and the dielectric of the plasma An intermediate value between the rate εp.

ε _eff = F · ε _d + (1−F) · ε _p (2)
F = S / ρ

Here, F = s / ρ is the above-mentioned filling factor. By changing the filling factor F, the effective dielectric constant ε _eff of the uneven portion 120 can be changed. The filling rate F is appropriately determined by changing the depth and width of the concavo-convex portion in consideration of the process conditions.

FIG. 2A is a conceptual diagram showing an effective dielectric constant distribution when the uneven portion 120 has a rectangular cross section. In the case of a rectangular cross section, the effective dielectric constant ε _eff in the portion of the concavo-convex portion 120 is as expressed by the equation (2), and the dielectric of the dielectric that constitutes the waveguide 100 depends on the value of the filling factor F. It has a value between the rate ε _p and the dielectric constant ε _p of the plasma.

An effective dielectric constant ε _eff when the cross-sectional shape of the concavo-convex portion 120 is a rectangular cross section as shown in FIG. 1B will be described using a specific example. As described above, since the dielectric material is generally limited, the dielectric constant εd of the dielectric is a value between 4 and 10 (for example, quartz is 3.8, and alumina is 8.5). Is). On the other hand, the dielectric constant ε _{p of} plasma is generally -4 to -10. In such a case, it becomes a problem how to select an effective dielectric constant ε _eff , but as a result of the inventor's research, it is between the dielectric constant ε _d of the dielectric and the dielectric constant ε _p of the plasma. The effective dielectric constant ε _eff may be selected as a value obtained by making the absolute value the same as the value of either the dielectric constant ε _d of the dielectric or the dielectric constant ε _p of the plasma, and having the sign reversed. I understood it.

For example, when the dielectric is quartz and ε _d = 3.8 and the dielectric constant ε _{p of the} plasma is −10, ε _eff = −3.8, and the dielectric is alumina and ε _d = 8. 5. If the dielectric constant ε _{p of the} plasma is −5, ε _eff = 5 may be set. This is because if the effective dielectric constant ε _eff is selected to such a value, surface wave resonance occurs on the surface of the waveguide and the group velocity νg approaches 0, so the surface wave spatial attenuation coefficient α increases. It is believed that there is.

As a second specific example, a case will be described in which the effective dielectric constant ε _eff is changed substantially continuously by changing the filling rate of the concavo-convex portion 120 substantially continuously in the height direction.
That is, by providing a transition region that is made up of a plurality of protrusions or the like in the vicinity of the surface (plasma side) of the outer conductor 100a and that changes the filling rate substantially continuously with respect to the height direction, FIG. As illustrated in c), the effective dielectric constant ε _eff can be changed substantially continuously.

For example, in the specific example shown in FIG. 2B, the dielectric constant ε _eff of the transition region can be continuously changed over a range from the dielectric constant ε _d to ε _p .
Further, in the case of the example shown in FIG. 2 (c), it can be continuously varied over a range of the dielectric constant epsilon _eff of the transition region from the epsilon _eff1 up to the epsilon _eff2.

In this case, the microwave absorption coefficient is included in the range in which the dielectric constant ε _eff of the transition region is changed, since the portion having the optimum effective dielectric constant described in the example of the rectangular protrusion described above is included. A waveguide having the optimum group velocity νg for increasing the (power absorption rate) can be easily obtained.

2B and 2C are merely examples, and various other distributions can be given as the distribution of the dielectric constant ε _eff in the transition region.

FIG. 3 is also a conceptual diagram illustrating the distribution of dielectric constant ε _eff in the transition region.
That is, the dielectric constant ε _eff of the transition region may be changed substantially linearly as shown in FIG. 3A, or may be changed stepwise as shown in FIG. Good. When it is changed stepwise, it cannot be said that it is strictly continuous, but if the change step is made fine, an effect equivalent to a substantially continuous change can be obtained.

FIG. 4 is a schematic view illustrating the shape of the uneven portion 120 on the surface portion of the outer conductor 100a that can be used in the present invention. First, in the case of the specific example shown in FIG. 4A, a plurality of protrusions 100P having a plurality of protrusions having a substantially triangular cross section are provided on the surface (plasma side) of the outer conductor 100a. The region provided with these convex portions 100P acts as a transition region. When the convex portion 100P having a substantially triangular cross section is provided, the maximum value and the minimum value of the dielectric constant ε _eff of the transition region are set as shown in FIG. 2B or FIG. The dielectric constant εd and the dielectric constant εp of the plasma P can be expanded. The height of the convex portion 100P, that is, the width (thickness) of the transition region 100 is desirably smaller than the wavelength of the microwave M, and typically may be about several millimeters, for example.

Next, in the case of the specific example shown in FIG. 4B, a plurality of protrusions 100 </ b> P having a substantially trapezoidal cross section are provided on the surface (plasma side) of the outer conductor 100 a. The region provided with these convex portions 100P acts as a transition region. When a convex portion having a substantially trapezoidal cross section is provided, the maximum value and the minimum value of the dielectric constant ε _eff of the transition region are the dielectric constant εd of the dielectric and the plasma P, respectively, as illustrated in FIG. Does not reach the dielectric constant εp.

Next, in the case of the specific example shown in FIG. 4C, a plurality of protrusions 100 </ b> P with a plurality of protrusions having a substantially trapezoidal cross section and curved side surfaces are provided on the surface (plasma side) of the outer conductor 100 a. ing. The region provided with these convex portions 100P acts as a transition region. Also in this specific example, as illustrated in FIG. 2C, the maximum value and the minimum value of the dielectric constant ε _eff of the transition region reach the dielectric constant εd of the dielectric and the dielectric constant εp of the plasma P, respectively. Absent.

Further, in the case of the specific example shown in FIG. 4D, a protrusion 100P having a ridge shape whose cross section converges in a substantially step shape toward the tip is provided on the surface (plasma side) of the outer conductor 100a. Yes. As described above, when the substantially step-like cross-sectional shape is adopted, the change in the average dielectric constant ε _eff is also substantially step-like. However, if the change step is made fine to some extent, the change in the dielectric constant ε _eff is substantially reduced. It can be continuous, ie substantially continuous.

FIG. 5 is a schematic diagram showing another specific example of the concavo-convex portion 120 on the surface portion of the outer conductor 100a that can be used in the present invention.
That is, as shown in FIG. 5A, by providing a plurality of pin-shaped or cone-shaped protrusions 100P on the surface (plasma side) of the waveguide 100, the effective dielectric constant ε _eff is substantially continuous. Can be changed.

  In this case, the shape of the protrusion 100P may be substantially conical as shown in FIG. 5B, or may be substantially frustoconical as shown in FIG. As shown in d), it may be in the form of a curved rotating body, or as shown in FIG. Furthermore, as shown in FIG. 5F, it may have a shape that converges in a substantially staircase pattern toward the tip.

In any of these cases, the dielectric constant ε _eff can be changed continuously or substantially continuously in the transition region.

FIG. 6 is a schematic diagram showing still another specific example of the uneven portion 120 on the surface portion of the outer conductor 100a that can be used in the present invention.
That is, as shown in FIG. 5A, the effective dielectric constant ε _eff can be continuously changed by providing a plurality of pre-drawn holes 100H.
In this case, the shape of the hole 100H may be a substantially conical shape as shown in FIG. 5B, or a substantially truncated cone shape as shown in FIG. It may be a curved rotating body as shown, or a shape with its apex cut out as shown in FIG. Furthermore, as shown in FIG. 5F, the shape may converge in a substantially step shape toward the tip (bottom of the hole).

In addition to the examples shown in FIGS. 4 to 6, similar effects can be obtained by providing convex portions, protrusions, or holes having various shapes. Further, these convex portions, protrusions, and holes may be appropriately combined. That is, in the present invention, any structure may be used as long as the dielectric constant ε _eff continuously changes on the surface (plasma side) of the outer conductor 100a.

  As described above, by changing the effective dielectric constant of the surface portion of the waveguide 100, a microwave introducer having the optimum group velocity νg, and hence the highest microwave absorption rate (power absorption rate) can be easily obtained. be able to.

The effects of the present invention will be further described.
In the introducer having the coaxial structure as disclosed in Patent Document 1 or 2, in the case of low-pressure and high-density plasma, the surface wave spatial attenuation coefficient is low, and thus the attenuation length tends to be long. In order to maintain a high (power absorptance), it has been necessary to make the length of the waveguide more than a certain value (for example, 10 to 15 cm or more). However, if the effective dielectric constant of the surface portion of the waveguide 100 can be set to an optimum value as a result of the study by the present inventors, the microwave absorption rate (power absorption rate) can be obtained even if the length of the waveguide is the same. ) Can be doubled. This means that the same microwave absorption rate (power absorption rate) can be obtained even if the length of the waveguide is shortened to about 1/4 as judged from the attenuation length, which cannot be achieved by the conventional technology. In addition, an introducer having a very short length can be easily obtained. In this case, it is needless to say that a special device (for example, a coil or a magnet that generates a strong magnetic field) conventionally required for shortening the length of the waveguide is unnecessary.

Next, the distribution of the concavo-convex portions in this embodiment will be described.
The specific example described above has a structure in which uneven portions are provided substantially uniformly on the surface of the outer conductor, but it is also possible to change the plasma distribution by changing the distribution of the uneven portions. For example, when the uneven portions are provided substantially uniformly, a large amount of plasma tends to be generated at the base portion of the outer conductor 100a (side closer to the waveguide 200). For this reason, the chamber wall surface near the root of the outer conductor 100a may be sputtered to cause metal contamination. In such a case, spattering of the chamber wall surface is prevented by guiding the plasma generation location to the front end side of the outer conductor 100a by unevenly distributing the uneven portion on the front end side (the side far from the waveguide 200) of the outer conductor 100a. Metal contamination can be prevented. The effective dielectric distribution can also be changed by appropriately selecting the dimension between the recesses (or the dimension between the projections).

Next, a plasma generation apparatus and a plasma processing apparatus using the microwave introducer of the present invention will be described.
FIG. 7 is a conceptual diagram for explaining a basic configuration of a main part of the plasma processing apparatus according to the embodiment of the present invention.
FIG. 8 is a schematic plan view illustrating the arrangement of the microwave introducers when the chamber 300 is viewed from above.

  The plasma processing apparatus of the present embodiment is capable of performing plasma processing in a reduced pressure state, and includes a chamber 300 and a waveguide body 100 attached thereto. The waveguide 100 is the waveguide of the microwave introducer according to the embodiment of the present invention described above with reference to FIGS. For example, as illustrated in FIG. 8, the waveguides 100 can be arranged at equal intervals on the same circumference as viewed from the central axis of the chamber 300. The microwaves M are introduced into the waveguides 100 from the waveguide 200.

  On the other hand, the interior of the chamber 300 can be maintained in a reduced pressure state by the exhaust means E. The workpiece W is placed on the stage 330, and plasma P is generated by introducing the microwave M into the chamber in a state where a predetermined gas is introduced through a gas introduction system (not shown). By this plasma, the gas is appropriately decomposed or activated, and active species such as radicals or decomposed species R act on the workpiece W. In this way, various plasma treatments such as etching, ashing, deposition, surface modification, and doping can be performed.

  According to the present invention, in such a plasma processing apparatus, by providing the microwave introducer described above with reference to FIGS. 1 to 6, the apparatus can be miniaturized and the microwave M can be introduced with high efficiency and stabilized. High density plasma P can be generated. Further, even when the process conditions change or fluctuate, the plasma can be stably generated and maintained by the effect of the transition region in which the effective dielectric constant decreases substantially continuously toward the plasma.

  In addition, as described above, the microwave M can be introduced with high efficiency even when the plasma density is high or low. That is, in this embodiment, the optimum dielectric constant of the waveguide surface can be obtained without fail depending on the plasma density.

  Inside the chamber 300, for example, the plasma ignition conditions and the maintenance conditions are often not necessarily the same due to, for example, the gas flow and pressure distribution, or the arrangement of internal structures. On the other hand, according to this embodiment, by providing a plurality of waveguides 100, plasma can be reliably ignited and stably maintained in any waveguide 100.

(Example)
Hereinafter, examples implemented by the present inventor will be described.
FIG. 9 is a schematic cross-sectional view showing a microwave introducer of a comparative example and an example of the present invention.
The microwave introducer of the comparative example shown in FIG. 9A includes a substantially cylindrical waveguide body 100 having an outer conductor 100a made of a dielectric and an inner conductor 100b made of a metal. However, the peripheral side surface is smooth, and the uneven part is not formed.

  On the other hand, the microwave introducer of the present embodiment shown in FIG. 9B also includes a substantially cylindrical waveguide body 100 having an outer conductor 100a made of a dielectric and an inner conductor 100b made of a metal. And the uneven | corrugated | grooved part 120 is formed in the surrounding side surface. Here, in both the comparative example shown in FIG. 9A and the present embodiment shown in FIG. 9B, the overall length L of the waveguide 100 is 500 millimeters, and the diameter D1 of the inner conductor 100b is 15 millimeters. The diameter D2 of the outer conductor 100a was 40 millimeters. In addition, the diameter D2 in a present Example was defined in the center of the convex surface and concave surface of the uneven | corrugated | grooved part 120, as represented to FIG.9 (b). Moreover, in the microwave introducer of the present embodiment shown in FIG. 9B, the pitch P1 of the uneven portions 120 was 8 millimeters, and the height H of the uneven portions 120 was 4 millimeters.

  The microwave introduction devices of these comparative examples and this example were respectively attached to the chamber 300, and plasma was generated by introducing 2.45 GHz microwaves while maintaining the pressure in the chamber at 40 Pascals. It was.

FIG. 10 is a graph showing the relationship between the electron density of plasma and the amount of reflection of microwaves. That is, the horizontal axis of the figure represents the electron density of the generated plasma, and the vertical axis represents the amount of microwave reflection in the microwave introducer.
From FIG. 10, it can be seen that when the microwave introducer of the comparative example is used, the amount of reflection of the microwave is generally high, and the amount of reflection increases as the electron density decreases. That is, it can be seen that the amount of reflected microwaves depends on the electron density.
On the other hand, when the microwave introducer of the present embodiment is used, it can be seen that the amount of reflected microwaves is at most 6 decibels lower than that of the comparative example, and is always low regardless of the electron density.

  That is, by providing the microwave introduction device with the concavo-convex portion 120, it is possible to suppress the reflection of the microwave and increase the amount of absorption of the microwave. In addition, the dependence of the amount of reflected microwaves on the plasma density is relaxed, and stable microwave absorption can be realized at any plasma density. As a result, the load is stabilized regardless of the plasma generation conditions, the discharge is stabilized under any discharge conditions, and stable plasma treatment is possible.

  The embodiments of the present invention have been described with reference to specific examples. However, the present invention is not limited to these specific examples.

  For example, the present invention is not limited to a reduced pressure plasma generator and a reduced pressure plasma processing apparatus that generate plasma in a reduced pressure space and perform plasma processing, and an atmospheric pressure plasma generator and atmospheric pressure that generate plasma in an atmospheric pressure space and perform plasma processing. Even if it is used in a plasma processing apparatus, the same effect can be obtained, and these are also included in the scope of the present invention.

  In addition, the waveguide 100, the waveguide 200, the chamber 300, and the elements attached to these used in the present invention are not limited to the shapes and sizes shown in the drawings, but the cross-sectional shape, wall thickness, and shape of the opening. The size, material, and the like can be appropriately changed within the scope of the present invention to obtain the same effects, and these are also included in the scope of the present invention.

  The waveguide does not need to be a perfect square, and the coaxial introduction part and the coaxial conversion part do not need to be completely cylindrical.

  Further, the shape and size of the chamber 300, or the arrangement relationship within the chamber 300 are not limited to those shown in the drawings, and can be appropriately determined in consideration of the contents and conditions of the plasma processing. For example, the plasma generating unit may be attached to the side surface or the lower surface instead of the upper surface of the plasma processing chamber, or a combination thereof may be used. That is, a plurality of plasma generation units may be provided in one chamber. This makes it possible to form a large-area plasma having a uniform or predetermined density distribution according to the shape and size of the object to be processed.

  Furthermore, in the above-described specific examples, only the main components of the plasma generator and the plasma processing apparatus have been described. However, the present invention includes all plasma processing apparatuses having such a plasma generator, for example, etching. Any plasma processing apparatus realized as an apparatus, an ashing apparatus, a thin film deposition apparatus, a surface treatment apparatus, a plasma doping apparatus, and the like is included in the scope of the present invention.

It is a conceptual diagram for demonstrating the principal part basic composition of the microwave introducer concerning the specific example of this invention. It is a graph which illustrates distribution of dielectric constant in the state where plasma was generated. It is a graph which illustrates distribution of dielectric constant (epsilon) _eff in a transition area _| region. It is a schematic diagram which illustrates the shape of the outer conductor 100a which can be used in this invention. It is a schematic diagram showing the other specific example of the outer conductor 100a which can be used in this invention. It is a schematic diagram showing the other specific example of the outer conductor 100a which can be used in invention. It is a conceptual diagram for demonstrating the principal part basic composition of the plasma processing apparatus concerning embodiment of this invention. 4 is a schematic plan view illustrating the arrangement of microwave introducers when viewed from above the chamber 300. FIG. It is a schematic cross section showing the microwave introducer of a comparative example and an example of the present invention. It is a graph showing the relationship between the electron density of plasma and the amount of reflection of microwaves. It is a conceptual diagram of the plasma processing apparatus provided with the waveguide body concerning a prior art.

Explanation of symbols

100 waveguide body, 100a outer conductor, 100b inner conductor, 110 waveguide root, 120 uneven portion, 200 waveguide, 300 chamber, 320 O-ring, 330 stage, M microwave, P plasma, R active species and decomposition seed

Claims (12)

A microwave introducer attached to a chamber having a space for generating plasma,
A waveguide projecting from the wall surface of the chamber toward the space for generating the plasma;
The waveguide includes an inner conductor made of a conductor and extending in one direction, and an outer conductor made of a dielectric and covering the inner conductor.
A microwave introducer having a concavo-convex portion that affects an effective dielectric constant of the outer conductor formed on a surface of the outer conductor.   The microwave introducer according to claim 1, wherein the central axis of the inner conductor and the central axis of the outer conductor are substantially coaxial.   3. The microwave introducer according to claim 1, wherein the uneven portion has a plurality of protrusions having a substantially rectangular cross section.   The said uneven | corrugated | grooved part has a some protrusion body which forms the transition area | region where the effective dielectric constant falls substantially continuously toward the said plasma between the said plasma. The microwave introducer described.   5. The microwave introducer according to claim 4, wherein the transition region is a region in which a filling factor of the dielectric decreases substantially continuously toward the plasma.   6. The microwave introducer according to claim 4, wherein the transition region includes a dielectric having a cross section whose tip is focused toward the plasma.   3. The microwave introducer according to claim 1, wherein the concavo-convex portion has a plurality of protrusions made of a dielectric material whose tips are focused toward the plasma.   3. The microwave introducer according to claim 1, wherein the uneven portion has a plurality of holes whose tips converge toward the waveguide. 4. A chamber;
The microwave introducer according to any one of claims 1 to 8, attached to the chamber;
With
A plasma generating apparatus characterized in that plasma can be generated in a space in which the plasma is generated by a microwave introduced through the waveguide.   The plasma generating apparatus according to claim 9, further comprising a waveguide provided outside the chamber and introducing a microwave into the waveguide.   The plasma generating apparatus according to claim 10, wherein the central axis of the waveguide and the central axis of the waveguide are substantially coaxial. A plasma generator according to any one of claims 9 to 11, comprising:
A plasma processing apparatus characterized in that plasma processing of an object to be processed can be performed by the generated plasma.

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