JP6117763B2 - Plasma processing equipment - Google Patents

Description

  Various aspects and embodiments of the present invention relate to a plasma processing apparatus.

  In semiconductor manufacturing processes, plasma processing for the purpose of thin film deposition or etching is widely performed. In order to obtain a high-performance and high-performance semiconductor, it is required to perform uniform plasma treatment on the entire surface to be processed of the substrate to be processed.

  In recent plasma processing, a plasma processing apparatus that generates plasma using a microwave is used. Such a plasma processing apparatus includes a slot plate in which a plurality of slots are arranged in the circumferential direction, and a slow wave plate provided on the slot plate. The slot plate radiates microwaves for generating plasma from a plurality of slots. Microwaves radiated from a plurality of slots of the slot plate are guided to the plasma processing space by a dielectric provided between the slot plate and the plasma processing space in the processing container. The slow wave plate supplies microwaves to each of the plurality of slots of the slot plate.

  By the way, in such a plasma processing apparatus, in order to perform uniform plasma processing on the entire surface to be processed of the substrate to be processed, it is required to suppress the deviation of the electric field strength in the slow wave plate. In this regard, the microwave propagating in the slow wave plate along the radial direction of the slot plate is reflected to the center side of the slow wave plate by the unevenness formed on the outer periphery of the slow wave plate, and the reflected waves of the microwaves are canceled out. There is a conventional technique to make it. By offsetting the reflected waves of the microwaves propagating in the slow wave plate along the radial direction of the slot plate, the bias of the electric field strength in the slow wave plate along the radial direction of the slot plate is improved.

Japanese Patent No. 4554065

  However, in the above-described prior art, the circumferential direction of the slot plate generated in the slow wave plate due to the reflected wave of the microwave returning from the plurality of slots arranged along the circumferential direction of the slot plate to the slow wave plate It is not taken into consideration to suppress the deviation of the electric field strength along the line.

  That is, it is known that the reflected wave of the microwave returning from the plurality of slots arranged along the circumferential direction of the slot plate to the slow wave plate propagates not only in the radial direction of the slot plate but also in the circumferential direction of the slot plate. ing. However, as in the prior art, only by canceling the reflected waves of the microwaves propagating in the slow wave plate along the radial direction of the slot plate, it propagates in the slow wave plate along the circumferential direction of the slot plate. Since microwave reflected waves remain, the remaining reflected waves interfere with each other. As a result, there is a risk that the deviation of the electric field strength along the circumferential direction of the slot plate that occurs in the slow wave plate increases.

  In one embodiment, the disclosed plasma processing apparatus includes a processing container defining a processing space, a dielectric having a facing surface facing the processing space, and a surface of the dielectric opposite to the facing surface. A slot plate provided above, wherein a plurality of slots for radiating microwaves for generating plasma to the processing space via the dielectric are arranged along the circumferential direction about the axis. A slow wave plate provided on the slot plate, extending radially in the radial direction of the slot plate around the axis so as to cover the plurality of slots, and to each of the plurality of slots And a retardation plate having a plurality of extending portions for supplying waves.

  According to one aspect of the disclosed plasma processing apparatus, the microwave is generated in the retardation plate due to the reflected waves of the microwaves returning from the plurality of slots arranged along the circumferential direction of the slot plate to the retardation plate. There is an effect that the deviation of the electric field strength along the circumferential direction of the slot plate can be suppressed.

FIG. 1 is a diagram schematically illustrating a plasma processing apparatus according to an embodiment. FIG. 2 is a plan view of the slot plate according to the embodiment as viewed from the direction of the axis X. FIG. 3 is a perspective view showing a state in which the slow wave plate and the slot plate are combined in one embodiment. FIG. 4 is a diagram showing a distribution of electric field strength in the slow wave plate in one embodiment.

  In one embodiment, the disclosed plasma processing apparatus is provided on a processing container defining a processing space, a dielectric having a facing surface facing the processing space, and a surface opposite to the facing surface of the dielectric. A slot plate in which a plurality of slots for radiating microwaves for generating plasma to a processing space via a dielectric are arranged along the circumferential direction about the axis, and the slot plate And a plurality of extending portions that extend radially in the radial direction of the slot plate so as to cover the plurality of slots and supply microwaves to each of the plurality of slots. With a slow wave plate.

  In one embodiment of the disclosed plasma processing apparatus, a shielding member that shields microwaves is disposed in a space sandwiched between extension portions adjacent to each other among a plurality of extension portions.

  In one embodiment, the disclosed plasma processing apparatus further includes a cooling jacket provided on the retardation plate, and the shielding member is disposed in the space by being attached to the cooling jacket.

  In one embodiment of the disclosed plasma processing apparatus, the shielding member is disposed in the space by being attached to the slot plate.

  In one embodiment of the disclosed plasma processing apparatus, the width of each of the plurality of extending portions is set in a range of 1/2 to 1 times the wavelength of the microwave propagating through the slow wave plate. Is done.

  Moreover, in one embodiment of the disclosed plasma processing apparatus, the thickness of each of the plurality of extending portions is shorter than the width of each of the plurality of extending portions.

  In addition, the thickness of each of the plurality of extending portions is set to a length less than ½ times the wavelength of the microwave propagating through the slow wave plate.

  Hereinafter, various embodiments will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

  FIG. 1 is a diagram schematically illustrating a plasma processing apparatus according to an embodiment. The plasma processing apparatus 10 shown in FIG. 1 includes a processing container 12, a stage 14, a microwave generator 16, an antenna 18, and a dielectric window 20.

  The processing container 12 defines a processing space S for performing plasma processing. The processing container 12 has a side wall 12a and a bottom 12b. The side wall 12a is formed in a substantially cylindrical shape. Hereinafter, the axial line X extending in the cylindrical shape at the cylindrical center of the side wall 12a is virtually set, and the extending direction of the axial line X is referred to as the axial X direction. The bottom 12b is provided on the lower end side of the side wall 12a and covers the bottom opening of the side wall 12a. The bottom 12b is provided with an exhaust hole 12h for exhaust. The upper end of the side wall 12a is open.

  The upper end opening of the side wall 12 a is closed by the dielectric window 20. An O-ring 21 is interposed between the dielectric window 20 and the upper end portion of the side wall 12a. The dielectric window 20 is provided at the upper end portion of the side wall 12 a via the O-ring 21. The O-ring 21 makes the sealing of the processing container 12 more reliable. The stage 14 is accommodated in the processing space S, and the substrate W to be processed is placed thereon. The dielectric window 20 has a facing surface 20 a that faces the processing space S.

  The microwave generator 16 generates a microwave of 2.45 GHz, for example. In one embodiment, the plasma processing apparatus 10 further includes a tuner 22, a waveguide 24, a mode converter 26, and a coaxial waveguide 28.

  The microwave generator 16 is connected to the waveguide 24 via the tuner 22. The waveguide 24 is, for example, a rectangular waveguide. The waveguide 24 is connected to a mode converter 26, and the mode converter 26 is connected to the upper end of the coaxial waveguide 28.

  The coaxial waveguide 28 extends along the axis X. The coaxial waveguide 28 includes an outer conductor 28a and an inner conductor 28b. The outer conductor 28a has a substantially cylindrical shape extending in the axis X direction. The inner conductor 28b is provided inside the outer conductor 28a. The inner conductor 28b has a substantially cylindrical shape extending along the axis X.

  The microwave generated by the microwave generator 16 is guided to the mode converter 26 via the tuner 22 and the waveguide 24. The mode converter 26 converts a microwave mode and supplies the microwave after the mode conversion to the coaxial waveguide 28. Microwaves from the coaxial waveguide 28 are supplied to the antenna 18.

  The antenna 18 radiates a microwave for generating plasma based on the microwave generated by the microwave generator 16. The antenna 18 includes a slot plate 30, a slow wave plate 32, and a cooling jacket 34. The antenna 18 is provided on a surface 20 b opposite to the facing surface 20 a of the dielectric window 20, and radiates a microwave for generating plasma into the processing space S through the dielectric window 20.

  The slot plate 30 is formed in a substantially disc shape whose plate surface is orthogonal to the axis X. The slot plate 30 is disposed on the surface 20b opposite to the opposing surface 20a of the dielectric window 20 so that the plate surfaces of the dielectric window 20 and the dielectric plate 20 are aligned with each other. FIG. 2 is a plan view of the slot plate according to the embodiment as viewed from the direction of the axis X. In one embodiment, as shown in FIG. 2, the slot plate 30 is a slot plate constituting a radial line slot antenna. The slot plate 30 is formed in a metal disk shape having conductivity. In the slot plate 30, a plurality of slots 30 a are arranged along the circumferential direction about the axis X. The plurality of slots 30 a are slit-like holes that radiate microwaves to the processing space S through the dielectric window 20. In addition, a through hole 30 d through which a conduit 36 described later can pass is formed in the center portion of the slot plate 30.

  2 shows an example in which the plurality of slots 30a are formed as slit-like holes, the shape of the plurality of slots 30a is not limited to this. For example, the shape of the plurality of slots 30a may be circular, or may be a shape obtained by combining long holes extending in directions intersecting each other.

  Please refer to FIG. 1 again. The slow wave plate 32 is provided on the slot plate 30. The slow wave plate 32 is formed of a dielectric such as quartz, and supplies microwaves to the plurality of slots 30 a of the slot plate 30. The detailed configuration of the wave retardation plate 32 will be described later.

  The cooling jacket 34 has a flow path 34a through which the refrigerant can flow, and cools the slow wave plate 32 and the slot plate 30 by the flow of the refrigerant. The surface of the cooling jacket 34 has conductivity. A lower end of the outer conductor 28 a is electrically connected to the upper surface of the cooling jacket 34. Further, the lower end of the inner conductor 28 b is electrically connected to the slot plate 30 through a hole formed in the central portion of the cooling jacket 34 and the slow wave plate 32.

  The microwave from the coaxial waveguide 28 is propagated to the slow wave plate 32 and is introduced into the processing space S from the slot 30 a of the slot plate 30 through the dielectric window 20. The dielectric window 20 has a substantially disc shape and is made of, for example, quartz. The dielectric window 20 is provided between the processing space S and the antenna 18. In one embodiment, the dielectric window 20 is provided immediately below the antenna 18 in the axis X direction.

  In one embodiment, a conduit 36 passes through the inner hole of the inner conductor 28 b of the coaxial waveguide 28. A through hole 30 d through which the conduit 36 can penetrate is formed at the center of the slot plate 30. The conduit 36 extends along the axis X and is connected to a gas supply system 38, a gas supply system 39, and a gas supply system 40.

  The gas supply system 38 supplies a processing gas for processing the substrate W to be processed to the conduit 36. The processing gas supplied by the gas supply system 38 contains carbon. In one embodiment, this processing gas is an etching gas, for example, CF4 gas or CH2F2 gas. The gas supply system 38 may include a gas source 38a, a valve 38b, and a flow controller 38c. The gas source 38a is a processing gas source. The valve 38b switches supply and stop of supply of the processing gas from the gas source 38a. The flow rate controller 38c is a mass flow controller, for example, and adjusts the flow rate of the processing gas from the gas source 38a.

  The gas supply system 39 supplies oxygen gas (O 2 gas) to the conduit 36. The oxygen gas supplied from the gas supply system 39 constitutes a cleaning gas. The gas supply system 39 may include a gas source 39a, a valve 39b, and a flow rate controller 39c. The gas source 39a is a gas source of oxygen gas. The valve 39b switches between supply and stop of gas supply from the gas source 39a. The flow rate controller 39c is a mass flow controller, for example, and adjusts the flow rate of the gas from the gas source 39a.

  The gas supply system 40 supplies argon gas to the conduit 36. In one embodiment, in addition to the cleaning gas from the gas supply system 39, argon gas is supplied from the gas supply system 40. The gas supply system 40 may include a gas source 40a, a valve 40b, and a flow rate controller 40c. The gas source 40a is a gas source of argon gas. The valve 40b switches supply and stop of supply of argon gas from the gas source 40a. The flow rate controller 40c is, for example, a mass flow controller, and adjusts the flow rate of argon gas from the gas source 40a.

  In one embodiment, the plasma processing apparatus 10 may further include an injector 41. The injector 41 supplies the gas from the conduit 36 to the through hole 20 h formed in the dielectric window 20. The gas supplied to the through hole 20 h of the dielectric window 20 is supplied to the processing space S. In the following description, the gas supply path constituted by the conduit 36, the injector 41, and the through hole 20h may be referred to as a “central gas introduction unit”.

  In one embodiment, the plasma processing apparatus 10 may further include a gas supply unit 42. The gas supply unit 42 supplies gas from the periphery of the axis X to the processing space S between the stage 14 and the dielectric window 20. In the following description, the gas supply unit 42 may be referred to as “peripheral gas introduction unit”. The gas supply unit 42 includes a conduit 42a. The conduit 42 a extends annularly around the axis X between the dielectric window 20 and the stage 14. A plurality of gas supply holes 42b are formed in the conduit 42a. The plurality of gas supply holes 42b are arranged in an annular shape and open toward the axis X, and supply the gas supplied to the conduit 42a toward the axis X. The gas supply unit 42 is connected to a gas supply system 43, a gas supply system 44, and a gas supply system 45 through a conduit 46.

  The gas supply system 43 supplies the gas supply unit 42 with a processing gas for processing the substrate W to be processed. The processing gas supplied from the gas supply system 43 contains carbon, similar to the processing gas of the gas supply system 38. In one embodiment, this processing gas is an etching gas, for example, CF4 gas or CH2F2 gas. The gas supply system 43 may include a gas source 43a, a valve 43b, and a flow rate controller 43c. The gas source 43a is a gas source of the processing gas. The valve 43b switches supply and stop of supply of the processing gas from the gas source 43a. The flow rate controller 43c is a mass flow controller, for example, and adjusts the flow rate of the processing gas from the gas source 43a.

  The gas supply system 44 supplies oxygen gas (O 2 gas) to the gas supply unit 42. The gas supplied from the gas supply system 44 constitutes a cleaning gas. The gas supply system 44 may include a gas source 44a, a valve 44b, and a flow rate controller 44c. The gas source 44a is a gas source of oxygen gas. The valve 44b switches between supply and stop of gas supply from the gas source 44a. The flow rate controller 44c is a mass flow controller, for example, and adjusts the flow rate of the gas from the gas source 44a.

  The gas supply system 45 supplies argon gas to the gas supply unit 42. In one embodiment, in addition to the cleaning gas from the gas supply system 44, argon gas is supplied from the gas supply system 45. The gas supply system 45 may include a gas source 45a, a valve 45b, and a flow rate controller 45c. The gas source 45a is a gas source of argon gas. The valve 45b switches between supply and stop of supply of argon gas from the gas source 45a. The flow rate controller 45c is, for example, a mass flow controller, and adjusts the flow rate of argon gas from the gas source 45a.

  The stage 14 is provided so as to face the dielectric window 20 in the axis X direction. The stage 14 is provided so as to sandwich the processing space S between the dielectric window 20 and the stage 14. A substrate W to be processed is placed on the stage 14. In one embodiment, the stage 14 includes a table 14a, a focus ring 14b, and an electrostatic chuck 14c.

  The base 14a is supported by a cylindrical support portion 48. The cylindrical support portion 48 is made of an insulating material and extends vertically upward from the bottom portion 12b. A conductive cylindrical support 50 is provided on the outer periphery of the cylindrical support 48. The cylindrical support portion 50 extends vertically upward from the bottom portion 12 b of the processing container 12 along the outer periphery of the cylindrical support portion 48. An annular exhaust passage 51 is formed between the cylindrical support portion 50 and the side wall 12a.

  An annular baffle plate 52 provided with a plurality of through holes is attached to the upper portion of the exhaust passage 51. An exhaust device 56 is connected to the lower portion of the exhaust hole 12 h via an exhaust pipe 54. The exhaust device 56 has a vacuum pump such as a turbo molecular pump. The exhaust device 56 can depressurize the processing space S in the processing container 12 to a desired degree of vacuum.

  The base 14a also serves as a high-frequency electrode. A high frequency power source 58 for RF bias is electrically connected to the base 14 a via a power feed rod 62 and a matching unit 60. The high frequency power supply 58 outputs a predetermined frequency suitable for controlling the energy of ions drawn into the substrate W to be processed, for example, a high frequency power of 13.65 MHz at a predetermined power. The matching unit 60 accommodates a matching unit for matching between the impedance on the high-frequency power source 58 side and the impedance on the load side such as electrodes, plasma, and the processing container 12. This matching unit includes a blocking capacitor for generating a self-bias.

  An electrostatic chuck 14c is provided on the upper surface of the table 14a. The electrostatic chuck 14c holds the substrate W to be processed with an electrostatic attraction force. A focus ring 14b that surrounds the periphery of the substrate W to be processed is provided on the outer side in the radial direction of the electrostatic chuck 14c. The electrostatic chuck 14c includes an electrode 14d, an insulating film 14e, and an insulating film 14f. The electrode 14d is made of a conductive film, and is provided between the insulating film 14e and the insulating film 14f. A high-voltage DC power supply 64 is electrically connected to the electrode 14 d via a switch 66 and a covered wire 68. The electrostatic chuck 14c can attract and hold the substrate W to be processed by the Coulomb force generated by the DC voltage applied from the DC power source 64.

  An annular refrigerant chamber 14g extending in the circumferential direction is provided inside the table 14a. A refrigerant having a predetermined temperature, for example, cooling water, is circulated and supplied to the refrigerant chamber 14g from a chiller unit (not shown) via pipes 70 and 72. The upper surface temperature of the electrostatic chuck 14c is controlled by the temperature of the refrigerant. A heat transfer gas, for example, He gas is supplied between the upper surface of the electrostatic chuck 14c and the back surface of the substrate W to be processed via the gas supply pipe 74, and the substrate to be processed is determined by the upper surface temperature of the electrostatic chuck 14c. The temperature of W is controlled.

  In the plasma processing apparatus 10 configured as described above, gas is supplied along the axis X into the processing space S from the through hole 20h of the dielectric window 20 via the through hole of the conduit 36 and the injector 41. Further, gas is supplied from the gas supply unit 42 toward the axis X below the through hole 20h. Further, microwaves are introduced from the antenna 18 through the dielectric window 20 into the processing space S and / or the through hole 20 h. Thereby, plasma is generated in the processing space S and / or the through hole 20h. Thus, according to the plasma processing apparatus 10, plasma can be generated without applying a magnetic field.

  Next, a detailed configuration of the slow wave plate 32 will be described with reference to FIG. FIG. 3 is a perspective view showing a state in which the slow wave plate and the slot plate are combined in one embodiment. As shown in FIG. 3, the slow wave plate 32 is formed in a substantially gear shape whose plate surface is orthogonal to the axis X. The slow wave plate 32 is provided between the slot plate 30 and the plate side surface of the cooling jacket 34. The slow wave plate 32 includes a disk-shaped main body portion 32a and a plurality of extending portions 32b extending from the main body portion 32a. A substantially cylindrical hole for arranging the inner conductor 28b of the coaxial waveguide 28 is provided at the center of the main body 32a. A ring-shaped projecting portion 32 c projecting in the thickness direction of the slow wave plate 32 is provided at an inner diameter side end portion of the main body portion 32 a forming the periphery of the hole. The microwave that has propagated through the gap between the inner conductor 28b and the outer conductor 28a of the coaxial waveguide 28 is input to the main body 32a via the protrusion 32c, propagates through the main body 32a, and then has a plurality of extending portions. 32b.

  The plurality of extending portions 32 b extend radially in the radial direction of the slot plate 30 around the axis X so as to cover the plurality of slots 30 a of the slot plate 30, respectively. When a microwave is input from the main body portion 32 a, the plurality of extending portions 32 b supply the input microwave to each of the plurality of slots 30 a of the slot plate 30. The microwaves supplied from the plurality of extending portions 32 b to each of the plurality of slots 30 a of the slot plate 30 are radiated from the plurality of slots 30 a to the processing space S through the dielectric window 20. Then, the microwaves reflected in the processing space S (hereinafter referred to as “microwave reflected waves”) return from the plurality of slots 30 a of the slot plate 30 to the plurality of extending portions 32 b and extend along the radial direction of the slot plate 30. And propagates through the plurality of extending portions 32b.

  Moreover, it is preferable that the width W1 of each of the plurality of extending portions 32b is set in a range of 1/2 to 1 times the wavelength of the microwave propagating through the slow wave plate 32. Moreover, it is preferable that each thickness T1 of the some extension part 32b is shorter than each width W1 of the some extension part 32b. For example, the thickness T1 of each of the plurality of extending portions 23 is preferably set to a length less than ½ times the wavelength of the microwave propagating through the slow wave plate 32. Thus, by setting the shape of each of the plurality of extending portions 32b, the TE10 mode in which the distribution of the microwave propagating through each of the plurality of extending portions 32b or the distribution of the reflected waves of the microwave is the fundamental mode. Fixed to.

  The shielding member 35 is disposed in a space 32b-1 sandwiched between the extending portions 32b adjacent to each other among the plurality of extending portions 32b. The shielding member 35 is formed in a shape corresponding to the shape of the space 32b-1 by a conductor, for example, and shields the microwave. By arranging the shielding member 35 in the space 32b-1, the reflected wave of the microwave leaking from the extending part 32b to the space 32b-1 propagates to the other extending part 32b via the space 32b-1. The interference between the reflected waves of the microwaves can be avoided more reliably.

  The shielding member 35 is disposed in the space 32b-1 by being attached to the slot plate 30. Thereby, the reflected wave of the microwave leaking into the area near the slot plate 30 in the space 32b-1 is efficiently blocked by the shielding member 35.

  FIG. 4 is a diagram illustrating a simulation result of the electric field intensity distribution in the slow wave plate according to the embodiment. In FIG. 4, shades of color indicate the strength of the electric field strength. As shown in FIG. 4, the slow wave plate 32 has a plurality of extending portions 32b covering the plurality of slots 30a, so that the reflected wave of the microwave is in the radial direction of the slot plate 30 (the direction of the arrow in FIG. 4). Along the plurality of extending portions 32b. Thereby, the situation where the reflected wave of the microwave propagates through the slow wave plate 32 along the circumferential direction of the slot plate 30 is avoided, and the interference between the reflected waves of the microwave is avoided. In this way, by avoiding interference between the reflected waves of the microwaves, as shown in FIG. 4, the circumferential direction of the slot plate 30 generated in the slow wave plate 32 due to the reflected waves of the microwaves. It is possible to suppress the deviation of the electric field strength along the line.

  As described above, in the plasma processing apparatus 10 according to the embodiment, the slow wave plate 32 includes the plurality of extending portions 32b extending in the radial direction of the slot plate 30 so as to cover the plurality of slots 30a, so that the plurality of extending portions are provided. The reflected wave of the microwave can be propagated along the radial direction of the slot plate 30 within 32b. As a result, according to the plasma processing apparatus 10 of one embodiment, it is possible to suppress the deviation of the electric field intensity along the circumferential direction of the slot plate 30 that occurs in the slow wave plate 32.

  In the above-described embodiment, the example in which the shielding member 35 is disposed in the space 32b-1 by being attached to the slot plate 30 has been described, but the disclosed technology is not limited thereto. For example, the shielding member 35 may be disposed in the space 32b-1 by being attached to the cooling jacket 34. As a result, the interference between the reflected waves of microwaves can be further suppressed, and the heat of the space 32b-1 can be efficiently released from the cooling jacket 34.

DESCRIPTION OF SYMBOLS 10 Plasma processing apparatus 12 Processing container 14 Stage 16 Microwave generator 18 Antenna 20 Dielectric window 30 Slot plate 30a Slot 32 Slow wave plate 32b Extension part 34 Cooling jacket 35 Shielding member

Claims (7)

A processing vessel defining a processing space;
A dielectric having a facing surface facing the processing space;
A slot plate provided on a surface opposite to the facing surface of the dielectric, and a plurality of slots for radiating microwaves for generating plasma to the processing space via the dielectric , A slot plate disposed along a circumferential direction around a line in a direction in which the center of the processing container extends ;
A slow wave plate provided on the slot plate, extending radially in the radial direction of the slot plate around the line so as to cover the plurality of slots, and applying the microwave to each of the plurality of slots A plasma processing apparatus comprising: a retardation plate having a plurality of extending portions to be supplied.   2. The plasma processing apparatus according to claim 1, wherein a shielding member that shields the microwave is disposed in a space sandwiched between extension portions adjacent to each other among the plurality of extension portions. A cooling jacket provided on the slow wave plate;
The plasma processing apparatus according to claim 2, wherein the shielding member is disposed in the space by being attached to the cooling jacket.   The plasma processing apparatus according to claim 2, wherein the shielding member is disposed in the space by being attached to the slot plate.   5. The width of each of the plurality of extending portions is set in a range of ½ to 1 times the wavelength of the microwave propagating through the slow wave plate. The plasma processing apparatus according to any one of the above.   The plasma processing apparatus according to claim 5, wherein a thickness of each of the plurality of extending portions is shorter than a width of each of the plurality of extending portions.   7. The plasma processing according to claim 6, wherein the thickness of each of the plurality of extending portions is set to a length less than ½ times the wavelength of the microwave propagating through the slow wave plate. apparatus.