Plasma treatment apparatus and plasma treatment method

Abstract

[Problem] To minimize the circumferential non-uniformity of microwave electric field intensity in the outer periphery of a wafer and improve the circumferential uniformity of plasma processing. [Solution] TE11 mode microwaves are coaxially guided into a plasma processing apparatus within the processing chamber via a circular waveguide. A 90˚ phase retardation plate is positioned above the microwaves within the circular waveguide, and a 180˚ phase retardation plate is positioned below it. A rotation drive mechanism is connected to the 180˚ phase retardation plate within the plasma processing apparatus. A detector for detecting circumferential electric field intensity non-uniformity is connected below the 180˚ phase retardation plate within the plasma processing apparatus. A control means is provided to adjust the rotation angle of the 180˚ phase retardation plate in a manner that minimizes the deterioration of the axisymmetricality of the electric field intensity detected by the detector.

Description

Plasma Processing Apparatus and Plasma Processing Method The present invention relates to a plasma processing apparatus and a plasma processing method for processing a substrate sample such as a semiconductor wafer disposed in a processing chamber formed in a vacuum chamber using plasma, such as etching. The structure of semiconductor elements is continuously miniaturized or complicated to achieve both improved computing power and low power consumption. As a result of the required complexity of the manufacturing process or high-difficulty processing, the manufacturing cost of semiconductor elements has become high. To reduce the manufacturing cost, it is desired to increase the number of high-quality semiconductor elements manufactured from one semiconductor wafer (hereinafter also referred to as a unit or a wafer) to improve mass productivity. To increase the number of semiconductor elements obtained from one wafer, it is necessary to ensure good process uniformity within the wafer surface. In particular, since a large number of semiconductor elements can be obtained in the outer peripheral portion of the wafer, it is extremely important to ensure good process uniformity in the circumferential direction for uniform processing in the outer peripheral portion of the wafer. Plasma processing such as plasma etching, plasma CVD (Chemical Vapor Deposition), and plasma ashing is widely used in semiconductor element manufacturing. In the generation of plasma, various methods such as ICP (Inductively Coupled Plasma), CCP (Capacitively Coupled Plasma), ECR (Electron Cyclotron Resonance), and surface wave-excited plasma are known, either as a method of applying a DC voltage between electrodes or as a method of generating plasma using high-frequency power. In a plasma processing apparatus using microwaves, in order to generate plasma that is uniform in the circumferential direction with respect to the central axis of the wafer, microwaves are mostly introduced from the direction of the central axis of the wafer to be processed toward the surface to be processed of the wafer to be processed. However, depending on the mode of propagation of microwaves in the waveguide, the electric field distribution is not necessarily axisymmetric. For example, in the fundamental mode of microwaves propagating inside a circular waveguide, that is, the TE11 mode, the electric field distribution of the microwaves is non-axisymmetric. In order to form the electric field distribution into an axisymmetric shape in the above-described case, it is effective to rotate the polarization plane to form circularly polarized waves. In the configuration of Patent Document 1, there is a configuration in which a microwave rotation generator (dielectric plate) is provided inside a circular waveguide in order to form the electric field distribution inside the circular waveguide into an axisymmetric shape. Patent Document 2 shows a structure having a plurality of stubs inside a circular waveguide and controlling the insertion amount of the stubs. The axisymmetry of the electric field distribution inside the circular waveguide can be improved by the insertion amount of the stubs. By adjusting the insertion amount of the stubs, the axisymmetry of the electric field distribution can be ensured. [Prior Art Documents] [Patent Documents] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-50046 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-110312 [Non-Patent Document] [Non-Patent Document 1] Microwave Circuits (co-authored by Kunihiro Suemugi and Shuuichi Hayashi, Ohmsha, Ltd., 1958) (Problems to be Solved by the Invention) In a plasma processing apparatus that generates plasma using a high-frequency electric field such as microwaves, as described in Patent Document 1 or Non-Patent Document 1, as a means for forming circularly polarized waves, a microwave rotary generator or a 90-degree phase difference plate made of a dielectric plate is shown. In this method, if the reflected wave from the outlet of the waveguide is small, an axially symmetric electric field distribution can be expected. However, if the reflected wave returning from the inside of the processing chamber is large, the direction of the electric field vibration of the microwave incident on the microwave rotary generator or the 90-degree phase difference plate deviates from the direction assumed at the time of design, and the axial symmetry of the electric field distribution may be lost. For example, in a plasma processing apparatus, there is a case where microwaves are not completely absorbed by the plasma and return to the waveguide depending on the conditions used during processing. In order to ensure the axial symmetry of the electric field distribution under various discharge conditions, it is necessary to dynamically control the electric field distribution. As a means for dynamic control, there is the method using a stub described in Patent Document 2. Regarding the problem of the method of changing the insertion amount of the stub, it is necessary to list a driving mechanism depending on the number of stubs, and the control method is complicated. In addition, if a stub or a driving mechanism is provided, at least the length of the stub causes the structure to protrude outside the circular waveguide, and an increase in the footprint of the apparatus is also a problem. An object of the present invention is to provide a technique for minimizing the circumferential non-uniformity of the microwave electric field intensity and improving the circumferential uniformity of plasma processing in the outer peripheral portion of a wafer. Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. (Means for Solving the Problems) If the outline of a representative example of the present invention is briefly described, it is as follows. According to one embodiment, in a plasma processing apparatus in which microwaves in the TE11 mode are introduced into a processing chamber through a circular waveguide coaxially, a 90° phase difference plate for microwaves is provided above the inside of the circular waveguide, and a 180° phase difference plate is provided below it. In addition, a rotary drive mechanism is connected to the 180° phase difference plate. Further, a detector (measurement means) for detecting the non-uniformity of the electric field intensity in the circumferential direction is connected below the 180° phase difference plate, and there is a control means for adjusting the rotation angle of the 180° phase difference plate in such a manner as to minimize the deterioration of the axial symmetry of the electric field intensity detected by the detector. (Effects of the Invention) In the outer peripheral portion of the wafer, the circumferential non-uniformity of the microwave electric field intensity is minimized, and the circumferential uniformity of plasma processing is improved. Thereby, the number of high-quality semiconductor elements manufactured from one semiconductor wafer can be increased, and thus the mass productivity of semiconductor elements can be improved. Embodiments of the present invention will be described below with reference to the drawings. However, in the following description, the same reference numerals are assigned to the same components and repeated description is omitted. Among them, the drawings are schematically shown for the purpose of making the description clearer, and are different from the actual aspect. This is only an example and is not intended to limit the interpretation of the present invention. [Embodiment 1] A cross-sectional view of an etching apparatus according to a first embodiment of the present invention is shown in FIG. 1. In the etching apparatus shown in FIG. 1, that is, the plasma processing apparatus 100, microwaves are oscillated by a microwave source 1, and are transmitted through an isolator 2, an automatic integrator 3, and a rectangular waveguide 4 to a circular waveguide 5 through a circular-rectangular converter 6. In this embodiment, microwaves of 2.45 GHz, which are commonly used industrially, are used. The isolator 2 is used to protect the microwave source 1 from the influence of reflected microwaves. The automatic integrator 3 is used to adjust the load impedance and suppress the reflected waves to efficiently supply microwaves. In order to easily handle the propagation phenomenon of microwaves, the rectangular waveguide 4 is configured to propagate only in the fundamental mode TE10 mode, and the circular waveguide 5 is configured to propagate only in the fundamental mode TE11 mode, and the dimensions of the waveguide cross-section are specified. In the circular waveguide 5, a 90-degree phase difference plate 7 and a 180-degree phase difference plate 9 connected to a rotation drive mechanism 8 are provided. The microwaves introduced into the circular waveguide 5 are propagated to the 90° phase difference plate 7, the 180° phase difference plate 9, and the cavity portion 10, and are introduced into a substantially cylindrical plasma processing chamber 13 (also referred to as a processing container) through a microwave introduction window 11 and a shower plate 12. The circular waveguide 5 is arranged to be axially symmetric with respect to the plasma processing chamber 13. The cavity portion 10 uses a conductor as a material for reflecting microwaves. As the material of the cavity portion 10, for example, aluminum is used. An inner cylinder 14 is provided inside the side wall of the plasma processing chamber 13 to protect the side wall of the plasma processing chamber 13 from the influence of plasma. The inner cylinder 14 located near the plasma uses quartz as a material with high plasma resistance. Alternatively, as a material with high plasma resistance, yttrium oxide, aluminum oxide, yttrium trifluoride, aluminum fluoride, aluminum nitride, etc. can also be used. As the materials of the microwave introduction window 11 and the shower plate 12, quartz is used as a material for transmitting microwaves. Alternatively, if it is a material for transmitting microwaves, other dielectric materials can also be used. Alternatively, as a material with high plasma resistance, yttrium oxide, aluminum oxide, yttrium trifluoride, aluminum fluoride, aluminum nitride, etc. can also be used. Gas is supplied by a gas supply means 15 between the microwave introduction window 11 and the shower plate 12. The gas supply means 15 includes a function of supplying a desired flow rate by a mass flow controller. In addition, the type of gas used is appropriately selected according to the film to be processed, etc., and a plurality of gas types are supplied in combination at a predetermined flow rate. A plurality of gas supply holes are provided in the shower plate 12, and the gas is supplied to the plasma processing chamber 13 through the gas supply holes. The supplied gas is evacuated by a turbomolecular pump 17 through a conductance control valve 16. At the lower part of the plasma processing chamber 13, a substrate stage and high-frequency electrode 19 for placing the substrate to be processed 18 is provided, and an insulating plate 29 is provided below it. The substrate stage and high-frequency electrode 19 is supplied with bias power by a bias power supply 20 through an automatic matcher 21. The substrate to be processed 18 is a semiconductor wafer as a substrate sample. The central axis of the circular waveguide 5 coincides with the central axis of the plasma processing chamber 13. In addition, the central axis of the plasma processing chamber 13 coincides with the central axis of the substrate stage and high-frequency electrode 19, and is arranged axially symmetrically so as to coincide with the central axis of the semiconductor wafer placed on the substrate stage and high-frequency electrode 19. The bias power is adjusted to control the energy of the ions incident on the substrate to be processed 18 so as to perform a desired etching. The substrate stage and high-frequency electrode 19 is equipped with an adsorption mechanism for the substrate to be processed 18 (not shown) and a temperature control means, and the temperature of the substrate to be processed 18 is adjusted as needed so as to perform a desired etching. In order to protect the outer peripheral portion of the substrate stage and high-frequency electrode 19 from plasma influence, a base 22 and a stage cover 23 are provided. Quartz is used as the material with high plasma resistance for the base 22 and the stage cover 23. The etching is performed by irradiating the ions or radicals generated there onto the substrate to be processed 18 by generating plasma 24 in the plasma processing chamber 13 by the microwave supplied from the microwave source 1. Next, the detailed structure inside the circular waveguide 5 and its effects will be described. First, the detailed structure of the 90° phase difference plate 7 will be described using FIG. 2. FIG. 2 is a top cross-sectional view of the circular waveguide 5 and the 90° phase difference plate 7. Consider the case where a microwave in the TE11 mode is introduced in the y-axis direction in the figure with the electric field vibration direction 30 and propagates from the front surface of the paper toward the back. The 90° phase difference plate 7 is provided at an angle of rotating the vibration direction of the electric field by 45°. Here, the y'-axis is defined as the axis in the direction of the 90° phase difference plate 7, and the x'-axis is defined as the axis perpendicular to the y'-axis. The 90° phase difference plate 7 uses quartz as the dielectric material for transmitting microwaves. Fig. 3 shows a diagram representing the effect of a 90° phase difference plate. (A) of Fig. 3 is a cross-sectional view of a circular waveguide in the x'-z plane, and (B) of Fig. 3 is a cross-sectional view of a circular waveguide in the y'-z plane. In (A) and (B) of Fig. 3, the curves in the circular waveguide 5 represent waves. In (A) of Fig. 3, a wave having an amplitude in the x' direction is shown, and in (B) of Fig. 3, a wave having an amplitude in the y' direction is shown. A microwave having an amplitude in the y-axis direction can be expressed as a superposition of waves introduced with equal amplitudes and in the same phase in the x' direction and the y' direction. When the microwave passes through the 90° phase difference plate 7, the phase difference between the wave having an amplitude in the x' direction and the wave having an amplitude in the y' direction becomes 90°. This is because the phase of the wave having an amplitude in the y' direction is delayed by 90° when passing through the 90° phase difference plate 7. As a result, it means that circularly polarized light is formed. Here, the height H of the 90° phase difference plate 7 1 must be set to an appropriate value such that the phase difference between the wave of the x' component and the wave of the y' component becomes 90°. The height H of the 90° phase difference plate 7 1 becomes the following formula (1). Here, λg represents the in-tube wavelength of the microwave in a circular waveguide in vacuum, and ε r is the dielectric constant of the 90° phase difference plate 7. For example, when the microwave is at a frequency of 2.45 GHz, the in-tube wavelength is 203 mm. If the dielectric constant of quartz is set to 3.8, H 1 becomes 53.5 mm. As described above, if there is no reflection from the plasma, by using the 90° phase difference plate 7, circularly polarized light can be formed, and microwaves can be uniformly introduced in the circumferential direction. In this embodiment, a rectangular parallelepiped-shaped phase difference plate is shown as the 90° phase difference plate 7, but it is not necessarily a rectangular parallelepiped shape for the purpose of forming a 90° phase difference. In addition, the 90° phase difference plate 7 has a microwave reflection portion at its end face, and there is a case where the angular deviation for forming a 90° phase difference is 45°. That is, the angle at which the 90° phase difference plate 7 is provided is not limited to an angle of 45° relative to the electric field vibration direction, and is appropriately set to the optimum angle according to the microwave reflection coefficient of the 90° phase difference plate 7. As shown in this embodiment, when the 90° phase difference plate 7 is set to be rotated counterclockwise by 45° relative to the vibration direction of the electric field (refer to Fig. 2), a counterclockwise circularly polarized wave is formed. Next, with reference to FIG. 4, the detailed structure of the 180° phase difference plate 9 connected to the rotary drive mechanism 8 will be described. FIG. 4 is a top sectional view of the circular waveguide in the peripheral portion of the 180° phase difference plate 9. The circular waveguide 5 is formed in a double-layer structure (5-1, 5-2), and is composed of an inner waveguide 5-1 and an outer waveguide 5-2 covering the outer periphery thereof. The inner waveguide 5-1 supports the 180° phase difference plate 9, and the inner waveguide 5-1 and the 180° phase difference plate 9 are integrally formed and can be rotated in the θ direction by the actuator 25 of the rotary drive mechanism 8. In addition, the rotation angle of the 180° phase difference plate 9 is monitored at any time by an encoder (not shown). As the material of the 180° phase difference plate 9, for example, quartz is used as the material for transmitting microwaves. For example, the actuator 25 of the rotary drive mechanism 8 is an electromagnetic motor, and is formed in a structure where the connection portion with the inner waveguide 5-1 is a gear or a belt. Alternatively, the actuator 25 may also be an ultrasonic motor. As shown in FIG. 4, the 180° phase difference plate 9 is inserted at an angle of θ with respect to the x-axis. Here, the axis in the θ direction is defined as the x” axis, and the axis perpendicular to the x” axis is defined as the y” axis. With reference to FIG. 5, the effect when the counterclockwise circularly polarized wave generated by the 90° phase difference plate 7 is incident on the 180° phase difference plate 9 will be described. FIG. 5(A) is a sectional view of the circular waveguide in the y”-z plane, and FIG. 5(B) is a sectional view of the circular waveguide in the x”-z plane. As a result of the microwave having an amplitude in the x” axis being delayed by 180°, at the exit of the 180° phase difference plate 9, a 180° phase difference occurs between the wave in the x” component and the wave in the y” component. The incident wave on the 180° phase difference plate 9 is a circularly polarized wave having a 90° phase difference. Therefore, as a result, the phase difference between the waves having an electric field component in the x” axis and the y” axis becomes 90° + 180° = 270°. This means that it is converted into a clockwise circularly polarized wave. The height H of the 180° phase difference plate 2 must be set to an appropriate value such that the phase difference between the wave in the x” component and the wave in the y” component becomes 180°. The height H of the 180° phase difference plate 9 2 becomes the following formula (2). The 180° phase difference plate 9 has the effect of reversing the polarization direction of the circularly polarized wave. In addition, FIG. 6 is used to illustrate that the 180° retardation plate 9 has the effect of rotating the polarization plane of linearly polarized light. As shown in FIG. 6, consider the case where the insertion direction of the 180° retardation plate 9 is set as the x-axis, and linearly polarized light with an electric field vibration direction 34 in the direction at an angle α with respect to the x-axis is incident. At this time, due to the 180° retardation plate 9, the phase of the wave component in the x-axis direction is delayed, and thus the microwave that has passed through the 180° retardation plate 9 is converted into linearly polarized light with an electric field vibration direction 35 in the direction at an angle -α with respect to the x-axis. That is to say, if the rotation angle of the 180° retardation plate 9 is adjusted, the angle of the polarization plane of linearly polarized light can be adjusted. As described above, the 180° retardation plate 9 has the effect of reversing the rotation direction of the incident circularly polarized light. In addition, the 180° retardation plate 9 has the effect of rotating the polarization plane of the incident linearly polarized light. If there is no reflected wave from the outlet of the circular waveguide 5, the linearly polarized light incident on the 90° retardation plate 7 is converted into counterclockwise circularly polarized light, and is converted into clockwise circularly polarized light by the 180° retardation plate 9. Next, FIG. 7 is used to illustrate the case where there is a reflected wave from the outlet of the circular waveguide 5. FIG. 7 is an enlarged cross-sectional view from the automatic integrator 3 to the outlet of the circular waveguide 5. If there is a reflected wave, it is assumed, for example, that the microwave supplied to the plasma processing chamber 13 is reflected without being absorbed by the plasma 24 or is reflected by the wall surface of the plasma processing chamber 13. The reflected wave RW (RWx: x-axis component of the reflected wave RW, RWy: y-axis component of the reflected wave RW) propagates along a path opposite to the incident wave through the circular waveguide 5, the 180-degree retardation plate 9, the 90-degree retardation plate 7, the circular-rectangular converter 6. The microwave electric field in the circular waveguide 5 can be represented by the superposition of waves in the TE11 mode having electric field vibration directions in independent two axes (the x and y axes in FIG. 7). On the other hand, the rectangular waveguide 4 has an electric field vibration direction in one axis (the z axis in FIG. 7) corresponding to the TE10 mode. That is, in the process of the wave propagating in the circular waveguide 5 reaching the rectangular waveguide 4, the degree of freedom of one electric field vibration direction is lost. The TE11 mode with an electric field vibration direction in the y-axis direction corresponds to the electric field vibration direction 40 of the TE10 mode of the rectangular waveguide 4, so it can propagate toward the automatic integrator 3. On the other hand, the electromagnetic wave in the TE11 mode with an electric field vibration direction in the x-axis direction in the circular waveguide 5 cannot propagate in the rectangular part of the circular-rectangular converter 6 and is reflected, and then re-incident on the 90-degree retardation plate 7. That is, the microwave incident on the 90° retardation plate 7 is the sum of the wave in the TE11 mode with an electric field vibration direction in the y-axis direction and the reflected wave RW (RWx) in the circular-rectangular converter 6. As a result, when the reflected wave RW is incident from the outlet of the circular waveguide 5, the axial symmetry of the circularly polarized light is lost in the 90-degree retardation plate 7. As described above, the rotation angle of the 180-degree retardation plate 9 can be used to adjust the angle of the polarization plane of linearly polarized waves, and thus the angle of the polarization plane of the microwave reflected again by the circular-rectangular converter 6 can be adjusted. That is, by controlling the polarization plane of the wave incident on the 90-degree retardation plate 7, as a result, the circumferential direction non-uniformity of the electric field can be minimized. For example, if the 180-degree retardation plate 9 is rotated during plasma processing, the circumferential direction non-uniformity of the time-averaged electric field can be minimized. Alternatively, according to the processing conditions used in plasma processing, the 180-degree retardation plate 9 is adjusted to the optimum angle, whereby the circumferential direction non-uniformity of the electric field can be reduced. In order to control to the optimum angle, it is necessary to measure the circumferential direction non-uniformity of the electric field. As an indirect measurement method, for example, the reflection coefficient and its phase of the load can also be monitored in the microwave automatic integrator 3, the reflection coefficient at the outlet of the circular waveguide 5 can be estimated, and the rotation angle of the 180-degree retardation plate can be adjusted according to the reflection coefficient. As a direct measurement method, an electric field measurement means can also be provided in the circular waveguide 5. By the plasma processing apparatus or plasma processing method of Example 1, the circumferential direction non-uniformity of the microwave electric field intensity can be minimized in the outer peripheral portion of the wafer, and the circumferential direction uniformity of plasma processing can be improved. Thereby, the number of high-quality semiconductor elements manufactured from one semiconductor wafer can be increased, and thus the mass productivity of semiconductor elements can be improved. [Example 2] FIG. 8 shows a cross-sectional view of a plasma processing apparatus (etching apparatus) according to a second embodiment of the present invention. FIG. 8 is a cross-sectional view of a plasma processing apparatus 100a provided with a circular polarization detector 26. As shown in FIG. 8, the circular polarization detector 26 is provided on the downstream side of the 180-degree retardation plate 9 (the outlet side of the circular waveguide 5). By monitoring the state of circular polarization by the circular polarization detector 26, the optimum angle of the 180-degree retardation plate 9 can be controlled thereby. The circular polarization detector 26 can be regarded as a measurement means for measuring the circumferential electric field in the circular waveguide 5. Using FIG. 9, a specific example of the circular polarization detector 26 will be described. To configure the circular polarization detector 26, electric field probes 27 are provided at a plurality of locations on the circular waveguide 5, and the circumferential direction non-uniformity of the electric field is monitored by relatively comparing the electric fields measured and detected by the plurality of electric field probes 27. As the electric field probe 27, for example, a crystal detector is used. The electric field probes 27 are provided at at least three or more locations on the circumference of the circular waveguide 5. In addition, in order to detect circular polarization, the positions of the individual electric field probes 27 must not form positions that are line-symmetric. The measured values of the electric field probes 27 are input to the control unit (also referred to as control means) 28 for arithmetic processing. The control unit 28 transmits a control signal for controlling the rotation angle of the 180° phase difference plate 9 to the rotation drive mechanism 8 based on the arithmetic processing. Thereby, the control unit 28 controls the rotation angle of the 180° phase difference plate 9 and minimizes the circumferential direction non-uniformity of the electric field. In addition, in the plasma processing method of the plasma processing apparatus using FIGS. 8 and 9, the angle of the 180-degree phase difference plate 9 is adjusted by the control unit 28 in such a manner that the circumferential direction non-uniformity of the electric field measured by the circular polarization detector 26 (or the electric field probe 27) as the measurement means is minimized. By the plasma processing apparatus or plasma processing method of Example 2, the same effects as those of Example 1 can also be obtained. The invention completed by the present inventors has been specifically described above based on the embodiments. However, it goes without saying that the present invention is not limited to the above-described embodiments and examples, and various modifications can be made. (Industrial Applicability) The present invention is applicable to a plasma processing apparatus for processing a sample on a substrate such as a semiconductor wafer by etching or the like. 1: Microwave source 2: Isolator 3: Automatic integrator 4: Rectangular waveguide 5: Circular waveguide 5-1: Inner waveguide 5-2: Outer waveguide 6: Circular-rectangular converter 7: 90° phase difference plate 8: Rotation drive mechanism 9: 180° phase difference plate 10: Cavity 11: Microwave introduction window 12: Shower plate 13: Plasma processing chamber 14: Inner cylinder 15: Gas supply means 16: Conductance control valve 17: Turbomolecular pump 18: Substrate to be processed 19: Substrate stage and high-frequency electrode 20: Bias power supply 21: Automatic integrator 22: Base 23: Stage cover 24: Plasma 25: Actuator 26: Circular polarization detector 27: Electric field probe 28: Control unit 29: Insulating plate 30: Electric field vibration direction of TE11 mode 34: Vibration direction of the electric field of the microwave incident on the 180° phase difference plate 35: Vibration direction of the electric field of the microwave passing through the 180° phase difference plate 40: Electric field vibration direction of TE10 mode 100, 100a: Plasma processing apparatus (etching apparatus) H 1: Height H of the 90° retardation plate 7 2 : Height RW of the 180° retardation plate 9: Reflected wave RWx: x-axis component of the reflected wave RW RWy: y-axis component of the reflected wave RW [Fig. 1] is a cross-sectional view of an etching apparatus according to a first embodiment of the present invention. [Fig. 2] is a cross-sectional view of a 90° retardation plate and a circular waveguide. [Fig. 3] is a diagram showing the effect of the 90° retardation plate. [Fig. 4] is a cross-sectional view of a 180° retardation plate and a circular waveguide. [Fig. 5] is a diagram showing the effect of the 180° retardation plate. [Fig. 6] is a diagram showing the effect of the 180° retardation plate. [Fig. 7] is an enlarged cross-sectional view from the automatic integrator to the circular waveguide. [Fig. 8] is a cross-sectional view of a plasma processing apparatus provided with a circular polarization detector according to a second embodiment of the present invention. [Fig. 9] is an enlarged cross-sectional view of the circular polarization detector. 1: Microwave source 2: Isolator 3: Automatic integrator 4: Rectangular waveguide 5: Circular waveguide 6: Circular-rectangular converter 7: 90° retardation plate 8: Rotation drive mechanism 9: 180° retardation plate 10: Cavity 11: Microwave introduction window 12: Shower plate 13: Plasma processing chamber 14: Inner cylinder 15: Gas supply means 16: Conductance regulating valve 17: Turbomolecular pump 18: Substrate to be processed 19: Substrate stage and high-frequency electrode 20: Bias power supply 21: Automatic integrator 22: Base 23: Stage cover 24: Plasma 29: Insulating plate 100: Plasma processing apparatus (etching apparatus)

Claims

1. A plasma processing apparatus, characterized in that: it comprises: a generally cylindrical processing container, which is supplied with high-frequency power of microwaves through an integrator, a rectangular waveguide, and a circular waveguide, wherein a 90-degree phase retardation plate and a 180-degree phase retardation plate are disposed in the aforementioned circular waveguide; and further comprises: a measuring means for measuring the circumferential electric field within the aforementioned circular waveguide and disposed at the lower part of the aforementioned 180-degree phase retardation plate.

2. The plasma treatment apparatus as claimed in claim 1, wherein, A rotary drive mechanism is connected to the aforementioned 180-degree phase difference plate.

3. The plasma treatment apparatus as claimed in claim 1, wherein, Additionally, it includes a control means that adjusts the angle of the aforementioned 180-degree phase difference plate in a manner that minimizes the circumferential non-uniformity of the electric field measured by the aforementioned measurement means.

4. A plasma treatment method using the plasma treatment apparatus of claim 1, characterized in that: the angle of the aforementioned 180-degree phase difference plate is adjusted in a manner that minimizes the circumferential non-uniformity of the electric field measured by the aforementioned measuring means.

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