Film forming device

Abstract

To provide a film deposition device capable of depositing a film on a treatment surface of a workpiece material more quickly than conventional, and forming a coating in a wider range more uniformly and at higher quality than conventional.SOLUTION: A film deposition device 1 comprises a treatment vessel 2, a gas supply part 5, an introduction member 22, a microwave supply part 9, a voltage application part 20, a connection member, a sheath enlargement electrode 30, an insulation member 24, and a leakage restraining member 4. The sheath enlargement electrode 30 is arranged around the introduction member 22. The voltage application part 20 applies positive bias voltage for enlarging a sheath layer along the treatment surface 10 of the workpiece material 8 to the sheath enlargement electrode 30. The insulation member 24 is arranged between the sheath enlargement electrode 30 and the treatment vessel 2, and electrically insulates the sheath enlargement electrode 30 from the treatment vessel 2. The leakage restraining member 4 is arranged at a position for being electrically insulated from the workpiece material 8, and has a contact face in contact with the insulation member 24 and an insulation part extending from the contact face to a side away from the insulation member 24.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a film forming apparatus that forms a film on the processing surface of a workpiece using the MVP method (Microwave sheath-Voltage combination Plasma method, high-density excitation plasma method).

Background Art

[0002] An apparatus for forming a film on the processing surface of a conductive workpiece such as a steel material is known. For example, the film forming apparatus described in Patent Document 1 includes a microwave supply unit, a negative voltage application unit, a negative voltage application terminal member, and an auxiliary electrode. The microwave supply unit generates plasma along the processing surface of the conductive workpiece. The negative voltage application unit applies a negative bias voltage to the workpiece to expand the sheath layer along the processing surface of the workpiece. The microwave supply port propagates the microwave supplied from the microwave supply unit to the expanded sheath layer. The negative voltage application terminal member applies the negative bias voltage applied by the negative voltage application unit to the workpiece protruding with respect to the microwave supply port. The auxiliary electrode expands the thickness of the sheath layer formed on the side opposite to the microwave supply port side. The auxiliary electrode is connected to the GND, or a positive voltage supplied from the positive voltage application unit is applied, and is disposed around the outside of the protruding workpiece. The film forming apparatus expands the thickness of the sheath layer on the side opposite to the microwave supply port side to reduce the attenuation of the plasma density and reduce the decrease in the film forming speed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventional film deposition equipment applies a negative bias voltage to the workpiece. Therefore, when forming a film of a material with relatively low conductivity, such as diamond, abnormal discharge (so-called arcing phenomenon) occurs within the deposition equipment, making it impossible to form a film of good quality.

[0005] The object of the present invention is to provide a film deposition apparatus that can perform film deposition on the surface of a workpiece at a faster speed than conventional methods, and can form a uniform and high-quality film over a wider area than conventional methods. [Means for solving the problem]

[0006] The film deposition apparatus according to claim 1 of the present invention comprises: a processing container for containing a conductive workpiece; a gas supply unit for supplying gas to the processing container; an introduction member provided around the workpiece and for introducing microwaves; a microwave supply unit for supplying microwaves from the introduction member to the workpiece for generating plasma along the processing surface of the workpiece; a sheath expansion electrode disposed around the introduction member; a voltage application unit for applying a positive bias voltage to the sheath expansion electrode to expand the sheath layer along the processing surface of the workpiece; a grounding member for electrically connecting the workpiece to the same potential as the ground potential of the voltage application unit; an insulating member disposed between the sheath expansion electrode and the processing container for electrically insulating the sheath expansion electrode and the processing container; and a leakage suppression member disposed in a position electrically insulated from the workpiece and having a contact surface that contacts the insulating member and an insulating portion extending away from the contact surface toward the insulating member. The film deposition apparatus can perform film deposition using the known MVP method (Microwave sheath-Voltage combination Plasma method, high-density excited plasma method), in which a microwave supply unit supplies microwaves and a voltage application unit applies a bias voltage to propagate microwaves across the workpiece surface and generate a high-density plasma near the workpiece. The film deposition apparatus can suppress the occurrence of arcing phenomena and form a high-quality film by using a grounding member to bring the potential of the workpiece to ground potential. The film deposition apparatus is equipped with a leakage suppression member, which reduces the leakage of microwaves from the end face of the insulating member into the processing container. Therefore, the film deposition apparatus can suppress situations in which plasma discharge occurs in unintended areas or where the insulating member is damaged, resulting in a loss of insulation between the sheath expansion electrode and the processing container, due to microwave leakage. The film deposition apparatus can increase the thickness of the sheath layer formed on the processing surface of the workpiece by applying a positive bias voltage to the sheath expansion electrode, thereby forming a uniform film on the processing surface.

[0007] The insulating portion of the film-forming apparatus according to claim 2 of the present invention is formed in an annular shape on the contact surface that surrounds the workpiece. Compared to the case in which the insulating portion is not formed in an annular shape that surrounds the workpiece, the film-forming apparatus according to claim 2 can reduce microwave leakage from the end face of the insulating member into the processing container in the circumferential direction around the workpiece.

[0008] The first length of the insulating part in the direction perpendicular to the contact surface of the film-forming apparatus according to claim 3 of the present invention is within a range of ±1 mm of the second length, which is 1 / 4 of the wavelength of the microwave or an even multiple of the wavelength of the microwave. In the film-forming apparatus according to claim 3, the phase of the microwaves propagated from the insulating member to the insulating part and subsequently reflected is near the opposite of the phase of the microwaves propagating through the insulating member. Therefore, the film-forming apparatus can reduce microwave leakage from the end face of the insulating member into the processing container by canceling out the microwaves propagating through the insulating member with the microwaves propagated from the insulating member to the insulating part and subsequently reflected.

[0009] The film deposition apparatus according to claim 4 of the present invention has a length such that half of the outer diameter of the contact surface of the leakage suppression member is 30 mm or more, and the member is positioned at a distance from the processing container. Compared to the case where half of the outer diameter of the contact surface of the leakage suppression member is less than 30 mm, the film deposition apparatus according to claim 4 can reduce microwave leakage from the end face of the insulating member into the processing container.

[0010] The insulating portion of the film-forming apparatus according to claim 5 of the present invention is a recess extending away from the contact surface toward the insulating member, and the leakage suppression member has a through hole that connects the insulating portion with the space inside the processing container. The film-forming apparatus according to claim 5 can suppress the retention of unintended gases such as air in the insulating portion during film-forming and shorten the exhaust time inside the processing container.

[0011] The film deposition apparatus according to claim 6 of the present invention has a plurality of insulating portions with different outer diameters formed on the contact surface of the leakage suppression member. Compared to the case in which a single insulating portion surrounding the workpiece is formed on the contact surface of the leakage suppression member, the film deposition apparatus according to claim 6 can suppress microwave leakage from the end face of the insulating member into the processing container.

[0012] The outer diameter of the insulating member in the film deposition apparatus according to claim 7 of the present invention is larger than the outer diameter of the contact surface of the leakage suppression member. Compared to the case where the outer diameter of the insulating member is less than or equal to the outer diameter of the contact surface of the leakage suppression member, the film deposition apparatus according to claim 7 can suppress microwave leakage from the end face of the insulating member into the processing container. [Brief explanation of the drawing]

[0013] [Figure 1] This diagram shows the schematic configuration of the film deposition apparatus 1. [Figure 2] This diagram shows the arrangement of the introduction member 22, the workpiece 8, and the sheath expansion electrode 30. [Figure 3] This is a perspective view of the leak suppression member 4. [Figure 4] This is a perspective view of the leak suppression member 4. [Figure 5] This is a cross-sectional view of the leak suppression member 4. [Figure 6] This is a table showing the evaluation test conditions. [Figure 7] This table shows the evaluation test conditions and results. [Figure 8] This graph shows the simulation results illustrating the relationship between the electric field strength (V / m) in the film deposition apparatus 1 and the first length D2 (mm) of the insulating section 42. [Figure 9] This graph shows the simulation results illustrating the relationship between the electric field strength (V / m) in the film deposition apparatus 1 and the width D1 (mm) of the insulating section 42. [Figure 10] This graph shows the simulation results illustrating the relationship between the electric field strength (V / m) in the film deposition apparatus 1 and half (mm) of the outer diameter D4 of the contact surface 41 of the leakage suppression member 4. [Figure 11] This is a perspective view of a modified example of the leakage suppression member 54. [Figure 12] This is a diagram showing the arrangement of the introduction member 22 of the modification example, the work material 8, and the sheath expansion electrode 130.

[0014] Referring to the drawings, a film forming apparatus 1 according to an embodiment of the present invention will be described. In the following description, left - right, front - back, and up - down directions indicated by arrows in the drawings are used. The film forming apparatus 1 is an apparatus that can form a film on a processing surface 10 of a work material 8 using the MVP method disclosed in Japanese Patent Application Laid - Open No. 2004 - 47207. The work material 8 in the present embodiment is rod - shaped, for example, a drill for hole machining. The material of the work material 8 is not particularly limited as long as the processing surface 10, which is the region where the film is to be formed, has conductivity. For example, it is carbide K10. Carbide K10 is a cemented carbide based on the classification described in JIS B 4053:2013. The work material 8 may be a ceramic or resin coated with a conductive material, or may have a metal film formed on its surface by a sputtering method or the like. The processing surface 10 is the region on the surface of the work material 8 that is the target for forming the film. The processing surface 10 is set according to the use of the work material 8. For example, if the work material 8 is a drill, the groove portion of the drill is set as the processing surface 10. For example, if the work material 8 is an end mill, the cutting edge portion of the end mill is set as the processing surface 10.

[0015] As shown in FIGS. 1 and 2, the film forming apparatus 1 includes a processing container 2, an introduction member 22, a cover 23, a sheath expansion electrode 30, an insulating member 24, a leakage suppression member 4, a DC power source 15, a positive voltage pulse generation unit 16, a vacuum pump 3, a pressure adjustment valve 7, a leak valve 33, a gas supply unit 5, a radiation thermometer 29, a control unit 6, and a microwave supply unit 9.

[0016] The processing container 2 is made of metal such as stainless steel and is an airtight container. The processing container 2 is electrically connected to the ground potential (GND). The processing container 2 houses the introduction member 22, the cover 23, the sheath expansion electrode 30, the insulating member 24, and the leakage suppression member 4. The introduction member 22 is provided at the center of the bottom surface of the processing container 2.

[0017] The introduction member 22 is formed of a member such as a dielectric that transmits microwaves, such as quartz, and supplies the microwaves oscillated by the microwave supply unit 9 into the processing container 2. The introduction member 22 has a protruding portion 221 that protrudes toward the inside of the processing container 2 and a base portion 222 that supports the protruding portion 221. A concave portion 223 that is recessed downward is formed on the upper surface of the protruding portion 221, which is the introduction surface 224 of the protruding portion 221. The concave portion 223 is long along the microwave introduction direction J, that is, upward. The outer periphery of the concave portion 223 is slightly larger than the outer periphery of the workpiece 8. When the lower end portion of the workpiece 8 is inserted into the concave portion 223, the lower end portion of the workpiece 8 is surrounded by the protruding portion 221. The extending range of the workpiece 8 in the direction along the introduction direction J, that is, the vertical direction, partially overlaps with the extending range of the protruding portion 221. Thereby, the workpiece 8 is supported by the introduction member 22. The workpiece 8 is disposed inside the processing container 2 in a posture in which the longitudinal direction of the workpiece 8 coincides with the microwave introduction direction J. The film forming apparatus 1 may be provided with a jig that supports the workpiece 8 in the concave portion 223. An electrode 14 is connected to the upper end of the workpiece 8. The upper end of the workpiece 8 is the end portion in the microwave introduction direction J and is the portion farthest from the introduction member 22 within the workpiece 8. The electrode 14 is electrically connected to the ground potential (GND). That is, the potential of the workpiece 8 is the ground potential that is the same potential as the processing container 2. The electrode 14 may be connected to the workpiece 8 below the upper end of the workpiece 8.

[0018] The cover 23 is made of metal and is electrically connected to the processing container 2. The cover 23 may be integrated with the processing container 2 and the processing container 2 may serve as the cover 23. The cover 23 covers the outer peripheral surface of the base portion 222 in a direction other than the microwave introduction direction J, thereby preventing the microwaves from propagating in the radial direction of the workpiece 8. The radial direction of the workpiece 8 is the direction that extends radially away from the axis K of the workpiece 8. The axis K extends in the vertical direction. The cover 23 limits the propagation direction of the microwave pulse transmitted through the introduction member 22 upward.

[0019] The sheath expansion electrode 30 is a cylindrical electrode positioned around the introduction member 22, surrounding the protrusion 221 of the introduction member 22. The sheath expansion electrode 30 is made of a metallic material and is impermeable to gas. The sheath expansion electrode 30 is electrically connected to the positive voltage pulse generation unit 16, and a positive bias voltage pulse is applied. The vertical length of the sheath expansion electrode 30 is limited to the range in which the sheath expansion electrode 30 fits within the processing container 2, and a vertical length of 5 mm or more is preferable. If the vertical length of the sheath expansion electrode 30 is less than 5 mm, the plasma may pass over the sheath expansion electrode 30, and a film may be formed below the introduction surface 224. The vertical length D6 of the sheath expansion electrode 30 is set considering that the position of the upper end 31 of the sheath expansion electrode 30 is the same as the position of the lower end of the processing surface 10 on the introduction member 22 side. In this embodiment, the upper end 31 of the sheathed expanding electrode 30 is positioned above the introduction surface 224 of the protruding portion 221 of the introduction member 22 in the vertical direction. As a result, the introduction surface 224 is surrounded by the sheathed expanding electrode 30 and the workpiece 8, making it difficult for the raw material gas to reach it, and thus preventing contamination of the introduction surface 224 during the film formation process. The lower end of the sheathed expanding electrode 30 is positioned above the cover 23 that covers the base portion 222.

[0020] The insulating member 24 is provided between the cover 23 and the lower end of the sheath expansion electrode 30. The insulating member 24 surrounds the protrusion 221 and is disc-shaped with thickness in the direction J of microwave pulse introduction. The insulating member 24 electrically insulates the sheath expansion electrode 30 from the cover 23 and the processing container 2. The thickness of the insulating member 24 is 1 / 4 or less of the wavelength of the microwave pulse and is a thickness that does not cause dielectric breakdown when power is applied; in this embodiment, the thickness is 0.125 mm. This configuration prevents microwave pulses that pass through the introduction member 22 from passing through the insulating member 24 between the cover 23 and the sheath expansion electrode 30 and leaking into the processing container 2 in a direction different from the introduction direction J. In this embodiment, polyimide was used for the insulating member 24, but it is not limited to this.

[0021] The leak suppression member 4 is positioned in a location electrically insulated from the workpiece 8. The leak suppression member 4 is cylindrical, extending vertically and having a cavity 47 in the center. The workpiece 8 and the sheath expansion electrode 30 are placed in the cavity 47 of the leak suppression member 4. The leak suppression member 4 and the sheath expansion electrode 30 may be positioned to be electrically at the same potential. The outer circumference of the lower end of the workpiece 8 is surrounded by the introduction member 22 and the leak suppression member 4. At least the surface of the leak suppression member 4 that is exposed to other members is made of a conductive material such as stainless steel. In this embodiment, the entire leak suppression member 4 is made of stainless steel. The leak suppression member 4 has an inner flange portion 45, an outer flange portion 46, a contact surface 41 that abuts against the insulating member 24, and an inner circumferential surface 44. The inner flange portion 45 protrudes toward the axis K at the lower end of the leak suppression member 4. The outer flange portion 46 protrudes radially from the lower end of the leakage suppression member 4, away from the axis K. In this embodiment, the contact surface 41 is the lower surface of the leakage suppression member 4. An insulating portion 42 is formed on the contact surface 41, which is a recessed portion that is recessed on the side away from the insulating member 24, i.e., on the upper side. The insulating portion 42 is formed in an annular shape on the contact surface 41, surrounding the workpiece material 8, and the surface of the insulating portion 42 is conductive.

[0022] The first length D2 of the insulating portion 42 in the direction perpendicular to the contact surface 41 is a length within ±1 (mm) of the second length. The first length D2 is the vertical length of the insulating portion 42. The second length is 1 / 4 of the wavelength of the microwave introduced into the processing container 2 from the introduction member 22, or an even multiple of the microwave wavelength. For example, if the microwave frequency is 2.45 (GHz), the microwave wavelength is approximately 122 (mm). In this case, the first length D2 is preferably in the range of ±1 (mm) of 30.5 (mm), which is 1 / 4 of the microwave wavelength, i.e., from 29.5 (mm) to 31.5 (mm). In this case, the insulating portion 42 functions as a choke structure that prevents microwaves from leaking from the insulating member 24 into the space inside the processing container 2.

[0023] On the contact surface 41, the width D1 of the insulating portion 42 in the radial direction of the workpiece material 8 is preferably within the range of 7 / 60 or less of the microwave wavelength. For example, if the microwave frequency is 2.45 (GHz), the width D1 of the insulating portion 42 is preferably 14 (mm) or less.

[0024] The outer diameter D5 of the insulating member 24 is larger than the outer diameter D4 of the contact surface 41 of the leakage suppression member 4. The entire surface of the contact surface 41 is in contact with the insulating member 24. The outer contour of the contact surface 41 is circular in plan view. The outer diameter D4 of the contact surface 41 is preferably 1 / 2 or more of the wavelength of the microwave. For example, if the microwave frequency is 2.45 (GHz), the radius of the outer contour of the contact surface 41, which is 1 / 2 of the outer diameter D4 of the contact surface 41, is preferably 30 (mm) or more and is positioned at a distance from the processing container 2. If the planar shape of the contact surface 41 is not circular, it is preferable that the distance between the position on the outer circumference of the contact surface 41 closest to the workpiece 8 and the center of the workpiece 8 is 30 (mm) or more. Even if the center of the outer contour of the circular contact surface 41 in plan view is different from the center of the workpiece 8, it is preferable that the distance between the position on the outer circumference of the contact surface 41 closest to the workpiece 8 and the center of the workpiece 8 is 30 mm or more.

[0025] The inner circumferential surface 44 is the inner circumferential surface of the inner flange portion 45 of the leak suppression member 4. The inner circumferential surface 44 is in contact with the sheath expanding electrode 30. The leak suppression member 4 has a through hole 43 that connects the insulating portion 42 with the space inside the processing container 2. The through hole 43 is formed in a circular shape in plan view on the upper surface of the leak suppression member 4. The through hole 43 extends upward from the upper end of the insulating portion 42.

[0026] The voltage application unit 20 applies a positive bias voltage to the sheath expansion electrode 30 to expand the sheath layer along the processing surface 10 of the workpiece 8. If the sheath expansion electrode 30 and the leakage suppression member 4 are arranged to be electrically at the same potential, the positive bias voltage may be applied to the leakage suppression member 4. The voltage application unit 20 includes a DC power supply 15 and a positive voltage pulse generation unit 16. The DC power supply 15 supplies a positive bias voltage to the positive voltage pulse generation unit 16 according to the instructions of the control unit 6. The negative terminal of the DC power supply 15 is electrically connected to ground potential (GND). The positive voltage pulse generation unit 16 pulses the positive bias voltage supplied from the DC power supply 15. This pulsation process is a process in which the positive voltage pulse generation unit 16 controls the magnitude, period, and duty cycle of the positive bias voltage pulse according to the instructions of the control unit 6. The positive bias voltage is, for example, a bias voltage in the range of +300 to +390 (V). The voltage application unit 20 of the film deposition apparatus 1 does not include a positive voltage pulse generation unit 16, and a continuous positive bias voltage may be applied to the sheath expansion electrode 30 from a DC power supply 15. The vacuum pump 3 is a pump capable of vacuuming the inside of the processing container 2 via a pressure adjustment valve 7.

[0027] The gas supply unit 5 supplies raw material gas for film formation into the processing container 2. For example, a mass flow controller (MFC) is used for the gas supply unit 5. The raw material gas includes, for example, hydrocarbons such as CH4 and C2H2, and hydrogen gas (H2), while the inert gas includes, for example, nitrogen gas (N2). Under the control of the gas supply unit 5, the gases are appropriately mixed and supplied into the processing container 2. Although not shown, an inert gas may also be supplied into the processing container 2.

[0028] The radiation thermometer 29 is positioned near the outside of the window 27 provided in the side wall of the processing container 2. The radiation thermometer 29 is electrically connected to the control unit 6. The radiation thermometer 29 receives infrared radiation and calculates the intensity of the received infrared radiation. From the calculated infrared radiation intensity, the radiation thermometer 29 calculates the surface temperature of the workpiece 8 and outputs the temperature information of the workpiece 8 to the control unit 6.

[0029] The control unit 6 is responsible for controlling the entire device. The control unit 6 includes a CPU, ROM, and RAM. The control unit 6 outputs control signals to the microwave supply unit 9 and the voltage application unit 20 to control the applied power of the microwave pulse and the applied voltage of the positive voltage pulse. After confirming that the output temperature input from the radiation thermometer 29 is below a preset upper limit temperature, the control unit 6 outputs control signals to the positive voltage pulse generation unit 16 and the microwave pulse control unit 11. If the temperature is above the upper limit temperature, the control unit 6 stops outputting control signals and waits until the temperature falls below the upper limit temperature through natural cooling. The control unit 6 controls the application timing and supply voltage of the bias voltage pulse, and the supply timing and supply power of the microwave pulse generated from the microwave oscillator 12. The control unit 6 outputs a flow rate control signal to the gas supply unit 5 to control the supply of raw material gas and inert gas. The processing container 2 has a vacuum gauge 26 that outputs a pressure signal representing the pressure inside the processing container 2. The control unit 6 controls the pressure inside the processing container 2 by outputting control signals to the pressure regulating valve 7 and the leak valve 33 based on the pressure signal input from the vacuum gauge 26.

[0030] The microwave supply unit 9 supplies microwaves from the introduction member 22 to the workpiece 8 to generate plasma along the processing surface 10 of the workpiece 8. The microwave supply unit 9 comprises a microwave pulse control unit 11, a microwave oscillator 12, a microwave power supply 13, an isolator 17, a tuner 18, a waveguide 19, and a coaxial waveguide 21. The microwave pulse control unit 11 supplies a pulse signal to the microwave power supply 13 according to the instructions of the control unit 6. The microwave power supply 13 supplies power to the microwave oscillator 12 according to the instructions of the control unit 6. The microwave oscillator 12 oscillates pulsed 2.45 (GHz) microwaves according to the instructions of the control unit 6 and supplies microwave pulses to the isolator 17. The microwave pulses are supplied from the microwave oscillator 12 to the processing surface 10 of the workpiece 8 via the isolator 17, tuner 18, waveguide 19, coaxial waveguide 21, and introduction member 22. In this embodiment, the microwave oscillator 12 oscillates pulsed microwaves, but it is not limited to this; it may also continuously output unpulsed microwaves.

[0031] The isolator 17 prevents reflected microwave waves from returning to the microwave oscillator 12. The tuner 18 matches the impedance before and after the tuner 18 so that the reflected microwave waves are minimized. The coaxial waveguide 21 is cylindrically projected upward from the waveguide 19 via a coaxial waveguide converter (not shown) and engages with the base 222 and the bottom surface. The axis of the coaxial waveguide 21 coincides with the axis K of the workpiece 8 supported by the introduction member 22.

[0032] The surface wave-excited plasma generated when performing the MVP method using the above-described film deposition apparatus 1 will now be explained. Normally, when generating surface wave-excited plasma, microwaves are supplied along the interface between a plasma with an electron (ion) density above a certain level and a dielectric material in contact with the plasma. The supplied microwaves propagate as surface waves with the electromagnetic wave energy concentrated at the interface between the plasma and the dielectric material. As a result, the plasma in contact with the interface is excited and further amplified by the high-energy-density surface waves. This generates and maintains a high-density plasma. However, if this dielectric material is replaced with a conductive workpiece material 8, the workpiece material 8 does not function as a waveguide for surface waves, and desirable surface wave propagation and plasma excitation cannot be produced.

[0033] On the other hand, a layer of charged particles with essentially single polarity, a so-called sheath layer, is formed near the surface of an object in contact with the plasma. In the case of a workpiece 8 connected to ground potential, the sheath layer is a layer with low electron density, i.e., positive polarity, and has a relative permittivity ε ≈ 1 in the microwave frequency band. Therefore, by providing a sheath expansion electrode 30 around the lower end of the workpiece 8, connecting the workpiece 8 to ground potential, and applying a positive bias voltage higher than ground potential to the sheath expansion electrode 30, the sheath thickness of the sheath layer formed along the processed surface 10 of the workpiece 8 increases, i.e., the sheath layer expands. This sheath layer acts as a dielectric that propagates surface waves at the interface between the plasma and the object in contact with the plasma. The positive bias voltage applied to the sheath expansion electrode 30 is set so that the potential difference with ground potential is lower than the potential difference required for plasma generation.

[0034] Therefore, microwaves are supplied from an introduction member 22 positioned close to one end of the workpiece 8 toward the other end of the workpiece 8, along the processing surface 10 of the workpiece 8. A positive bias voltage is applied to the sheath expansion electrode 30 positioned around the workpiece 8 and the introduction member 22, and the workpiece 8 is connected to ground potential. As a result, the microwaves propagate as surface waves along the interface between the sheath layer and the plasma. Consequently, a high-density excited plasma based on surface waves is generated along the processing surface 10 of the workpiece 8. This high-density excited plasma is the surface wave excited plasma described above.

[0035] In the MVP method using the film deposition apparatus 1 of the above embodiment, the workpiece 8 is placed in close contact with the introduction member 22, and a sheath layer is formed along the processing surface 10 of the workpiece 8. The workpiece 8 is connected to ground potential, and a sheath expansion electrode 30 is placed around the introduction member 22 where the lower end of the workpiece 8 is placed, and a positive bias voltage is applied. This generates a high-density plasma by microwaves propagating as surface waves along the expanded sheath layer. Because the density of this plasma is high, the workpiece 8 is deposited at high speed. Since the workpiece 8 is positioned opposite the central conductor of the coaxial waveguide 21, microwaves propagate efficiently upward.

[0036] A brief explanation of the film deposition process using the MVP method is provided below. The operator or automated conveyor inserts the workpiece 8 into the recess 223 of the processing container 2, sets the workpiece 8 in the processing container 2, connects the electrode 14 to the upper end of the workpiece 8 to ground potential, and seals the processing container 2. The control unit 6 starts the vacuum pump 3, sets the pressure adjustment valve 7 to fully open, and evacuates the inside of the processing container 2 until a predetermined vacuum level is reached, based on the pressure signal input from the vacuum gauge 26.

[0037] The control unit 6 controls the gas supply unit 5 and the pressure adjustment valve 7 to supply inert gas and raw material gas to the processing container 2 until the pressure inside the processing container 2 reaches a predetermined value. The control unit 6 controls the microwave oscillator 12 when the output temperature input from the radiation thermometer 29 is below the upper limit temperature to generate microwave pulses with a microwave power of 2.45 (GHz), and supplies the generated microwave pulses to the processing surface 10 of the workpiece 8 via the isolator 17, tuner 18, waveguide 19, coaxial waveguide 21, and introduction member 22. The microwave frequency can be between 0.3 and 50 (GHz), for example, 2.45 (GHz). The microwave may be pulsed microwave pulses or continuous microwaves.

[0038] The film deposition apparatus 1 forms a film on the processing surface 10 of the workpiece material 8 that protrudes into the processing container 2 beyond the upper end 31 of the sheath expansion electrode 30. When hydrocarbon gas is used as the raw material gas, various carbides with different structures, such as graphite, diamond, and carbon nanotubes (CNTs), are generated by the plasma. Graphite and CNTs attached to the workpiece material 8 are selectively etched by the hydrogen plasma, so a thin diamond film is formed on the surface of the workpiece material 8. Diamond is non-conductive, and when a negative bias voltage is applied to the workpiece material 8 as in conventional technology, electric charge accumulates on the diamond surface. This causes abnormal discharge (arking phenomenon) due to the potential difference between the accumulated charge and the workpiece material 8, destroying the diamond film. The film deposition apparatus 1 of this embodiment reduces the potential difference with the accumulated charge by setting the potential of the workpiece material 8 to ground potential, thereby suppressing the occurrence of the arcing phenomenon, preventing the destruction of the diamond film, and enabling the formation of a high-quality diamond film.

[0039] The control unit 6 quickly exhausts the raw material gas and inert gas remaining in the processing container 2 using the vacuum pump 3, and then fully closes the pressure adjustment valve 7. Subsequently, the control unit 6 opens the leak valve 33, and when the pressure inside the processing container 2 becomes equal to the ambient pressure, it notifies the liquid crystal display (LCD) or other notification unit that the film deposition process is complete, and terminates the film deposition process. The operator or automated conveyor removes the electrodes 14 from the workpiece 8 and removes the workpiece 8, on which a film has been formed on the processed surface 10, from the processing container 2.

[0040] The evaluation test results will be explained with reference to Figures 6 and 7. The workpiece material 8 was a cutting tool made of carbide K10 with a diameter of 10 mm, a total length of 85 mm, and a groove length of 50 mm. A film deposition apparatus 1 without a leakage suppression member 4 was used as a comparative example, and a film deposition apparatus 1 equipped with a leakage suppression member 4 was used as an example. The processing surface 10 was set to an area from the tip of the workpiece material 8 to 50 mm. As shown in Figure 6, the microwaves oscillated by the microwave oscillator 12 of the film deposition apparatus 1 were controlled to have a peak power of 500 to 1000 W, a frequency of 1 kHz, and a duty cycle of 50%. The bias voltage pulse was controlled to have a frequency of 1 kHz and a peak voltage value of 200 to 390 V. The gas flow rate was supplied at 200 sccm for H2 and 2 sccm for CH4, and the pressure was controlled to 1 kPa. The comparative example and the example were both tested under the same conditions, and the presence or absence of microwave-derived plasma leakage near the insulating member 24 was visually confirmed. In Figure 7, white circles indicate cases where plasma generation was not confirmed, and crosses indicate cases where plasma generation was confirmed.

[0041] As shown in Figure 7, in the comparative example, plasma generation was confirmed under two conditions: when the microwave peak power was 500W and the bias voltage pulse peak voltage was 370V or 390V, and when the microwave peak power was 1000W and the bias voltage pulse peak voltage was 370V. Plasma generation was not confirmed under the other conditions in the comparative example. On the other hand, in the embodiment, plasma generation was not confirmed under any conditions. From the above, it was confirmed that microwave leakage can be suppressed by arranging the leakage suppression member 4.

[0042] Referring to Figures 8 to 10, the simulation results confirming the effect of microwave leakage from the insulating member 24 on the structure of the leakage suppression member 4 are explained. The simulator used COMSOL® Multiphysics 6.0 finite element analysis software with an RF module. The microwave frequency was set to 2.45 GHz, and the frequency domain analysis was performed. In the model, the relative permittivity, non-permeability, and conductivity of the workpiece material 8, introduction member 22, and insulating member 24 were set. The plasma pressure was set to 50 Pa, and the plasma density to 1E17 (1 / m³). 3 The dielectric constant and conductivity were calculated assuming an electron temperature of 2 (eV). For each of the structures of the leakage suppression member 4, specifically the first length D2 (mm) of the insulating part 42, the width D1 (mm) of the insulating part 42, and 1 / 2 (mm) of the outer diameter D4 of the contact surface 41, the conditions under which plasma does not occur were determined based on simulation results. The minimum electric field strength required to maintain plasma discharge is said to be half of the dielectric breakdown voltage, and from a known document (Analysis of hydrogen plasma in a microwave plasma chemical vapor deposition reactor, G. Shivkumar et al., Journal of Applied Physics 119, 113301, 2016), the condition of 7500 (V / m) at 1.33 (kPa) was adopted. That is, it is assumed that plasma will not occur under conditions where the electric field strength is 7500 (V / m) or less. The electric field strength was calculated using a known simulator when the first length D2 (mm) of the insulating part 42, the width D1 (mm) of the insulating part 42, and half (mm) of the outer diameter D4 of the contact surface 41 were varied. The inner diameter of the insulating part 42 was set to 36 (mm), and the height D3 of the leakage suppression member 4 was set to 32.6 (mm). The thick lines in Figures 8 to 10 indicate an electric field strength threshold of 7500 (V / m).

[0043] In the simulations shown in Figure 8 regarding the electric field strength (V / m) and the first length D2 (mm) of the insulating part 42, the width D1 of the insulating part 42 was set to 8 (mm), and half of the outer diameter D4 of the contact surface 41 was set to 36 (mm). As shown in Figure 8, under the condition that the first length D2 of the insulating part 42 was 29.6 (mm), the electric field strength was 7124 (V / m), under the condition that it was 30.6 (mm), the electric field strength was 1944 (V / m), and under the condition that it was 31.6 (mm), the electric field strength was 3233 (V / m), all of which were below 7500 (V / m). When the first length D2 of the insulating portion 42 was 28.6 mm, the electric field strength was 12367 V / m, and when the first length D2 of the insulating portion 42 was 32.6 mm, the electric field strength was 8431 V / m, both exceeding 7500 V / m. From the above, it was suggested that when the first length D2 of the insulating portion 42 is within ±1 mm of the second length, the generation of plasma caused by microwaves leaked from the insulating member 24 can be suitably suppressed.

[0044] In the simulations shown in Figure 9 regarding the electric field strength (V / m) and the width D1 (mm) of the insulating part 42, the first length D2 of the insulating part 42 was set to 30.6 (mm), and half of the outer diameter D4 of the contact surface 41 was set to 36 (mm). As shown in Figure 9, under the condition that the width D1 of the insulating part 42 was 12 (mm) or less, the electric field strength was below 7500 (V / m), and under the condition that the width D1 of the insulating part 42 was 1 (mm) or more, a monotonically increasing trend was observed between the width D1 of the insulating part 42 and the electric field strength. Under the condition that the width D1 of the insulating part 42 was 14 (mm), the electric field strength was 7543 (V / m), and under the condition that the width D1 of the insulating part 42 was 16 (mm), it was 8697 (V / m). From the above, it was suggested that when the width D1 of the insulating part 42 is 14 (mm) or less, the generation of plasma caused by microwaves leaking from the insulating member 24 can be suitably suppressed.

[0045] In the simulation showing the electric field strength (V / m) and half the outer diameter D4 (mm) of the contact surface 41 of the leakage suppression member 4 in Figure 10, the first length D2 of the insulating part 42 was set to 30.6 mm and the width D1 of the insulating part 42 was set to 8 mm. As shown in Figure 10, under the condition that half the outer diameter D4 of the contact surface 41 was 28 mm or more, a monotonically decreasing trend was observed between half the outer diameter D4 of the contact surface 41 and the electric field strength. Under the condition that half the outer diameter D4 of the contact surface 41 was 29 mm or less, the electric field strength exceeded 7500 V / m, under the condition that half the outer diameter D4 of the contact surface 41 was 29 mm, the electric field strength was 8136 V / m, and under the condition that half the outer diameter D4 of the contact surface 41 was 30 mm, it was 7452 V / m. From the above, it is suggested that the generation of plasma caused by microwaves leaking from the insulating member 24 can be effectively suppressed when half of the outer diameter D4 of the contact surface 41 of the leakage suppression member 4 is 30 mm or more, and the member is positioned at a distance from the processing container 2.

[0046] A modified film deposition apparatus 1 will be described with reference to Figures 11 and 12. In Figures 11 and 12, the same reference numerals are used for components similar to those in the film deposition apparatus 1 of the above embodiment. The modified film deposition apparatus 1 differs from the film deposition apparatus 1 of the above embodiment in that it includes an introduction member 122, a sheath expanding electrode 130, and a leak suppression member 54 instead of the introduction member 22, the sheath expanding electrode 30, and the leak suppression member 4, while other components are the same as those in the film deposition apparatus 1 of the above embodiment. The introduction member 122, the sheath expanding electrode 130, and the leak suppression member 54 will be described below. The introduction member 122 of the modified embodiment has a protruding portion 225 that protrudes toward the processing container 2 and a base portion 222 that supports the protruding portion 225. The protruding portion 225 has a recess 227 formed inward from the introduction surface 226, which is the upper surface of the protruding portion 225. The recess 228 is long in the direction along the microwave introduction direction J, i.e., upward. The outer circumference of the recess 227 is slightly larger than the outer circumference of the workpiece 8. The upper end 131 of the sheath expanding electrode 130 is below the introduction surface 226 of the introduction member 122. When the upper end 131 of the sheath expanding electrode 130 is below the introduction surface 226 in the protruding direction, the workpiece 8 is covered by the protruding portion 225 in the range from the position of the upper end 131 in the protruding direction to the position of the introduction surface 226, so no coating is formed, but a coating of sufficient quality can be formed above the introduction surface 226. The upper end 131 of the sheath expanding electrode 130 may also be at the same position as the introduction surface 226 of the introduction member 122 in the vertical direction.

[0047] The leak suppression member 54 is positioned in a location electrically insulated from the workpiece 8. The leak suppression member 54 is cylindrical, extending vertically and having a cavity 47 in the center. The workpiece 8 and the sheath expansion electrode 130 are placed in the cavity 47. The leak suppression member 54 has a contact surface 51 that abuts against the insulating member 24 and an inner circumferential surface 44 similar to that of the above embodiment. At least the surface of the leak suppression member 54 is made of a conductive material such as stainless steel. In this embodiment, the entire leak suppression member 54 is made of stainless steel. In this embodiment, the contact surface 51 is the lower surface of the leak suppression member 54. Insulating portions 52 and 53 are formed on the contact surface 51, which are recessed portions that are recessed on the side away from the insulating member 24, i.e., on the upper side. The insulating portions 52 and 53 are formed in an annular shape on the contact surface 41, surrounding the workpiece 8. The insulating portions 52 and 53 have different outer diameters. The width and first length of the insulating portions 52 and 53 are the same. The leakage suppression member 54 may have through holes formed in each of the insulating portions 52 and 53 to communicate with the processing container 2.

[0048] In the above embodiment, the film deposition apparatus 1, processing container 2, leakage suppression member 4, gas supply unit 5, workpiece 8, electrode 14, microwave supply unit 9, processing surface 10, introduction member 22, insulating member 24, sheath expanding electrode 30, contact surface 41, insulating part 42, and through hole 43 are examples of the film deposition apparatus, processing container, leakage suppression member, gas supply unit, workpiece, grounding member, microwave supply unit, processing surface, introduction member, insulating member, sheath expanding electrode, contact surface, insulating part, and through hole of the present invention. The voltage application unit 20 is an example of the voltage application unit of the present invention. The introduction member 122, sheath expanding electrode 130, leakage suppression member 54, and contact surface 51 of the modified example are examples of the introduction member, sheath expanding electrode, leakage suppression member, and contact surface of the present invention. The insulating parts 52 and 53 are examples of multiple insulating parts of the present invention.

[0049] The film deposition apparatus 1 of the above embodiment comprises a processing container 2, a gas supply unit 5, a microwave supply unit 9, a sheath expansion electrode 30, a voltage application unit 20, an electrode 14, an insulating member 24, and a leakage suppression member 4. The gas supply unit 5 supplies gas to the processing container 2. The processing container 2 houses a conductive workpiece 8. An introduction member 22 is provided around the processing container 2 and introduces microwaves. The microwave supply unit 9 supplies microwaves from the introduction member 22 to the workpiece 8 to generate plasma along the processing surface 10 of the workpiece 8. The sheath expansion electrode 30 is arranged around the introduction member 22. The voltage application unit 20 applies a positive bias voltage to the sheath expansion electrode 30 to expand the sheath layer along the processing surface 10 of the workpiece 8. The electrode 14 electrically connects the workpiece 8 to the same potential as the ground potential of the voltage application unit 20. The insulating member 24 is positioned between the sheath expansion electrode 30 and the processing container 2, electrically insulating the sheath expansion electrode 30 from the processing container 2. The leakage suppression member 4 is positioned electrically insulated from the workpiece 8 and has a contact surface 41 that contacts the insulating member 24 and an insulating portion 42 that extends from the contact surface 41 away from the insulating member 24. The film deposition apparatus 1 can perform a film deposition process using the known MVP method, in which the microwave supply unit 9 supplies microwaves and the voltage application unit 20 applies a bias voltage, causing microwaves to propagate on the processing surface 10 of the workpiece 8 and generating a high-density plasma near the workpiece 8. The film deposition apparatus 1 can suppress the occurrence of arcing phenomena and form a high-quality film by setting the potential of the workpiece 8 to ground potential using the electrode 14. Since the film deposition apparatus 1 is equipped with the leakage suppression member 4, leakage of microwaves into the processing container 2 from the end face of the insulating member 24 can be reduced. Therefore, the film deposition apparatus 1 can suppress situations in which plasma discharge occurs in unintended areas due to microwave leakage, or where the insulating member 24 is damaged, resulting in a loss of insulation between the sheath expansion electrode 30 and the processing container 2. By applying a positive bias voltage to the sheath expansion electrode 30, the film deposition apparatus 1 can increase the thickness of the sheath layer formed on the processing surface 10 of the workpiece 8, thereby forming a uniform film on the processing surface 10.

[0050] The insulating portion 42 is formed in an annular shape surrounding the workpiece 8 on the contact surface 41. Compared to a case where the insulating portion 42 is not formed in an annular shape surrounding the workpiece 8, the film deposition apparatus 1 can reduce microwave leakage from the end face of the insulating member 24 into the processing container 2 in the circumferential direction around the workpiece 8.

[0051] The first length D2 of the insulating portion 42 in the direction perpendicular to the contact surface 41 is a length within ±1 (mm) of the second length, which is 1 / 4 of the wavelength of the microwave or an even multiple of the wavelength of the microwave. In the film deposition apparatus 1, the phase of the microwaves propagated from the insulating member 24 to the insulating portion 42 and then reflected is near the opposite phase of the microwaves propagating through the insulating member 24. Therefore, the film deposition apparatus 1 can reduce microwave leakage into the processing container 2 from the end face of the insulating member 24 by canceling out the microwaves propagating through the insulating member 24 with the microwaves propagated from the insulating member 24 to the insulating portion 42 and then reflected.

[0052] The length of the contact surface 41 of the leakage suppression member 4 is such that half of its outer diameter is 30 mm or more, and it is positioned at a distance from the processing container 2. The film deposition apparatus 1 can reduce microwave leakage from the end face of the insulating member 24 into the processing container 2 compared to the case where half of the outer diameter of the contact surface 41 from the workpiece 8 is less than 30 mm.

[0053] The insulating portion 42 is a recess extending away from the insulating member 24 from the contact surface 41. The leakage suppression member 4 has a through hole 43 that connects the insulating portion 42 to the space inside the processing container 2. When the film deposition apparatus 1 performs film deposition, it can suppress the retention of unintended gases such as air in the insulating portion 42 and shorten the exhaust time inside the processing container 2.

[0054] The outer diameter D5 of the insulating member 24 is larger than the outer diameter D4 of the contact surface 41 of the leakage suppression member 4. The film deposition apparatus 1 can suppress microwave leakage from the end face of the insulating member 24 into the processing container 2 compared to the case where the outer diameter D5 of the insulating member 24 is less than or equal to the outer diameter D4 of the contact surface 41 of the leakage suppression member 4.

[0055] The sheath expansion electrode 30 surrounds the introduction surface 224 of the introduction member 22. Therefore, microwaves introduced from the introduction surface 224 to the workpiece material 8 do not leak outside the sheath expansion electrode 30, and the film deposition apparatus 1 can form a uniform, high-quality film over a wide area at high speed. Film is not deposited on the area surrounding the introduction member 22 that is surrounded by the sheath expansion electrode 30. Therefore, by setting the position of the upper end 31 of the sheath expansion electrode 30, the film deposition apparatus 1 can reliably perform film deposition on the processing surface 10. By setting the potential of the workpiece material 8 to the ground potential, the film deposition apparatus 1 can suppress the occurrence of arcing, which is a problem when forming films with low conductivity. Therefore, the film deposition apparatus 1 can form films with low conductivity, such as diamond, uniformly, with high quality, and at high speed over a wide area.

[0056] In the modified version, the contact surface 41 of the leakage suppression member 54 has multiple insulating portions 52 and 53 with different outer diameters formed thereon. The film deposition apparatus 1 can suppress microwave leakage into the processing container 2 from the end face of the insulating member 24 compared to the case where a single insulating portion 42 surrounding the workpiece material 8 is formed on the contact surface 41.

[0057] The film deposition apparatus of the present invention can be modified in various ways beyond the above embodiments. The following modifications may be combined as appropriate within a range that does not contradict each other. The workpiece material 8 does not need to be grounded. The leakage suppression member 4 only needs to have conductivity on at least its surface, and may be, for example, a ceramic with a conductive coating on its surface. The planar shapes of the insulating member 24 and the leakage suppression member 4 do not each have to be ring-shaped. The shape, size, and arrangement of the introduction member 22, the sheath expanding electrodes 30, 130, and the leakage suppression members 4, 54 may each be changed as appropriate. The contact surface 41 of the leakage suppression member 4 may be in contact with the lower surface of the insulating member 24. The microwave introduction direction J does not have to be upward, and the arrangement of each member may be changed according to the microwave introduction direction J.

[0058] The shape and size of the insulating portion 42 of the leakage suppression member 4 may be appropriately changed considering the configuration of the introduction member 22, the sheath expanding electrode 30, and the insulating member 24, as well as the film formation conditions of the workpiece material 8. The insulating portion may be a recess extending away from the insulating member 24 from the contact surface 41, or an insulating layer made of an insulating material such as ceramics that extends away from the insulating member 24 from the contact surface 41. The insulating portion 42 of the leakage suppression member 4 does not have to be formed in an annular shape surrounding the workpiece material 8 on the contact surface 41, but may be formed in any shape such as a circle, arc, or line segment in a part of the circumferential direction around the workpiece material 8 on the contact surface 41. The first length D2 of the insulating portion 42 of the leakage suppression member 4 in the direction perpendicular to the contact surface 41 does not have to be within the range of ±1 (mm) of the second length. If multiple insulating parts are formed in the leak suppression member, one insulating part does not have to be formed in an annular shape surrounding the workpiece 8 on the contact surface of the leak suppression member, and the other insulating parts may be formed in an arc shape or a linear shape, and the first lengths of each insulating part may be the same or different. Half of the outer diameter D4 of the contact surface 41 of the leak suppression member 4 may be less than 30 (mm). The leak suppression member 4 does not have to have through holes 43 that connect the insulating part 42 to the space inside the processing container 2. The arrangement, shape, and number of through holes 43 may be changed as appropriate. If multiple insulating parts are formed surrounding the workpiece 8, the number of insulating parts may be changed as appropriate. The outer diameter D5 of the insulating member 24 may be less than or equal to the outer diameter D4 of the contact surface 41 of the leak suppression member 4. [Explanation of symbols]

[0059] 1: Film deposition equipment 2: Processing container 4: Leakage suppression member 5: Gas supply department 8: Processed material 9: Microwave supply unit 10: Treated surface 11: Microwave pulse control unit 12: Microwave Oscillator 13: Microwave power supply 14: Electrode 15 :DC power supply 17: Isolator 18: Tuner 19: Waveguide 20: Voltage application section 21: Coaxial waveguide 22: Introduction component 24: Insulating material 30: Sheath magnifying electrode 41: Contact surface 42: Insulation part 43: Through hole 44: Inner surface 45: Inner flange 46:Outer flange 47: Cavity

Claims

1. A processing container for containing a conductive workpiece, A gas supply unit that supplies gas to the processing container, An introduction member provided around the workpiece and for introducing microwaves, A microwave supply unit that supplies microwaves from the introduction member to the workpiece to generate plasma along the surface of the workpiece, A sheath expansion electrode is arranged around the aforementioned introduction member, A voltage application unit applies a positive bias voltage to the sheath expansion electrode to expand the sheath layer along the processing surface of the workpiece, A grounding member that electrically connects the workpiece to the same potential as the ground potential of the voltage application section, An insulating member is disposed between the sheath expansion electrode and the processing container to electrically insulate the sheath expansion electrode and the processing container, A film deposition apparatus comprising a leakage suppression member that is positioned electrically insulated from the workpiece and has a contact surface that contacts the insulating member, and an insulating portion that extends away from the contact surface toward the insulating member and has at least a conductive surface, thereby suppressing microwave leakage from the insulating member.

2. The film-forming apparatus according to claim 1, characterized in that the insulating portion is formed in an annular shape surrounding the workpiece on the contact surface.

3. The film deposition apparatus according to claim 2, characterized in that the first length of the insulating portion in a direction perpendicular to the contact surface is within a range of ±1 mm of the second length which is 1 / 4 of the wavelength of the microwave or an even multiple of the wavelength of the microwave.

4. The film-forming apparatus according to claim 2 or 3, characterized in that half of the outer diameter of the contact surface of the leakage suppression member is 30 mm or more, and the member is positioned at a distance from the processing container.

5. The insulating portion is a recess extending away from the contact surface toward the insulating member, The film-forming apparatus according to claim 1 or 2, characterized in that the leakage suppression member has a through hole that connects the insulating portion and the space inside the processing container.

6. The film-forming apparatus according to claim 2, characterized in that a plurality of insulating portions having different outer diameters are formed on the contact surface of the leakage suppression member.

7. The film-forming apparatus according to claim 1 or 2, characterized in that the outer diameter of the insulating member is larger than the outer diameter of the contact surface of the leakage suppression member.

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