JP2024067093A - Film forming equipment - Google Patents

Abstract

[Problem] To provide a film forming apparatus capable of performing a film forming process on the processing surface of a workpiece material at a higher speed than conventionally, and capable of forming a uniform, high-quality coating over a wider area than conventionally. [Solution] The film forming apparatus 1 comprises a processing vessel 2, a gas supply unit 5, an introduction member 22, a microwave supply unit 9, a voltage application unit 20, a connection member, a sheath expansion electrode 30, an insulating member 24, and a leakage suppression member 4. The sheath expansion electrode 30 is disposed around the introduction member 22. The voltage application unit 20 applies a positive bias voltage to the sheath expansion electrode 30, which expands a sheath layer along the processing surface 10 of the workpiece material 8. The insulating member 24 is disposed between the sheath expansion electrode 30 and the processing vessel 2, and electrically insulates the sheath expansion electrode 30 from the processing vessel 2. The leakage suppression member 4 is disposed in a position electrically insulated from the workpiece material 8, and has an abutting surface that abuts against the insulating member 24, and an insulating portion that extends from the abutting surface to a side away from the insulating member 24. [Selected Figure] FIG. 1

Description

The present invention relates to a film forming device that uses the MVP method (Microwave sheath-voltage combination plasma method, a high-density excited plasma method) to form a film on the processing surface of a workpiece.

There is known an apparatus for forming a film on the processing surface of a conductive workpiece material such as steel. 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 material. The negative voltage application unit applies a negative bias voltage to the workpiece material, which expands the sheath layer along the processing surface of the workpiece material. The microwave supply port propagates the microwaves 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 material arranged to protrude from the microwave supply port. The auxiliary electrode expands the thickness of the sheath layer formed on the side opposite to the microwave supply port. The auxiliary electrode is connected to GND or is applied with a positive voltage supplied from the positive voltage application unit, and is arranged around the outside of the workpiece material arranged to protrude. The deposition device increases the thickness of the sheath layer on the side opposite the microwave supply port to reduce attenuation of plasma density and reduce the decrease in deposition rate.

JP 2016-69685 A

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

The object of the present invention is to provide a film forming apparatus that can perform film forming processing on the processing surface of a workpiece material faster than conventional methods and can form a uniform, high-quality coating over a wider area than conventional methods.

The film forming apparatus of claim 1 of the present invention includes a processing vessel that contains a conductive workpiece material, a gas supply unit that supplies gas to the processing vessel, an introduction member that is provided around the workpiece material and introduces microwaves, a microwave supply unit that supplies the microwaves from the introduction member to the workpiece material to generate plasma along the processing surface of the workpiece material, a sheath expansion electrode arranged around the introduction member, a voltage application unit that applies a positive bias voltage to the sheath expansion electrode to expand the sheath layer along the processing surface of the workpiece material, a grounding member that electrically connects the workpiece material to the same potential as the ground potential of the voltage application unit, an insulating member that is arranged between the sheath expansion electrode and the processing vessel and electrically insulates the sheath expansion electrode from the processing vessel, and a leakage suppression member that is arranged in a position electrically insulated from the workpiece material and has an abutment surface that abuts the insulating member and an insulating portion that extends from the abutment surface to a side away from the insulating member. The film forming apparatus can perform a film forming process using a known MVP method (Microwave sheath-Voltage combination Plasma method, high density excitation plasma method), in which a microwave supply unit supplies microwaves and a voltage application unit applies a bias voltage to propagate microwaves to the surface of a workpiece, generating high density plasma in the vicinity of the workpiece. The film forming apparatus can suppress the occurrence of arcing and form a high quality film by setting the potential of the workpiece to ground potential using a grounding member. Since the film forming apparatus is provided with a leakage suppression member, it can reduce the leakage of microwaves from the end face of the insulating member into the processing vessel. Therefore, the film forming apparatus can suppress the occurrence of plasma discharge in unintended parts due to microwave leakage, or the occurrence of a situation in which the insulation between the sheath expansion electrode and the processing vessel cannot be maintained due to damage to the insulating member. By applying a positive bias voltage to the sheath expansion electrode, the film-forming device can expand the thickness of the sheath layer formed on the processing surface of the workpiece, forming a uniform coating on the processing surface.

The insulating portion of the film forming apparatus of claim 2 of the present invention is formed in a ring shape surrounding the workpiece material at the contact surface. The film forming apparatus of claim 2 can reduce leakage of microwaves from the end face of the insulating member into the processing vessel in the circumferential direction around the workpiece material, compared to a case in which the insulating portion is not formed in a ring shape surrounding the workpiece material.

The first length in the direction perpendicular to the contact surface of the insulating part of the film forming apparatus of claim 3 of the present invention is a length within the 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 of claim 3, the phase of the microwave propagated from the insulating member to the insulating part and then bouncing back is approximately the opposite of the phase of the microwave propagating through the insulating member. Therefore, the film forming apparatus can reduce the leakage of microwaves from the end face of the insulating member into the processing vessel by canceling out the microwaves propagating through the insulating member with the microwaves propagating from the insulating member to the insulating part and then bouncing back.

In the film forming apparatus of claim 4 of the present invention, 1/2 of the outer diameter of the contact surface of the leakage suppression member is 30 mm or more, and the length is such that the leakage suppression member is disposed at a distance from the processing vessel. The film forming apparatus of claim 4 can reduce the leakage of microwaves from the end face of the insulating member into the processing vessel, compared to when 1/2 of the outer diameter of the contact surface of the leakage suppression member is less than 30 mm.

The insulating portion of the film forming apparatus of claim 5 of the present invention is a recess extending from the contact surface away from the insulating member, and the leakage suppression member has a through hole that communicates the insulating portion with the space inside the processing vessel. The film forming apparatus of claim 5 can suppress unintended gas such as air from remaining in the insulating portion when performing film forming processing, and can shorten the evacuation time inside the processing vessel.

The contact surface of the leakage suppression member of the film forming apparatus of claim 6 of the present invention is formed with a plurality of insulating portions having different outer diameters. The film forming apparatus of claim 6 can suppress leakage of microwaves from the end face of the insulating member into the processing vessel, compared to a case in which a single insulating portion surrounding the workpiece material is formed on the contact surface of the leakage suppression member.

The outer diameter of the insulating member of the film forming apparatus of claim 7 of the present invention is larger than the outer diameter of the contact surface of the leakage suppression member. The film forming apparatus of claim 7 can suppress leakage of microwaves from the end face of the insulating member into the processing vessel, compared to when the outer diameter of the insulating member is equal to or smaller than the outer diameter of the contact surface of the leakage suppression member.

1 is a diagram showing a schematic configuration of a film forming apparatus 1. FIG. 1 is a diagram showing the arrangement of an introduction member 22, a workpiece 8, and a sheath expansion electrode 30. FIG. FIG. 2 is a perspective view of a leakage suppression member 4. FIG. 2 is a perspective view of the leakage suppression member 4. 3 is a cross-sectional view of the leakage suppression member 4. FIG. 1 is a table showing evaluation test conditions. 1 is a table showing evaluation test conditions and results. 11 is a graph showing a simulation result illustrating the relationship between the electric field strength (V/m) and the first length D2 (mm) of the insulating portion 42 in the film forming apparatus 1. 11 is a graph showing a simulation result illustrating the relationship between the electric field strength (V/m) and the width D1 (mm) of the insulating portion 42 in the film forming apparatus 1. 13 is a graph showing a simulation result illustrating the relationship between the electric field strength (V/m) in the film forming apparatus 1 and ½ (mm) of the outer diameter D4 of the contact surface 41 of the leakage suppression member 4. 13 is a perspective view of a leakage suppression member 54 according to a modified example. FIG. 13 is a diagram showing the arrangement of an introduction member 22, a workpiece 8, and a sheath expansion electrode 130 in a modified example. FIG.

The film forming apparatus 1 according to one embodiment of the present invention will be described with reference to the drawings. In the following description, the left and right, front and rear, and up and down directions shown by arrows in the drawings will be used. The film forming apparatus 1 is an apparatus capable of forming a film on the processing surface 10 of the workpiece material 8 using the MVP method disclosed in JP 2004-47207 A. The workpiece material 8 in this embodiment is rod-shaped, for example, a drill for drilling holes. The material of the workpiece material 8 is not particularly limited as long as the processing surface 10, which is the area where the film is formed, is conductive, and is, for example, superhard K10. Superhard K10 is a superhard alloy based on the classification described in JIS B 4053:2013. The workpiece material 8 may be ceramics or resin coated with a conductive material, or a metal film may be formed on the surface by a sputtering method or the like. The processing surface 10 is the area of the surface of the workpiece material 8 on which the film is to be formed. The processing surface 10 is set according to the application of the workpiece material 8. For example, if the workpiece 8 is a drill, the grooves of the drill are set on the treatment surface 10. For example, if the workpiece 8 is an end mill, the cutting edge of the end mill is set on the treatment surface 10.

As shown in Figures 1 and 2, the film forming apparatus 1 includes a processing vessel 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 supply 15, a positive voltage pulse generating 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.

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

The introduction member 22 is formed of a material such as a dielectric material that transmits microwaves, such as quartz, and supplies the microwaves generated by the microwave supply unit 9 into the processing vessel 2. The introduction member 22 has a protrusion 221 that protrudes into the processing vessel 2 and a base 222 that supports the protrusion 221. The protrusion 221 has a recess 223 that is recessed downward from the introduction surface 224, which is the upper surface of the protrusion 221. The recess 223 is long in the introduction direction J of the microwave, that is, in the upward direction. The outer periphery of the recess 223 is slightly larger than the outer periphery of the workpiece 8. When the lower end of the workpiece 8 is inserted into the recess 223, the lower end of the workpiece 8 is covered by the protrusion 221. The extension range of the workpiece 8 in the direction along the introduction direction J, that is, in the vertical direction, partially overlaps with the extension range of the protrusion 221. As a result, the workpiece 8 is supported by the introduction member 22. The workpiece 8 is placed inside the processing vessel 2 in such a position that 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 for supporting the workpiece 8 in the recess 223. The electrode 14 is connected to the upper end of the workpiece 8. The upper end of the workpiece 8 is the end in the microwave introduction direction J, and is the part of the workpiece 8 that is the furthest from the introduction member 22. The electrode 14 is electrically connected to a ground potential (GND). That is, the potential of the workpiece 8 is the same ground potential as the processing vessel 2. The electrode 14 may be connected to the workpiece 8 below the upper end of the workpiece 8.

The cover 23 is made of metal and is electrically connected to the processing vessel 2. The cover 23 may be integral with the processing vessel 2, with the processing vessel 2 fulfilling the role of the cover 23. The cover 23 covers the outer peripheral surface of the base 222 in directions 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 extending 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 that has passed through the introduction member 22 to the upward direction.

The sheath expansion electrode 30 is a cylindrical electrode that surrounds the protrusion 221 of the introduction member 22 and is arranged around the introduction member 22. The sheath expansion electrode 30 is made of a metal material and is gas impermeable. The sheath expansion electrode 30 is electrically connected to the positive voltage pulse generator 16, and a positive bias voltage pulse is applied to the sheath expansion electrode 30. The vertical length of the sheath expansion electrode 30 may be within a range in which the sheath expansion electrode 30 fits within the processing vessel 2, and the vertical length of the sheath expansion electrode 30 is preferably 5 (mm) or more. If the vertical length of the sheath expansion electrode 30 is less than 5 (mm), the plasma may overcome 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 taking into consideration that the position of the upper end 31 of the sheath expansion electrode 30 is the same as the lower end of the processing surface 10 on the introduction member 22 side. In this embodiment, the upper end 31 of the sheath expansion electrode 30 is positioned above the introduction surface 224 of the protrusion 221 of the introduction member 22 in the vertical direction. As a result, the introduction surface 224 is surrounded by the sheath expansion electrode 30 and the material to be processed 8, making it difficult for the raw material gas to reach it, and preventing the introduction surface 224 from becoming dirty during the film formation process. The lower end of the sheath expansion electrode 30 is located above the cover 23 that covers the base 222.

The insulating member 24 is provided between the cover 23 and the lower end of the sheath expansion electrode 30. The insulating member 24 is a disk-shaped member that surrounds the periphery of the protrusion 221 and has a thickness in the introduction direction J of the microwave pulse. The insulating member 24 electrically insulates the sheath expansion electrode 30 from the cover 23 and the processing vessel 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 due to the application of power, and is 0.125 (mm) in the embodiment. With this configuration, the microwave pulse that penetrates the introduction member 22 is prevented from penetrating the insulating member 24 between the cover 23 and the sheath expansion electrode 30 and leaking into the processing vessel 2 in a direction different from the introduction direction J. Note that, although polyimide is used for the insulating member 24 in the embodiment, the present invention is not limited to this.

The leakage suppression member 4 is arranged at a position electrically insulated from the workpiece material 8. The leakage suppression member 4 is cylindrical, extending in the vertical direction and having a cavity 47 in the center. The leakage suppression member 4 arranges the workpiece material 8 and the sheath expansion electrode 30 in the cavity 47. The leakage suppression member 4 and the sheath expansion electrode 30 may be arranged so as to be electrically at the same potential. The outer periphery of the lower end of the workpiece material 8 is surrounded by the introduction member 22 and the leakage suppression member 4. At least the surface of the leakage suppression member 4 that is exposed to other members is formed of a conductive material such as stainless steel. The leakage suppression member 4 of this embodiment is formed entirely of stainless steel. The leakage suppression member 4 has an inner flange portion 45, an outer flange portion 46, an abutment surface 41 that abuts against the insulating member 24, and an inner peripheral surface 44. The inner flange portion 45 protrudes toward the axis K side at the lower end of the leakage suppression member 4. The outer flange 46 protrudes from the lower end of the leakage suppression member 4 away from the axis K, i.e., in the radial direction. In this embodiment, the abutment surface 41 is the lower surface of the leakage suppression member 4. The abutment surface 41 is formed with an insulating portion 42 that is a recessed portion recessed toward the side away from the insulating member 24, i.e., toward the upper side. The insulating portion 42 is formed in a ring shape on the abutment surface 41 that surrounds the workpiece material 8, and the surface of the insulating portion 42 is conductive.

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

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

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 contacts 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, when the microwave frequency is 2.45 (GHz), it is preferable that 1/2 of the outer diameter D4 of the contact surface 41, i.e., the radius of the outer contour of the contact surface 41, is 30 (mm) or more and is a length that is spaced apart from the processing vessel 2. When the planar shape of the contact surface 41 is other than circular, it is preferable that the distance between the position closest to the workpiece material 8 on the outer periphery of the contact surface 41 and the center of the workpiece material 8 is 30 (mm) or more. Even if the center of the outer contour of the contact surface 41, which is circular in plan view, differs from the center of the workpiece material 8, it is preferable that the distance between the position on the periphery of the contact surface 41 closest to the workpiece material 8 and the center of the workpiece material 8 is 30 mm or more.

The inner peripheral surface 44 is the inner peripheral surface of the inner flange portion 45 of the leakage suppression member 4. The inner peripheral surface 44 abuts against the sheath expansion electrode 30. The leakage suppression member 4 has a through hole 43 that communicates between the insulating portion 42 and the space inside the processing vessel 2. The through hole 43 is formed in a circular shape in a plan view on the upper surface of the leakage suppression member 4. The through hole 43 extends upward from the upper end of the insulating portion 42.

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 have the same electrical potential, a 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 in accordance with instructions from the control unit 6. The negative electrode of the DC power supply 15 is electrically connected to the ground potential (GND). The positive voltage pulse generation unit 16 pulses the positive bias voltage supplied from the DC power supply 15. This pulsing process is a process in which the positive voltage pulse generation unit 16 controls the magnitude, period, and duty ratio of the positive bias voltage pulse in accordance with instructions from the control unit 6. The positive and negative bias voltages are, for example, bias voltages in the range of +300 to +390 (V). The voltage application unit 20 of the film forming apparatus 1 may not include a positive voltage pulse generation unit 16, and may apply a continuous positive bias voltage from a DC power source 15 to the sheath expansion electrode 30. The vacuum pump 3 is a pump that can evacuate the inside of the processing vessel 2 via a pressure adjustment valve 7.

The gas supply unit 5 supplies source gas for film formation into the processing vessel 2. For example, a mass flow controller (MFC) is used as the gas supply unit 5. The source gas includes, for example, a hydrocarbon gas such as _{CH4 or C2H2} and hydrogen gas ( _H2 ), and the inert gas includes, for example, nitrogen gas ( _N2 ). The gases are appropriately mixed and supplied into the processing vessel 2 under the control of the gas supply unit 5. Although not shown, an inert gas may also be supplied into the processing vessel 2.

The radiation thermometer 29 is disposed near the outside of the window 27 provided on the side wall of the processing vessel 2. The radiation thermometer 29 is electrically connected to the control unit 6. The radiation thermometer 29 receives infrared rays and calculates the intensity of the received infrared rays. The radiation thermometer 29 calculates the surface temperature of the workpiece 8 from the calculated infrared intensity, and outputs temperature information of the workpiece 8 to the control unit 6.

The control unit 6 controls the entire device. The control unit 6 includes a CPU, a ROM, and a RAM. The control unit 6 outputs a control signal 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 the control unit 6 confirms that the output temperature input from the radiation thermometer 29 is equal to or lower than a preset upper limit temperature, it outputs a control signal to the positive voltage pulse generation unit 16 and the microwave pulse control unit 11. If the temperature is equal to or higher than the upper limit temperature, the control unit 6 stops outputting the control signal and waits until the temperature falls below the upper limit temperature by natural cooling. The control unit 6 controls the application timing of the bias voltage pulse, the supply voltage, and the supply timing and supply power of the microwave pulse generated by the microwave oscillator 12. The control unit 6 outputs a flow control signal to the gas supply unit 5 to control the supply of the raw material gas and the inert gas. The processing vessel 2 has a vacuum gauge 26 that outputs a pressure signal indicating the pressure inside the processing vessel 2. The control unit 6 outputs control signals to the pressure adjustment valve 7 and the leak valve 33 based on the pressure signal input from the vacuum gauge 26 to control the pressure inside the processing vessel 2.

The microwave supply unit 9 supplies microwaves to the workpiece 8 from the introduction member 22 to generate plasma along the processing surface 10 of the workpiece 8. The microwave supply unit 9 includes 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 a pulsed 2.45 (GHz) microwave according to the instructions of the control unit 6 and supplies a microwave pulse to the isolator 17. The microwave pulse is supplied from the microwave oscillator 12 through the isolator 17, the tuner 18, the waveguide 19, the coaxial waveguide 21, and the introduction member 22 to the processing surface 10 of the workpiece 8. In this embodiment, the microwave oscillator 12 oscillates pulsed microwaves, but this is not limiting and it may also output continuous non-pulsed microwaves.

The isolator 17 prevents the reflected microwave from returning to the microwave oscillator 12. The tuner 18 matches the impedance before and after the tuner 18 so that the reflected microwave is minimized. The coaxial waveguide 21 protrudes upward from the waveguide 19 in a cylindrical shape 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.

The surface wave excited plasma generated when the MVP method is performed using the above-mentioned film forming apparatus 1 will be described. Normally, when generating surface wave excited plasma, microwaves are supplied along the interface between plasma at a certain level of electron (ion) density and a dielectric material in contact with the plasma. The supplied microwaves are propagated 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 by the high energy density surface wave and further amplified. This generates and maintains high density plasma. However, if this dielectric is replaced with a conductive workpiece material 8, the workpiece material 8 does not function as a waveguide for the surface wave, and favorable surface wave propagation and plasma excitation cannot be generated.

On the other hand, a layer of charged particles of essentially the same polarity, a so-called sheath layer, is formed near the surface of an object in contact with the plasma. When the object is a workpiece material 8 connected to a ground potential, the sheath layer is a layer with a low electron density, i.e., a layer of positive polarity and a relative dielectric constant ε ≒ 1 in the microwave frequency band. For this reason, a sheath expansion electrode 30 is provided around the lower end of the workpiece material 8, the workpiece material 8 is connected to a ground potential, and a positive bias voltage higher than the ground potential is applied to the sheath expansion electrode 30, so that the sheath thickness of the sheath layer formed along the processing surface 10 of the workpiece material 8 becomes thicker, that is, the sheath layer expands. This sheath layer acts as a dielectric that propagates surface waves to 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 a voltage set so that the potential difference with the ground potential is lower than the potential difference required to generate plasma.

Therefore, microwaves are supplied from the introduction member 22 arranged 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, and a positive bias voltage is applied to the sheath expansion electrode 30 arranged around the workpiece 8 and the introduction member 22, and the workpiece 8 is connected to ground potential, so that the microwaves propagate as surface waves along the interface between the sheath layer and the plasma. As a result, high-density excited plasma based on the surface waves is generated along the processing surface 10 of the workpiece 8. This high-density excited plasma is the above-mentioned surface wave excited plasma.

In the MVP method using the film-forming 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 a 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 to expand the sheath layer, generating 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 rapidly film-formed. The workpiece 8 is placed opposite the central conductor of the coaxial waveguide 21, so that the microwaves propagate efficiently upward.

A brief explanation of the film formation process using the MVP method will be given below. An operator or an automatic transport machine inserts the workpiece 8 into the recess 223 of the processing vessel 2, sets the workpiece 8 in the processing vessel 2, then connects the electrode 14 to the top end of the workpiece 8, connects the workpiece 8 to ground potential, and seals the processing vessel 2. The control unit 6 starts the vacuum pump 3, then sets the pressure adjustment valve 7 to full open, and evacuates the inside of the processing vessel 2 until a predetermined vacuum level is reached based on the pressure signal input from the vacuum gauge 26.

The control unit 6 controls the gas supply unit 5 and the pressure adjustment valve 7 to supply the inert gas and raw material gas to the processing vessel 2 until the pressure inside the processing vessel 2 reaches a predetermined value. Under the condition that the output temperature input from the radiation thermometer 29 is equal to or lower than the upper limit temperature, the control unit 6 controls the microwave oscillator 12 to generate a microwave pulse with a microwave power of 2.45 (GHz), and supplies the generated microwave pulse to the processing surface 10 of the workpiece material 8 via the isolator 17, the tuner 18, the waveguide 19, the coaxial waveguide 21, and the introduction member 22. The frequency of the microwave may be 0.3 to 50 (GHz), for example, 2.45 (GHz). The microwave may be a continuous microwave in addition to a pulsed microwave pulse.

The film forming apparatus 1 forms a film on the processing surface 10 of the workpiece 8 that protrudes into the processing vessel 2 beyond the upper end 31 of the sheath expansion electrode 30. When a hydrocarbon gas is used as the raw material gas, carbides of various structures such as graphite, diamond, and carbon nanotubes (CNTs) are generated by the plasma. The graphite and CNTs attached to the workpiece 8 are selectively etched by the hydrogen plasma, so that a diamond thin film is formed on the surface of the workpiece 8. Diamond is not conductive, and when a negative bias voltage is applied to the workpiece 8 as in the conventional technology, charges accumulate on the surface of the diamond. For this reason, the potential difference between the accumulated charges and the workpiece 8 causes abnormal discharge (arcing phenomenon), destroying the diamond film. The film forming apparatus 1 of this embodiment sets the potential of the workpiece 8 to the ground potential, thereby reducing the potential difference with the accumulated charges and suppressing the occurrence of the arcing phenomenon, thereby preventing the destruction of the diamond film and forming a high-quality diamond film.

The control unit 6 promptly exhausts the source gas and inert gas remaining in the processing vessel 2 using the vacuum pump 3, and then fully closes the pressure adjustment valve 7. The control unit 6 then opens the leak valve 33, and when the pressure inside the processing vessel 2 becomes the same as the outside air pressure, it notifies an alarm unit such as a liquid crystal display (LCD) that film formation is complete, and ends the film formation process. The operator or automatic conveyor removes the electrode 14 from the processed material 8, and takes out the processed material 8 with the film formed on the processing surface 10 from the processing vessel 2.

The evaluation test results will be described with reference to Figures 6 and 7. The workpiece 8 was a cutting tool made of superhard K10 with a diameter of 10 (mm), a total length of 85 (mm), and a groove length of 50 (mm). The film-forming device 1 without the leakage suppression member 4 was used as a comparative example, and the film-forming device 1 with the leakage suppression member 4 was used as an example. The area from the tip of the workpiece 8 to 50 (mm) was set as the processing surface 10. As shown in Figure 6, the microwaves oscillated by the microwave oscillator 12 of the film-forming device 1 were controlled to have a peak power of 500 to 1000 (W), a frequency of 1 (kHz), and a duty ratio 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 rates were _H2 at 200 (sccm) and _CH4 at 2 (sccm), and the pressure was controlled to 1 (kPa). Tests were performed under the same conditions for each of the comparative example and the example, and visual inspection was performed to check for the presence or absence of plasma generated due to microwave leakage near the insulating member 24. In Fig. 7, white circles indicate cases where plasma generation was not confirmed, and crosses indicate cases where plasma generation was confirmed.

As shown in FIG. 7, in the comparative example, plasma generation was confirmed under the conditions of a microwave peak power of 500 W and a bias voltage pulse peak voltage value of 370 V or 390 V, and a microwave peak power of 1000 W and a bias voltage pulse peak voltage value of 370 V. Plasma generation was not confirmed under other conditions in the comparative example. On the other hand, in the working example, 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.

8 to 10, a simulation result for confirming the effect of the structure of the leakage suppression member 4 on the effect of microwave leakage from the insulating member 24 will be described. The simulator used finite element analysis software COMSOL (registered trademark) Multiphysics 6.0, and used an RF module. The frequency of the microwave 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, the introduction member 22, and the insulating member 24 were set. The plasma used a permittivity and conductivity calculated with a pressure of 50 (Pa), a plasma density of 1E17 (1/m ³ ), and an electron temperature of 2 (eV). In the structure of the leakage suppression member 4, the first length D2 (mm) of the insulating portion 42, the width D1 (mm) of the insulating portion 42, and 1/2 (mm) of the outer diameter D4 of the abutting surface 41 were determined based on the simulation result under which plasma was not generated. The minimum electric field strength required to maintain plasma discharge is half the breakdown voltage, and a condition of 7500 (V/m) at 1.33 (kPa) was adopted 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). In other words, it is assumed that plasma will not be generated if 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 1/2 (mm) of the outer diameter D4 of the contact surface 41 were changed. The inner diameter of the insulating part 42 was 36 (mm), and the height D3 of the leakage suppression member 4 was 32.6 (mm). The thick lines in Figures 8 to 10 indicate the electric field strength threshold of 7500 (V/m).

In a simulation of the electric field strength (V/m) and the first length D2 (mm) of the insulating portion 42 shown in Fig. 8, the width D1 of the insulating portion 42 was set to 8 (mm), and 1/2 of the outer diameter D4 of the abutment surface 41 was set to 36 (mm). As shown in Fig. 8, when the first length D2 of the insulating portion 42 was 29.6 (mm), the electric field strength was 7124 (V/m), when it was 30.6 (mm), the electric field strength was 1944 (V/m), and when it was 31.6 (mm), the electric field strength was 3233 (V/m), and in all cases it was below 7500 (V/m). When the first length D2 of the insulating portion 42 is 28.6 (mm), the electric field strength is 12367 (V/m), and when the first length D2 of the insulating portion 42 is 32.6 (mm), the electric field strength is 8431 (V/m), both of which exceed 7500 (V/m). From the above, it is suggested that when the first length D2 (mm) of the insulating portion 42 is within the range of ±1 (mm) of the second length, the generation of plasma caused by microwaves leaking from the insulating member 24 can be suitably suppressed.

In the simulation of the electric field strength (V/m) and the width D1 (mm) of the insulating portion 42 shown in FIG. 9, the first length D2 of the insulating portion 42 was set to 30.6 (mm), and 1/2 of the outer diameter D4 of the abutting surface 41 was set to 36 (mm). As shown in FIG. 9, when the width D1 of the insulating portion 42 was 12 (mm) or less, the electric field strength was below 7500 (V/m), and when the width D1 of the insulating portion 42 was 1 (mm) or more, the width D1 of the insulating portion 42 and the electric field strength tended to increase monotonically. When the width D1 of the insulating portion 42 was 14 (mm), the electric field strength was 7543 (V/m), and when the width D1 of the insulating portion 42 was 16 (mm), it was 8697 (V/m). From the above, it was suggested that when the width D1 of the insulating portion 42 was 14 (mm) or less, the generation of plasma caused by microwaves leaking from the insulating member 24 can be suitably suppressed.

In the simulation of the electric field strength (V/m) and 1/2 (mm) of the outer diameter D4 of the contact surface 41 of the leakage suppression member 4 shown in FIG. 10, the first length D2 of the insulating portion 42 was set to 30.6 (mm), and the width D1 of the insulating portion 42 was set to 8 (mm). As shown in FIG. 10, when 1/2 of the outer diameter D4 of the contact surface 41 was 28 (mm) or more, a monotonically decreasing tendency was confirmed between 1/2 of the outer diameter D4 of the contact surface 41 and the electric field strength. When 1/2 of the outer diameter D4 of the contact surface 41 was 29 (mm) or less, the electric field strength exceeded 7500 (V/m), when 1/2 of the outer diameter D4 of the contact surface 41 was 29 (mm), the electric field strength was 8136 (V/m), and when 1/2 of the outer diameter D4 of the contact surface 41 was 30 (mm), the electric field strength was 7452 (V/m). From the above, it is suggested that if 1/2 of the outer diameter D4 of the contact surface 41 of the leakage suppression member 4 is 30 (mm) or more and is long enough to be placed away from the processing vessel 2, the generation of plasma caused by microwaves leaking from the insulating member 24 can be suitably suppressed.

The modified film forming apparatus 1 will be described with reference to Figures 11 and 12. In Figures 11 and 12, the same reference numerals are given to the same components as those of the film forming apparatus 1 of the above embodiment. The modified film forming apparatus 1 is different from the film forming apparatus 1 of the above embodiment in that it includes an introduction member 122, a sheath expansion electrode 130, and a leakage suppression member 54 instead of the introduction member 22, the sheath expansion electrode 30, and the leakage suppression member 4, and the other components are the same as those of the film forming apparatus 1 of the above embodiment. The introduction member 122, the sheath expansion electrode 130, and the leakage suppression member 54 will be described below. The introduction member 122 of the modified embodiment has a protruding portion 225 that protrudes into the processing vessel 2 and a base portion 222 that supports the protruding portion 225. The protruding portion 225 has a recessed portion 227 that is recessed downward from the introduction surface 226, which is the upper surface of the protruding portion 225. The recessed portion 228 is long in the microwave introduction direction J, that is, in the upward direction. 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 expansion electrode 130 is located below the introduction surface 226 of the introduction member 122. When the upper end 131 of the sheath expansion electrode 130 is located 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 expansion electrode 130 may be located at the same position as the introduction surface 226 of the introduction member 122 in the vertical direction.

The leakage suppression member 54 is disposed at a position electrically insulated from the workpiece material 8. The leakage suppression member 54 is cylindrical, extending in the vertical direction and having a cavity 47 in the center. The workpiece material 8 and the sheath expansion electrode 130 are disposed in the cavity 47. The leakage suppression member 54 has a contact surface 51 that contacts the insulating member 24 and an inner peripheral surface 44 similar to the above embodiment. At least the surface of the leakage suppression member 54 is formed of a conductive material such as stainless steel. The leakage suppression member 54 of this embodiment is entirely formed of stainless steel. The contact surface 51 of this embodiment is the lower surface of the leakage suppression member 54. The contact surface 51 is formed with insulating parts 52 and 53, which are recesses recessed on the side away from the insulating member 24, i.e., the upper side. The insulating parts 52 and 53 are formed in a ring shape surrounding the workpiece material 8 on the contact surface 41. The insulating parts 52 and 53 have different outer diameters. The width and first length of the insulating parts 52 and 53 are the same. The leakage suppression member 54 may have a through hole formed in each of the insulating parts 52 and 53 to communicate with the processing vessel 2.

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

The film forming apparatus 1 of the above embodiment includes a processing vessel 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 vessel 2. The processing vessel 2 contains a conductive workpiece 8. The introduction member 22 is provided around the processing vessel 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 disposed between the sheath expansion electrode 30 and the processing vessel 2, and electrically insulates the sheath expansion electrode 30 from the processing vessel 2. The leakage suppression member 4 is disposed at a position 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 to a side away from the insulating member 24. The film forming apparatus 1 can perform a film forming process using a known MVP method in which the microwave supply unit 9 supplies microwaves and the voltage application unit 20 applies a bias voltage to propagate the microwaves to the processing surface 10 of the workpiece 8, thereby generating high-density plasma near the workpiece 8. The film forming apparatus 1 can suppress the occurrence of the arcing phenomenon and form a high-quality film by setting the potential of the workpiece 8 to a ground potential using the electrode 14. Since the film forming apparatus 1 is provided with the leakage suppression member 4, it is possible to reduce the leakage of microwaves from the end face of the insulating member 24 into the processing vessel 2. Therefore, the film forming apparatus 1 can prevent microwave leakage from causing plasma discharge in unintended areas, or from damaging the insulating member 24, which can cause insulation between the sheath expansion electrode 30 and the processing vessel 2 to be lost. By applying a positive bias voltage to the sheath expansion electrode 30, the film forming apparatus 1 can increase the thickness of the sheath layer formed on the processing surface 10 of the workpiece 8, forming a uniform film on the processing surface 10.

The insulating portion 42 is formed in a ring shape surrounding the workpiece material 8 at the contact surface 41. The film forming apparatus 1 can reduce leakage of microwaves from the end face of the insulating member 24 into the processing vessel 2 in the circumferential direction around the workpiece material 8, compared to a case in which the insulating portion 42 is not formed in a ring shape surrounding the workpiece material 8.

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

Half of the outer diameter of the contact surface 41 of the leakage suppression member 4 is 30 (mm) or more, and the length is such that it is placed away from the processing vessel 2. The film forming device 1 can reduce the leakage of microwaves from the end face of the insulating member 24 into the processing vessel 2 compared to when half of the outer diameter of the contact surface 41 is less than 30 (mm) from the workpiece material 8.

The insulating portion 42 is a recess extending from the contact surface 41 away from the insulating member 24. The leakage suppression member 4 has a through hole 43 formed therein that connects the insulating portion 42 to the space inside the processing vessel 2. When performing the film formation process, the film formation device 1 suppresses unintended gases such as air from remaining in the insulating portion 42, thereby shortening the evacuation time inside the processing vessel 2.

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 forming apparatus 1 can suppress leakage of microwaves from the end face of the insulating member 24 into the processing vessel 2, compared to when the outer diameter D5 of the insulating member 24 is equal to or smaller than the outer diameter D4 of the contact surface 41 of the leakage suppression member 4.

The sheath expansion electrode 30 surrounds the periphery of the introduction surface 224 of the introduction member 22. Therefore, the microwaves introduced from the introduction surface 224 to the workpiece material 8 do not leak outside the sheath expansion electrode 30, and the film forming apparatus 1 can form a uniform, high-quality film over a wide area at high speed. No film is formed in the area where the sheath expansion electrode 30 surrounds the introduction member 22. Therefore, by setting the position of the upper end 31 of the sheath expansion electrode 30, the film forming apparatus 1 can reliably perform film formation on the processing surface 10. By setting the potential of the workpiece material 8 to ground potential, the film forming apparatus 1 can suppress the occurrence of the arcing phenomenon, which is a problem when forming a film with low conductivity. Therefore, the film forming apparatus 1 can form a film with high quality, uniformity over a wide area, and at high speed, even if it is a film with low conductivity such as diamond.

The contact surface 41 of the leakage suppression member 54 of the modified example has multiple insulating portions 52, 53 with different outer diameters. Compared to a case in which a single insulating portion 42 that surrounds the workpiece material 8 is formed on the contact surface 41, the film forming apparatus 1 can suppress leakage of microwaves from the end face of the insulating member 24 into the processing vessel 2.

The film forming apparatus of the present invention can be modified in various ways in addition to the above embodiment. The following modified examples may be appropriately combined within a range that does not cause any inconsistency. The workpiece material 8 does not need to be grounded. The leakage suppression member 4 may be made of ceramics with a conductive coating on its surface, as long as at least the surface is conductive. The planar shapes of the insulating member 24 and the leakage suppression member 4 do not need to be ring-shaped. The shapes, sizes, and arrangements of the introduction member 22, the sheath expansion electrodes 30, 130, and the leakage suppression members 4, 54 may each be appropriately changed. The contact surface 41 of the leakage suppression member 4 may contact the lower surface of the insulating member 24. The introduction direction J of the microwave does not need to be upward, and the arrangement of each member may be changed according to the introduction direction J of the microwave.

The shape and size of the insulating portion 42 of the leakage suppression member 4 may be appropriately changed in consideration of the configuration of the introduction member 22, the sheath expansion 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 from the contact surface 41 to the side away from the insulating member 24, or an insulating layer formed of an insulating material such as ceramics and extending from the contact surface 41 to the side away from the insulating member 24. The insulating portion 42 of the leakage suppression member 4 does not have to be formed in a ring shape surrounding the workpiece material 8 on the contact surface 41, and may be formed in any shape such as a circle, an arc, or a 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 a direction perpendicular to the contact surface 41 does not have to be within the range of ±1 (mm) of the second length. When a plurality of insulating parts are formed on the leakage suppression member, one insulating part does not have to be formed in a ring shape surrounding the workpiece material 8 on the contact surface of the leakage suppression member, and the other insulating parts may be formed in an arc shape or a line segment shape, and the first lengths of the insulating parts may be the same or different from each other. 1/2 of the outer diameter D4 of the contact surface 41 of the leakage suppression member 4 may be less than 30 (mm). The leakage suppression member 4 may not have a through hole 43 that communicates between the insulating part 42 and the space in the processing vessel 2. The arrangement, shape, and number of the through holes 43 may be changed as appropriate. When a plurality of insulating parts are formed to surround the workpiece material 8, the number of insulating parts may be changed as appropriate. The outer diameter D5 of the insulating member 24 may be equal to or smaller than the outer diameter D4 of the contact surface 41 of the leakage suppression member 4.

LIST OF SYMBOLS 1: Film forming apparatus 2: Processing vessel 4: Leakage suppression member 5: Gas supply unit 8: Material to be processed 9: Microwave supply unit 10: Processing surface 11: Microwave pulse control unit 12: Microwave oscillator 13: Microwave power source 14: Electrode 15: DC power source 17: Isolator 18: Tuner 19: Waveguide 20: Voltage application unit 21: Coaxial waveguide 22: Introduction member 24: Insulating member 30: Sheath expansion electrode 41: Contact surface 42: Insulating portion 43: Through hole 44: Inner peripheral surface 45: Inner flange portion 46: Outer flange portion 47: Cavity

Claims (7)

A processing vessel for accommodating a conductive workpiece;
a gas supply unit for supplying a gas to the processing vessel;
An introduction member that is provided around the workpiece and introduces microwaves;
a microwave supply unit that supplies the microwaves from the introduction member to the workpiece to generate plasma along a treatment surface of the workpiece;
a sheath expansion electrode disposed around the introduction member;
a voltage application unit that applies a positive bias voltage to the sheath expansion electrode to expand a 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 unit;
an insulating member disposed between the sheath expansion electrode and the processing vessel, electrically insulating the sheath expansion electrode from the processing vessel;
A film forming apparatus comprising: a leakage suppression member that is arranged in a position electrically insulated from the workpiece, and that has an abutment surface that abuts against the insulating member, and an insulating portion that extends from the abutment surface away from the insulating member. The film forming apparatus according to claim 1, characterized in that the insulating portion is formed in a ring shape on the contact surface so as to surround the workpiece material. The deposition apparatus according to claim 2, characterized in that the first length of the insulating part in the 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. The film forming apparatus according to claim 2 or 3, characterized in that 1/2 of the outer diameter of the contact surface of the leakage suppression member is 30 mm or more, and the length of the member is such that the member is disposed away from the processing vessel. the insulating portion is a recess extending from the contact surface toward a side away from the insulating member,
3. The film forming apparatus according to claim 1, wherein the leakage suppression member has a through hole formed therein, the through hole communicating the insulating portion with a space within the processing chamber. The film forming apparatus according to claim 2, characterized in that a plurality of insulating parts having different outer diameters are formed on the contact surface of the leakage suppression member. 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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