Plasma processing equipment

Abstract

The present invention provides a plasma processing device, comprising: a coaxial tube extending in a vertical direction to form a portion of a high-frequency waveguide; a substrate support portion for supporting a substrate; an electrode having a gas flow path connected to a gas ejection port opening into a space above the substrate support portion, the electrode being disposed above the substrate support portion and centrally connected to an inner conductor of the coaxial tube; an expanded diameter portion forming a portion of the high-frequency waveguide together with the electrode and connected to an outer conductor of the coaxial tube; and a dielectric tube composed of a dielectric, connected to the electrode so as to penetrate a space between the electrode and the expanded diameter portion and for supplying gas to the electrode, wherein a plurality of the dielectric tubes are disposed in a dispersed manner.

Description

Technical Field

[0001] The present disclosure relates to a plasma processing apparatus. Background Art

[0002] Patent document 1 discloses a plasma processing device, which includes a shower plate having an upper electrode and an inlet portion provided on the lower side of the outer peripheral portion of the shower plate. The plasma processing device includes a waveguide portion for supplying high-frequency waves (VHF waves) to the inlet portion. The waveguide portion provides a cylindrical waveguide extending in the vertical direction. The lower end of the waveguide is connected to the inlet portion. The waveguide is provided by the space between the outer peripheral surface of the upper electrode and the inner surface of the cylindrical member. In addition, the upper wall portion that constitutes the waveguide together with the upper surface of the upper electrode is located at the upper end of the cylindrical member. In addition, a gas passage that connects the gas passage of the upper wall portion with the gas passage in the upper electrode is provided in the plasma processing device. The gas passage is composed of two concentric insulating cylinders and is composed of SiO2, Al2O3, etc.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-92024 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] The present disclosure relates to a technology for suppressing power loss caused by a dielectric tube for supplying gas to an electrode when the dielectric tube is provided through a high-frequency waveguide in a plasma processing apparatus that performs plasma processing using plasma generated by high-frequency waves.

[0008] Solutions for solving problems

[0009] One embodiment of the present disclosure is a plasma processing apparatus comprising: a coaxial tube extending in a vertical direction to form a portion of a high-frequency waveguide; a substrate support portion for supporting a substrate; an electrode having a gas flow path connected to a gas ejection port opening into a space above the substrate support portion, the electrode being disposed above the substrate support portion and centrally connected to an inner conductor of the coaxial tube; an expanded diameter portion forming a portion of the high-frequency waveguide together with the electrode and connected to an outer conductor of the coaxial tube; and a dielectric tube composed of a dielectric, connected to the electrode so as to penetrate a space between the electrode and the expanded diameter portion and for supplying gas to the electrode, wherein a plurality of the dielectric tubes are provided in a dispersed manner.

[0010] Effects of the Invention

[0011] According to the present disclosure, in a plasma processing apparatus that performs plasma processing using plasma generated by high-frequency waves, when a dielectric tube for supplying gas to an electrode is provided through a high-frequency waveguide, power loss caused by the dielectric tube can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a longitudinal sectional view schematically showing the outline of the structure of a film forming apparatus as a plasma processing apparatus according to this embodiment.

[0013] Figure 2 It is an enlarged view showing the cover and the shower head electrode.

[0014] Figure 3 2 is a cross-sectional view of a processing container showing the arrangement of dielectric tubes.

[0015] Figure 4 It is a cross-sectional view partially showing a film-forming apparatus for explaining simulation conditions.

[0016] Figure 5 This is a diagram showing simulation results regarding the relationship between the distance between the gas supply pipe and the protrusion and the absorption efficiency, which is the efficiency of absorbing the power of the plasma generated in the processing container.

[0017] Figure 6 1 is a diagram showing simulation results regarding the relationship between the distance between the protrusion and the resonator and the absorption efficiency, which is the efficiency of absorbing the power of the plasma generated in the processing container.

[0018] Figure 7 It is a diagram showing another example of the protrusion. DETAILED DESCRIPTION

[0019] As a process in the manufacturing process of semiconductors and the like, there is plasma processing in which plasma generated by high-frequency waves is used to form a film or etch a substrate such as a semiconductor wafer (hereinafter referred to as a “wafer”).

[0020] As a plasma processing device for performing plasma processing as described above, there is a plasma processing device comprising a coaxial tube, a substrate support portion, a shower head electrode, an expanded diameter portion, and a dielectric tube. The coaxial tube is arranged to extend in the vertical direction to form a part of a high-frequency waveguide. The substrate support portion is used to support the substrate. The shower head electrode is arranged above the substrate support portion and has a gas flow path connected to a gas ejection port opening to the space above the substrate support portion. In addition, the shower head electrode is centrally connected to the inner conductor of the coaxial tube. The expanded diameter portion forms a part of the high-frequency waveguide together with the shower head electrode and is connected to the coaxial tube. The dielectric tube is composed of a dielectric such as Al2O3 (aluminum oxide). The dielectric tube is connected to the shower head electrode in a manner that penetrates the space between the shower head electrode and the expanded diameter portion in the vertical direction. Moreover, the dielectric tube supplies gas from a gas supply source outside the expanded diameter portion to the shower head electrode via the expanded diameter portion.

[0021] The plasma processing apparatus disclosed in Patent Document 1 features a gas passageway composed of SiO₂ and Al₂O₃, etc., connecting the gas passageway in the upper wall portion, which forms a waveguide along the upper surface of the upper electrode, with the gas passageway within the upper electrode. This gas passageway is constructed from two concentric cylindrical bodies. Specifically, in the plasma processing apparatus disclosed in Patent Document 1, the gas inlet and gas supply port of the dielectric tube are formed into a circular ring centered on the center of the upper electrode when viewed from above. When using a dielectric tube of the shape disclosed in Patent Document 1, the diameter of each cylindrical body constituting the dielectric tube, when viewed from above, must be increased to ensure uniform gas supply to the space above the substrate support. However, high-frequency waves are absorbed by the dielectric tube, so using a large dielectric tube as described above leaves room for improvement in terms of power efficiency.

[0022] Therefore, the technology disclosed herein reduces power loss caused by a dielectric tube when a dielectric tube for supplying gas to an electrode is provided through a high-frequency waveguide in a plasma processing apparatus that performs plasma processing using plasma generated by high-frequency waves.

[0023] Next, refer to the attached Figure 1 In this specification, elements having substantially the same functional structure are denoted by the same reference numerals to omit redundant description.

[0024] <Film Forming Apparatus 1>

[0025] Figure 1 It is a longitudinal sectional view schematically showing the outline of the structure of a film forming apparatus 1 as a plasma processing apparatus according to the present embodiment. Figure 2This is an enlarged view showing a cover body and shower head electrodes to be described later.

[0026] Figure 1 The film forming apparatus 1 performs a film forming process on a wafer W serving as a substrate, as a plasma process using plasma generated by high-frequency waves. In this specification, high-frequency waves refer to high-frequency electromagnetic waves, and high frequency refers to frequencies lower than microwaves, including 30 MHz to 300 MHz, namely VHF (very high frequency).

[0027] The film forming apparatus 1 is used to form a SiN film on a wafer W, for example.

[0028] The film forming apparatus 1 includes a processing container 10 having a plasma processing space S formed therein. The processing container 10 is disposed such that its central axis AX extends in a vertical direction. The plasma processing space S is formed in the processing container 10 between a mounting table 20 (described later) and a showerhead electrode 30 provided within the processing container 10.

[0029] The processing container 10 includes a container body 11 and a cover 12. The container body 11 and the cover 12 are formed of aluminum or the like and are electrically connected to a ground potential.

[0030] The container body 11 is formed into a hollow shape having an opening 11a. Specifically, it is formed into a bottomed cylindrical shape with an opening 11a at the top. The central axis of the container body 11 and the sidewalls of the container body 11 coincides with the central axis AX of the processing container 10. Although not shown, an exhaust device is connected to the bottom of the container body 11 via an APC valve (not shown) or the like to reduce the pressure inside the processing container 10, specifically, to reduce the pressure in the plasma processing space S.

[0031] The lid 12 is formed in a disk shape having a through hole 12a at the center and is attached to the upper side of the container body 11 so as to cover the peripheral edge of the opening 11a of the container body 11.

[0032] In addition, if Figure 2 As shown, the cover 12 has gas flow passages 12b at positions corresponding to gas introduction passages 33, which will be described later. The gas flow passages 12b are connected to process gas supply sources 200 provided outside the processing container 10, and are used to supply process gas from the process gas supply sources 200 to the showerhead electrode 30, which will be described later, within the processing container 10.

[0033] The central axis of the cover 12 and the through hole 12 a coincides with the central axis AX of the processing container 10 .

[0034] like Figure 1As shown, a mounting table 20 serving as a substrate support portion is provided below the plasma processing space S in the processing container 10 . The mounting table 20 supports a wafer W horizontally mounted on an upper surface of the mounting table 20 .

[0035] The stage 20 is supported, for example, by a support member 21 erected in the center of the bottom of the container body 11. Although not shown in the figure, a heater for heating the wafer W is provided on the stage 20. In addition, a cooling mechanism having a refrigerant flow path for circulating a refrigerant for cooling may be provided instead of a heating mechanism such as a heater, or both a heating mechanism and a cooling mechanism may be provided. In addition, an elevator (not shown) is provided in such a manner that it can move up and down relative to the stage 20. The elevator is used to transfer the wafer W between a conveying device (not shown) for inserting the wafer W from the outside of the processing container 10 into the processing container 10 and the stage 20.

[0036] A shower head electrode 30 is provided above the plasma processing space S of the mounting table 20 in the processing container 10 at a position facing the mounting table 20 .

[0037] The shower head electrode 30 is formed of, for example, a conductive material, specifically, a metal material such as aluminum, and has a disk shape.

[0038] A plurality of gas ejection ports 31 opening into the plasma processing space S are provided at the lower portion of the shower head electrode 30, i.e., at the plasma processing space S side. In addition, a gas diffusion chamber 32 serving as a gas flow path connected to the gas ejection ports 31 is provided inside the shower head electrode 30. The gas diffusion chamber 32 is formed, for example, in a substantially disk shape. Figure 2 As shown, multiple gas introduction paths 33 are provided on the circumference of the upper portion of the showerhead electrode 30. One end of each gas introduction path 33 is connected to the gas diffusion chamber 32, and the other end is connected to one end of a different dielectric tube 40. The other end of each dielectric tube 40 is connected to the gas flow path 12b of the cover 12.

[0039] Process gas from a process gas supply source 200 located outside the processing container 10 is supplied to the shower head electrode 30 via the gas flow path 12 b of the cover 12 and the dielectric tube 40. Specifically, the process gas is supplied to the gas diffusion chamber 32 via the gas flow path 12 b, the dielectric tube 40, and the gas introduction path 33, and is ejected into the plasma processing space S via the gas ejection port 31. The process gas supplied from the process gas supply source 200 includes, for example, excitation gases such as argon, silane gas for forming a SiN film, and nitrogen gas.

[0040] The dielectric tube 40 will be described in detail later.

[0041] like Figure 1As shown, the shower head electrode 30 is supported by the processing container 10 via a dielectric window 50 made of a dielectric such as alumina.

[0042] The upper and lower spaces within the processing container 10 are separated by the showerhead electrode 30 and the dielectric window 50. Therefore, when the processing container 10 is depressurized by the exhaust device, the space above the dielectric window 50 is maintained at atmospheric pressure.

[0043] The dielectric window 50 is formed in a circular shape in plan view and is provided to cover the outer peripheral surface of the shower head electrode 30. The dielectric window 50 introduces high-frequency waves propagating through the waveguide 100 described later from the outer periphery of the shower head electrode 30 into the plasma processing space S.

[0044] The central axes of the shower head electrode 30 and the dielectric window 50 coincide with the central axis AX of the processing container 10 .

[0045] A gas introduction path 34 is provided at the center of the upper portion of the shower head electrode 30 . One end of the gas introduction path 34 is connected to the gas diffusion chamber 32 , and the other end opens to the gas supply path inside the gas supply pipe 60 .

[0046] The gas supply pipe 60 is formed cylindrically from a metal material such as aluminum, and its lower end is connected to the center of the upper surface of the shower head electrode 30. The gas supply pipe 60 extends vertically and passes through the through hole 12a of the cover 12.

[0047] The central axis of the gas supply pipe 60 coincides with the central axis AX of the processing container 10 .

[0048] The cleaning gas supplied from the gas supply source 210 and converted to plasma by the remote plasma source 220 is introduced into the gas supply pipe 60. The plasma-converted cleaning gas introduced into the gas supply pipe 60 is supplied to the plasma processing space S via the gas introduction path 34, the gas diffusion chamber 32, and the gas ejection port 31.

[0049] In order to prevent active species contained in the plasma-generated cleaning gas from colliding with the gas supply pipe 60 and being deactivated, the inner diameter of the gas supply pipe 60 is set large, for example, to 30 mm or more.

[0050] The gas supply pipe 60 also includes a flange portion 61. The flange portion 61 is provided, for example, at the center of the gas supply pipe 60 in the vertical direction. The flange portion 61 is formed into a circular ring shape when viewed from above, and is provided to protrude radially outward from the outer circumference of the gas supply pipe 60. The diameter of the portion of the gas supply pipe 60 other than the flange portion 61 is, for example, 40 mm.

[0051] Furthermore, a covering conductor 70 is provided above the processing container 10 so as to surround the upper portion of the gas supply pipe 60 protruding from the through-hole 12a of the lid 12. The covering conductor 70 is formed into a cylindrical shape from a metal material such as aluminum, and its lower end is connected to the upper surface of the lid 12. The inner diameter of the covering conductor 70 is, for example, substantially the same as the diameter of the through-hole 12a of the lid 12. The central axis of the covering conductor 70 coincides with the central axis AX of the processing container 10 and the central axis of the gas supply pipe 60.

[0052] Furthermore, the covering conductor 70 has a cover 71 having a circular ring shape in a plan view at its upper end. The cover 71 closes the space between the inner peripheral surface of the covering conductor 70 and the gas supply pipe 60 .

[0053] A hole 72 is provided at the height of the flange portion 61 of the gas supply pipe 60, covering the side portion of the conductor 70. A power supply rod 80 is provided horizontally extending through the hole 72. One end of the power supply rod 80 is connected to the side end of the flange portion 61 of the gas supply pipe 60 (specifically, the end facing the hole 72). The other end of the power supply rod 80 is connected to a power supply 91 via a matching device 90. The matching device 90 matches the internal impedance of the power supply 91 with the load impedance of the power supply 91. The power supply 91 outputs high-frequency (e.g., VHF) power.

[0054] By supplying high-frequency power from the power source 91 to the power supply rod 80 , high-frequency waves are supplied to the space between the inner peripheral surface of the covering conductor 70 and the gas supply pipe 60 .

[0055] Furthermore, the upper portion of the covering conductor 70 and the upper portion of the gas supply pipe 60 constitute the resonator K. Specifically, the portion of the covering conductor 70 above the flange 61 and the portion of the gas supply pipe 60 above the flange 61 constitute the resonator K. The high-frequency waves introduced into the resonator K are generated by supplying high-frequency power to the power supply rod 80 connected to the side end of the flange 61. In other words, the high-frequency waves are introduced into the resonator K from the side (horizontally).

[0056] The entire internal space of the resonator K (specifically, the region between the lower surface of the flange 61 and the lower surface of the cover 71 in the space between the gas supply pipe 60 and the covering conductor 70 ) is filled with polytetrafluoroethylene (PTFE).

[0057] To ensure that only desired high-frequency waves exist within resonator K, the outer radius r of flange 61, the thickness t of flange 61, and the distance L between the lower surface of flange 61 and the lower surface of cover 71 covering conductor 70 satisfy the following equation, for example. Furthermore, λg is the effective wavelength of the electromagnetic wave.

[0058] λg / (4×π)-λg / (30×π)≤r≤λg / (4×π)…(1)

[0059] 18(mm)≤t≤40(mm)…(2)

[0060] λg / 6≤L≤λg / 5…(3)

[0061] When the frequency of the high-frequency wave is 220 MHz and the entire internal space of the resonator K is filled with PTFE, equations (1) and (3) are expressed by the following equations (1a) and (3a).

[0062] 67(mm)≤r≤73(mm)…(1a)

[0063] 158(mm)≤L≤183(mm)…(3a)

[0064] A covering conductor 81 is provided, extending from the covering conductor 70, to cover the outer periphery of the power supply rod 80. Like the covering conductor 70, the covering conductor 81 is formed cylindrically from a metal material such as aluminum. The central axis of the covering conductor 81 coincides with the central axis of the power supply rod 80.

[0065] The film forming apparatus 1 further includes a high-frequency waveguide (hereinafter abbreviated as "waveguide") 100. The waveguide 100 transmits high-frequency waves generated by supplying high-frequency power from a power supply 91 to the power supply rod 80 to the plasma processing space S. More specifically, the waveguide 100 transmits the high-frequency waves resonating in the resonator K to the plasma processing space S. The waveguide 100 includes a first waveguide 101 to a third waveguide 103.

[0066] The first waveguide 101 is formed by a coaxial tube extending in the vertical direction. Specifically, the inner conductor of the coaxial tube is the portion of the gas supply pipe 60 below the flange 61. Furthermore, the outer conductor of the coaxial tube is the portion of the cover conductor 70 below the flange 61 and the wall of the lid 12 forming the through-hole 12a. The first waveguide 101 transmits high-frequency waves downward along the central axis AX of the processing chamber 10, which coincides with the axial direction of the coaxial tube.

[0067] The covering conductor 70 constituting the first waveguide 101 is provided with a protrusion 73 having an annular shape in plan view and protruding inward from the inner circumference of the covering conductor 70. The protrusion 73 is formed of a metal material such as aluminum, similar to the covering conductor 70. The protrusion 73 is provided, for example, near the cover 12.

[0068] The second waveguide 102 is continuous with the first waveguide 101 and is divided by the lower surface of the cover 12, which serves as an expanded diameter portion, and the upper surface of the showerhead electrode 30. The second waveguide 102 transmits high-frequency waves radially outward in a plan view. The dielectric tube 40 is located within the second waveguide 102.

[0069] The second waveguide 102 may be partially filled with a dielectric material other than air (quartz, etc.). More specifically, the portion of the second waveguide 102 outside the dielectric tube 40 may be filled with quartz, etc. Alternatively, the entire second waveguide 102, excluding the portion where the dielectric tube 40 is disposed, may be filled with quartz, etc.

[0070] The third waveguide 103 is continuous with the second waveguide 102 and is divided by the outer circumferential surface of the showerhead electrode 30 and the inner circumferential surface of the sidewall of the container body 11. Furthermore, the third waveguide 103 is provided with a dielectric window 50. The third waveguide 103 transmits high-frequency waves downward along the outer circumferential surface of the showerhead electrode 30, and introduces the high-frequency waves into the plasma processing space S through the dielectric window 50.

[0071] The first to third waveguides 101 to 103 are each formed in a ring shape in plan view. In addition, the third waveguide 103 at the end portion of the waveguide 100 located on the plasma processing space S side is formed to surround the outer periphery of the shower head electrode 30 .

[0072] In the film-forming apparatus 1, high-frequency waves from the resonator K propagate through the first waveguide 101, the second waveguide 102, and the third waveguide 103, and are introduced into the plasma processing space S via the dielectric window 50. The introduced high-frequency waves generate plasma in the plasma processing space S. This plasma is used to process the wafer W. To attract ions and the like in the plasma to the wafer W, the mounting table 20 may be electrically connected to a power supply for RF bias via a matching box, for example. The power supply for RF bias outputs high-frequency power in the range of 400 kHz to 20 MHz, for example.

[0073] The film forming apparatus 1 also includes a control unit U. The control unit U is comprised of, for example, a computer equipped with a CPU, memory, and the like, and includes a program storage unit (not shown). The program storage unit stores programs for controlling the power supply 91 and other functions for performing various processes in the film forming apparatus 1. These programs can be recorded on a computer-readable storage medium and installed from the storage medium into the control unit U.

[0074] <Dielectric Tube 40>

[0075] Next, refer to Figure 1 and Figure 2 ,use Figure 3 The dielectric tube 40 will be described. Figure 3A cross-sectional view of the processing container 10 showing how the dielectric tube 40 is arranged.

[0076] The dielectric tube 40 is formed into a cylindrical shape by dielectric materials such as alumina. Figure 1 and Figure 2 As shown, the dielectric tube 40 is connected to the showerhead electrode 30, extending through the space between the showerhead electrode 30 and the cover 12. Specifically, the dielectric tube 40 is connected to the showerhead electrode 30, extending in a direction perpendicular to the propagation direction of the high-frequency wave through the second waveguide 102, which is defined by the upper surface of the showerhead electrode 30 and the lower surface of the cover 12. More specifically, the dielectric tube 40 extends vertically through the second waveguide 102, which is defined by the upper surface of the showerhead electrode 30 and the lower surface of the cover 12 and extends horizontally. One end of the dielectric tube 40 is connected to the upper surface of the showerhead electrode 30, and the other end is connected to the lower surface of the cover 12. The dielectric tube 40 establishes fluid communication between the gas introduction path 33 of the showerhead electrode 30 and the gas flow path 12b of the cover 12 corresponding to the gas introduction path 33.

[0077] In the film forming apparatus 1, a plurality of gas introduction paths 33 of the shower head electrode 30 and gas flow paths 12b of the cover 12 are provided in a dispersed manner, and the dielectric tube 40 for fluidly connecting them is also provided. Figure 3 As shown, a plurality of dielectric tubes 40 (four in the example shown) are arranged in a dispersed manner. Specifically, the dielectric tubes 40 are arranged at equal intervals on the same circumference centered on the central axis AX of the processing chamber 10 (i.e., the central axis of the coaxial tube forming the first waveguide 101) when viewed from above. The number of dielectric tubes 40 is, for example, four to eight. Furthermore, the inner diameter of the dielectric tubes 40 is, for example, 0.6 mm to 10 mm, and the outer diameter is, for example, 5 mm to 20 mm.

[0078] When multiple dielectric tubes 40 are arranged in a distributed manner as described above (specifically, when the dielectric tubes 40 are arranged at equal intervals on the same circumference), the process gas can be uniformly supplied to the plasma processing space S via the showerhead electrode 30. Even when using the dielectric tubes disclosed in Patent Document 1, the process gas can be uniformly supplied to the plasma processing space S by increasing the size of the dielectric tubes. However, distributing multiple dielectric tubes 40 in a distributed manner as in this embodiment reduces the volume occupied by the dielectric tubes within the high-frequency waveguide. Therefore, according to this embodiment, power loss caused by the dielectric tubes 40 can be suppressed.

[0079] Furthermore, the dielectric tube 40 is smaller in volume than the components (specifically, the cylindrical body) constituting the dielectric tube disclosed in Patent Document 1. Therefore, the temperature is less likely to become uneven when the temperature rises due to absorption of high-frequency waves, thereby reducing the risk of damage due to thermal shock.

[0080] As in this embodiment, distributing multiple dielectric tubes 40 in a dispersed manner reduces the area of ​​the inner circumferential surface of the dielectric tube that forms the gas flow path, compared to using the dielectric tube (a large cylindrical body) disclosed in Patent Document 1. Specifically, this reduces the contact area between the gas flowing through the dielectric tube and the inner circumferential surface of the dielectric tube. Furthermore, when supplying the same amount of process gas to the showerhead electrode 30, distributing multiple dielectric tubes 40 in a dispersed manner reduces the time the process gas remains within the dielectric tube compared to using the dielectric tube disclosed in Patent Document 1. Consequently, this embodiment can suppress unnecessary thermal decomposition of the process gas caused by the dielectric tube heating up due to absorption of high-frequency waves.

[0081] As described above, according to this embodiment, the plurality of cylindrical dielectric tubes 40 are arranged in a dispersed manner. This can suppress power loss caused by the dielectric tubes 40 and reduce the risk of damage to the dielectric tubes 40 due to thermal shock. Furthermore, according to this embodiment, the plurality of cylindrical dielectric tubes 40 are arranged in a dispersed manner, thereby preventing unnecessary thermal decomposition of the process gas when passing through the dielectric tubes 40.

[0082] <Effects of the protrusion 73>

[0083] Furthermore, in this embodiment, as described above, the covering conductor 70 constituting the first waveguide 101 is provided with a protrusion 73 that protrudes inward from the inner circumference of the covering conductor 70. This protrusion 73 promotes the formation of an annular equipotential surface centered on the central axis (specifically, central axis AX) of the coaxial tube within the first waveguide 101, that is, within the coaxial tube formed by the covering conductor 70 and the like. Therefore, even if the high-frequency wave introduced into the first waveguide 101 is uneven in the circumferential direction centered on the central axis AX, the high-frequency wave transmitted from the first waveguide 101 to the second waveguide 102 can be made uniform in the circumferential direction. As a result, the high-frequency wave introduced into the plasma processing space S and the electric field formed in the plasma processing space S by the high-frequency wave are also uniform in the circumferential direction, thereby enabling more uniform in-plane plasma processing of the wafer W.

[0084] The closer the position of the protrusion 73 is to the second waveguide 102 , the more uniform the high-frequency waves introduced from the first waveguide 101 to the second waveguide 102 can be in the circumferential direction.

[0085] Furthermore, the present inventors have confirmed through simulations that the provision of protrusion 73 makes the distribution of the electric field formed in the plasma processing space S axially symmetric, compared to a case where protrusion 73 is not provided. Furthermore, the present inventors have confirmed through simulations that the provision of protrusion 73 improves the reflection coefficient Γ of the electric power, compared to a case where protrusion 73 is not provided.

[0086] <Simulation Related to Protrusion 73>

[0087] Next, regarding the conditions of the protrusion 73 , the results of simulations performed by the present inventors will be described. Figure 4 It is a cross-sectional view partially showing the film forming apparatus 1 for explaining simulation conditions. Figure 5 It is a diagram showing simulation results related to the relationship between the distance d and the absorption efficiency, where the distance d is the distance between the gas supply pipe 60 and the protrusion 73 (specifically, the distance between the outer peripheral surface of the gas supply pipe 60 and the inner peripheral surface of the protrusion 73), and the absorption efficiency is the absorption efficiency of the electricity of the plasma generated in the processing container 10. Figure 6 It is a diagram showing simulation results related to the relationship between the distance Δ and the absorption efficiency, where the distance Δ is the distance between the protrusion 73 and the resonator K (specifically, the distance between the upper surface of the protrusion 73 and the lower surface of the flange 61), and the absorption efficiency is the absorption efficiency of the electric power to the above-mentioned plasma.

[0088] The basic conditions for the simulation are as follows.

[0089] Diameter of wafer W: 300mm

[0090] Diameter of shower head electrode 30: 390mm

[0091] Pressure of plasma processing space S: 100 Torr

[0092] Inner diameter of container body 11: 430 mm

[0093] Outer diameter of dielectric tube 40: 266 mm

[0094] Inner diameter of dielectric tube 40: 234 mm

[0095] Number of dielectric tubes 40: 4

[0096] Intervals between dielectric tubes 40: Equal intervals

[0097] Material of dielectric tube 40: Alumina

[0098] Distance from central axis AX to center of dielectric tube 40: 125 mm

[0099] Diameter of the gas supply pipe 60 other than the flange 61: 50 mm

[0100] Inner diameter of covering conductor 70: 90 mm

[0101] Distance between the lower surface of the protrusion 73 and the upper surface of the cover 12: 2 mm

[0102] Frequency of power supplied to power supply rod 80: 220 MHz

[0103] In all simulations, it was assumed that the entire second waveguide 102 except for the portion where the dielectric tube 40 was provided was filled with quartz.

[0104] In addition, Figure 6 In the simulations for which the results are shown in , the following conditions were employed.

[0105] The distance Δ between the protrusion 73 and the resonator K (see Figure 4 ): 70mm

[0106] And, in Figure 5 In the simulations for which the results are shown in , the following conditions were employed.

[0107] The distance d between the gas supply pipe 60 and the protrusion 73 (see Figure 4 ): 15mm

[0108] When the power supply is 220MHz, Figure 5 As shown, when the distance d (mm) between the gas supply pipe 60 and the protrusion 73 satisfies the following formula (4), the efficiency of absorbing the power of the plasma generated in the processing container 10 becomes 60% or more.

[0109] 2≤d≤24…(4)

[0110] Furthermore, if the distance d is less than 2 mm, high-frequency waves will have difficulty passing between the gas supply pipe 60 and the protrusion 73, increasing the risk of discharge. From this perspective, when supplying 220 MHz power, the distance d between the gas supply pipe 60 and the protrusion 73 may be greater than 2 mm.

[0111] And, in the case of supplying 220MHz power, as Figure 6 As shown, when the distance Δ (mm) between the protrusion 73 and the resonator K satisfies the following formula (5), the efficiency of absorbing the power of the plasma generated in the processing container 10 becomes 60% or more.

[0112] 4≤Δ≤85…(5)

[0113] When the distance Δ is less than 4 mm, the resonance in the resonator K is inhibited. From this viewpoint, when supplying 220 MHz power, the distance Δ between the protrusion 73 and the resonator K may be 4 mm or more.

[0114] When the above equations (4) and (5) are converted into general equations that are independent of the frequency f of the power supplied to the power rod 80, that is, independent of the frequency f of the high-frequency wave, the following equations (4a) and (5a) are obtained.

[0115] 2*(220×10 6 ) / f≤d≤24*(220×10 6 ) / f…(4a)

[0116] 4*(220×10 6 ) / f≤Δ≤85*(220×10 6 ) / f…(5a)

[0117] <Modification>

[0118] In the above example, the protrusion 73 is provided so as to protrude inward from the inner peripheral surface of the covering conductor 70 , but the example of the protrusion 73 is not limited thereto. Figure 7 : is a diagram showing another example of a protrusion. Figure 7 As shown, the diameter of the through hole 12 a of the cover 12 may be made smaller than the inner diameter of the covering conductor 70 , and a portion 12 c of the cover 12 located inside the inner peripheral surface of the covering conductor 70 may be formed as a protrusion.

[0119] While the above description uses a film forming apparatus as an example, the technology disclosed herein can also be applied to plasma processing apparatuses that perform processes other than film forming, such as etching or doping.

[0120] The embodiments disclosed herein are to be considered in all respects as illustrative and non-restrictive, and the above embodiments may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the claims.

[0121] Description of Reference Numerals

[0122] 1: Film-forming device; 11: Container body; 12: Cover; 20: Loading table; 30: Shower head electrode; 31: Gas outlet; 32: Gas diffusion chamber; 40: Dielectric tube; 60: Gas supply tube; 70: Covering conductor; 100: High-frequency waveguide; 101: First waveguide; 102: Second waveguide; S: Plasma processing space; W: Wafer.

Claims

1. A plasma processing apparatus comprising: a coaxial tube, which is arranged to extend in an up-down direction and form a part of the high-frequency waveguide; a substrate supporting portion for supporting a substrate; an electrode having a gas flow path connected to a gas ejection port opening into a space above the substrate support portion, the electrode being provided above the substrate support portion and having an inner conductor of the coaxial tube connected at its center; an expanded diameter portion, which together with the electrode forms a part of the high-frequency waveguide and is connected to the outer conductor of the coaxial tube, and the expanded diameter portion is provided above the electrode; as well as a dielectric tube composed of a dielectric, connected to the electrode so as to penetrate a space defined by the upper surface of the electrode and the lower surface of the expanded diameter portion, and configured to supply gas to the electrode; Wherein, a plurality of the dielectric tubes are arranged in a dispersed manner.

2. The plasma processing apparatus according to claim 1, wherein The dielectric tubes are connected to the upper surfaces of the electrodes, respectively, and are respectively provided on the same circumference centered on the central axis of the coaxial tube in a plan view.

3. The plasma processing apparatus according to claim 1 or 2, wherein: The coaxial conductor includes a protrusion having an annular shape in a plan view and protruding inward from the outer conductor of the coaxial conductor.

4. The plasma processing apparatus according to claim 3, wherein: A resonator is provided, the resonator being connected to the side of the coaxial tube opposite to the expanded diameter portion, The resonator is introduced with high-frequency waves from the side.

5. The plasma processing apparatus according to claim 4, wherein: When the frequency of the high-frequency wave is set to f, the distance Δ between the protrusion and the resonator satisfies 4*(220×10 6 ) / f≤Δ≤85*(220×10 6 ) / f, where the unit of distance Δ is mm and the unit of f is Hz.

6. The plasma processing apparatus according to claim 3, wherein: When the frequency of the high-frequency wave is set to f, the distance d between the inner conductor of the coaxial tube and the protrusion satisfies 2*(220×10 6 ) / f≤d≤24*(220×10 6 ) / f, where the unit of distance d is mm and the unit of f is Hz.

7. The plasma processing apparatus according to claim 1 or 2, wherein: The inner conductor of the coaxial tube serves as a gas supply pipe for supplying plasma-generated gas to the electrode.

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