Manufacturing method and inspection method of interior member of plasma processing apparatus

Provided is a manufacturing method of an interior member of a plasma processing apparatus, which improves processing yield. The interior member is disposed inside a processing chamber of the plasma processing apparatus and includes, on a surface thereof, a film of a material having resistance to plasma. The manufacturing method includes: a step of moving a gun by a predetermined distance along the surface of the interior member to spray the material to form the film, and disposing a test piece having a surface having a shape simulating a surface shape of the interior member within a range of the distance within which the gun is moved and forming the film of the material on the surface of the test piece; and a step of adjusting, based on a result of detecting a crystal size of the film on the surface of the test piece and presence or absence of a residual stress or inclusion of a contaminant element, a condition of forming the film on the surface of the interior member by the gun.

TECHNICAL FIELD

The present invention relates to a manufacturing method and an inspection method of an interior member, which forms an interior of a processing chamber of a plasma processing apparatus for forming plasma in the processing chamber inside a vacuum container and processing a sample, such as a semiconductor wafer to be processed, which is disposed in the processing chamber, and the present invention relates to a manufacturing method and an inspection method of an interior member in which a film having plasma resistance is formed on a surface of the interior member forming an inner wall of the processing chamber.

BACKGROUND ART

Plasma etching is applied to microfabrication in manufacture of an electronic device and a magnetic memory. Processing accuracy required for the plasma etching is increasing year by year as devices are highly integrated. In order to improve yield of a plasma etching apparatus, it is necessary to reduce generation of foreign particles.

Since a processing chamber of a plasma processing apparatus used for the plasma etching is disposed inside a vacuum container, the processing chamber is made of metal such as aluminum or stainless steel. Since an inner wall surface of the processing chamber is exposed to plasma, a protective film having plasma resistance is formed on the surface. As such a protective film, a film made of yttrium oxide is generally used.

It is known in the related art that such a film containing yttrium oxide as a material is generally formed by using plasma spraying, SPS spraying, explosion spraying, low-pressure spraying, or the like. For example, in an atmospheric plasma spraying method, a technique is provided in which raw material powder with a size of 10 μm to 60 μm is introduced into a plasma flame together with a transport gas, and raw material particles in a molten or semi-molten state are jetted onto a surface of a base material to be adhered thereto to form a film. On the other hand, in the plasma spraying method, there are problems that surface irregularities are large, or many pores are formed inside the film, and particles that have entered these pores cause a reaction with the film and other members, which causes film consumption and corrosion.

Solutions to such problems have been studied in the related art. For example, when a film made of yttrium oxide is exposed to plasma of a fluorine-based gas, the film reacts with fluorine and the like in the plasma and vaporizes, so that the film is consumed. Therefore, a technique of forming a film by atmospheric plasma spraying using yttrium fluoride as a material is known in the related art. As such a technique, for example, one disclosed in JP-A-2013-140950 (PTL 1) is known in the related art.

On the other hand, when a pressure in the processing chamber is increased or decreased or a sample such as a semiconductor wafer is processed by forming plasma, a member disposed inside the processing chamber of the plasma processing apparatus faces the plasma and is repeatedly subjected to interaction such as heat, collision and adhesion of particles, or the like. It is required for interior members inside the processing chamber to keep the life of the interior members long by reducing damage and deterioration of the film as much as possible even under such an environment where conditions change. Therefore, in a process of manufacturing the interior members, it is necessary to inspect with higher accuracy whether a shape and performance are within a permissible range of an intended specification after the film is formed.

For example, because of the above problems, a surface of a member forming the inner wall inside the processing chamber of the plasma processing apparatus is protected by forming a film having excellent plasma resistance. However, as the required processing accuracy increases, a size of foreign particles generated inside the processing chamber also decreases, and it is required to reduce the generation thereof. Accordingly, in the related art, the film on the surface of the member forming the inner wall of the processing chamber is evaluated by detecting values of porosity, surface roughness (Ra), a crystallite size, a phase ratio, and the like of the film after the film is formed or after a post-treatment, and comparing the values with a permissible range of a predetermined specification. JP-A-2017-190475 (PTL 2) is known as an example of such a technique.

Further, when a film is formed by spraying on a plurality of surfaces of a certain type of member, in order to form a film having the same performance and characteristic such as a shape as possible by any one member and other members, a method has been known in the related art in which a part of a member is cut out and used for inspection, or one of a plurality of manufactured products is used for inspection. As an example of such a technique, one disclosed in JP-A-8-20858 (PTL 3) and JP-A-9-61318 (PTL 4) has been known.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

However, the above-described techniques in the related art have a problem because the following points are not sufficiently taken into consideration.

That is, in a case where a film having plasma resistance or heat resistance is formed on the surface of the member that is disposed inside the processing chamber of the plasma processing apparatus and forms the inner wall thereof, generally, after conditions such as an operation of an apparatus for forming a film and a film forming rate are set, a film is formed and a post-treatment is further performed. However, in a technique in the related art, after the film on the surface of the internal member is formed, the film is not evaluated by comparing the characteristics such as the porosity, the surface roughness (Ra refers to arithmetic mean roughness), the crystallite size, and the phase ratio of the film with the predetermined permissible range, and, for example, the inspection of the member is limited to visual inspection. On the other hand, since the inner wall of the processing chamber has irregularities, openings, and end portions, it is not clear whether the film formed on the surface of the member forming the inner wall has desired characteristics and performance (such as the porosity, the surface roughness, a residual stress, the crystallite size, and the phase ratio) at portions where respective members are disposed.

As in PTL 3, in a case where a part of the member inside the processing chamber is cut out and the above inspection is performed, it is necessary to, for example, wash the part after the part of the member to be inspected is cut from the member. Therefore, the film of the part to be inspected may not be formed in the same process as that of other members of the same type, and in a cutting step, foreign particles may be generated on a surface of the film to be inspected, and the accuracy of the inspection may be impaired.

Further, as in PTL 4, for a plurality of members of one type that form the inner wall of the processing chamber, a film is formed under the same predetermined conditions and specifications, and one of the members is used for inspection. A dimension of the member increases, and especially in a case of a structure in which one member forms a main part of an entire inner wall portion of the processing chamber, such as plasma processing apparatuses in recent years, a unit price of the member may be large and manufacturing cost of the plasma processing apparatus may be significantly increased due to the inspection. As described above, in the techniques of the related art, in the plasma processing apparatus, the performance of the film of the member that is disposed inside the processing chamber and forms the inner wall, that is the performance of the plasma processing apparatus greatly varies, and reliability of the plasma processing apparatus and processing yield are impaired. Further, no consideration is given to the problem that the manufacturing cost is increased.

An object of the invention is to provide a manufacturing method and an inspection method of an interior member of a plasma processing apparatus which has improved processing yield and reliability.

Solution to Problem

The above object is achieved by providing a manufacturing method of an interior member which is arranged inside a processing chamber disposed inside a vacuum container of a plasma processing apparatus configured to process a wafer by using plasma formed in the processing chamber, and which includes, on a surface of the interior member, a first film of a material having resistance to the plasma. The manufacturing method includes: a step of forming the first film by spraying the material onto the surface of the interior member by moving a gun by a predetermined distance along the surface of the interior member, and forming a second film by spraying the material on a surface of a test piece which has a shape simulating a surface shape of the interior member and which is disposed within a range of the predetermined distance, by moving the gun within the predetermined distance; and a step of adjusting a condition of forming the first film on the surface of the interior member by the gun, based on a result of detecting at least one of a crystal size of the second film on the surface of the test piece, a residual stress, and a contaminant element.

More specifically, in parallel with a step of forming a film on an inner wall surface around a central axis of a cylindrical or ring-shaped ground electrode, which is disposed inside the vacuum container in the plasma processing apparatus and forms the inner wall surface of the processing chamber where plasma is formed in an inner space, by moving a film-forming gun along a direction along the central axis and a predetermined path around the axis, a film is also formed on a test piece on a surface of one or more test pieces disposed on the path for movement of the gun, such as an upper end or an end portion of a lower end of the ground electrode, an opening of the ground electrode, and the like. Further, the quality of the ground electrode is determined based on a result of inspecting a predetermined item of the film on the surface of the test piece. A shape of the test piece has (1) the same shape as an end portion of the opening, and has a film boundary portion with a film on a first surface but no film on a second surface, has (2) the same shape as an inclined surface where a spray direction of the film-forming gun is not perpendicular to the surface of the ground electrode, and has (3) an end portion on which a film is formed on an inner peripheral surface-an end tip portion-an outer peripheral surface as an end portion of the ground electrode. (4) One of the test pieces has the above-described shapes (1) to (3).

Advantageous Effect

According to the invention, a manufacturing method and an inspection method of an interior member of a plasma processing apparatus, which has improved processing yield and reliability, are provided.

DESCRIPTION OF EMBODIMENTS

Embodiments of the invention will be described with reference toFIGS.1to16.

FIG.1is a longitudinal cross-sectional view schematically showing an outline of a configuration of a plasma processing apparatus according to an embodiment of the invention. The plasma processing apparatus shown in this figure is a plasma etching apparatus that forms plasma in a processing chamber inside a vacuum container, and performs etching processing by using the plasma on a film structure, which has a mask layer previously formed on a surface of a sample such as a semiconductor wafer placed in the processing chamber and a film layer to be processed below the mask layer.

A plasma processing apparatus100of the embodiment shown inFIG.1roughly includes: a metal vacuum container1a part of which has a cylindrical shape; a plasma forming unit which is disposed above the vacuum container1, includes a generator that generates an electric field or a magnetic field for forming plasma in a depressurized space inside the vacuum container1, and supplies the generated electric field or magnetic field to the internal space; and an exhaust unit which includes a vacuum pump that is disposed under the vacuum container1and is connected to the vacuum container1to exhaust the space inside the vacuum container1to reduce a pressure. Further, the vacuum container1is connected to a transfer container whose outer side wall is another vacuum container1and in which a wafer, which is a sample to be processed, is transferred in a depressurized internal transfer space. A side wall of the vacuum container1is provided with a gate, which is a passage that penetrates the side wall in a horizontal direction and connects the inside and the outside of the vacuum container1, and through which the wafer is transferred to the inside. The transfer container is connected to a position of the side wall of the vacuum container1surrounding an outer periphery of an opening on an outer side of the gate, and the space inside the vacuum container1and the space inside the transfer container can communicate with each other.

The vacuum container1includes a processing chamber7which has a space in which the sample to be processed is disposed and plasma is formed. The processing chamber7is provided with a discharge unit which is disposed on an upper part, has a cylindrical shape, and in which plasma15is formed, and a stage6which is a sample stage having a cylindrical shape and is disposed in a lower space connected to the discharge unit. The stage6has a circular upper surface which is a surface on which a wafer4that is a substrate to be processed is placed. Inside the stage6, a heater for heating the wafer4and a cooling medium passage through which a cooled cooling medium flows are disposed. A pipe for supplying a helium (He) gas, which is a heat transfer gas, is provided between the circular upper surface of the stage6and a back surface of the wafer4placed on the upper surface.

Further, a metal electrode is disposed inside the stage6, and a high frequency power supply14, which supplies, to the electrode, a high frequency power for forming a potential on the wafer4during processing of the wafer4using the plasma15, is electrically connected to the electrode via an impedance matching device13. Charged particles such as ions inside the wafer4are attracted to a surface of the wafer4due to a potential difference between plasma and a bias potential formed on the wafer4by the high frequency power during the formation of the plasma15, and etching processing is facilitated. In the present embodiment, a metal base material having a cylindrical or disk shape is disposed inside the stage6, the base material is connected to the high frequency power source4, the heater and the cooling medium passage are disposed inside the base material, and the pipe for supplying the He gas is disposed so as to penetrate the base material.

The wafer4is placed on a tip end portion of an arm of a transfer apparatus (not shown) such as a robot arm disposed in the transfer space inside the transfer container, and is transferred to the processing chamber7, and then placed on the stage6. An electrode (not shown) for electrostatically adsorbing the wafer4by being supplied with a direct current power is disposed inside a dielectric film, which is disposed so as to form a placing surface of the wafer4of the stage6and to cover an upper surface of the base material. The wafer4placed on the stage6is adsorbed and held on the upper surface of the dielectric film due to an electrostatic force generated by applying a direct current voltage to the electrode for electrostatic adsorption. Further, in this state, the He gas is supplied to a gap between the back surface of the wafer4and the upper surface of the dielectric film, which is the placing surface of the stage6, through the pipe inside the base material, and heat transfer between the wafer4and the cooling medium flowing in the cooling medium passage inside the base material is facilitated, so that a temperature of the wafer4is adjusted.

Above an upper end portion of the cylindrical side wall member surrounding the discharge unit of the vacuum container1, a shower plate2and a window member3each having a disk shape are placed with a ring-shaped member interposed therebetween. The window member3and a side wall member41on an outer periphery of the discharge unit form the vacuum container1. Seal members such as O-rings are interposed between a lower surface of an outer peripheral edge portion and the ring-shaped member, that is disposed between the lower surface and an upper surface of the upper end portion of the side wall member, and between the ring-shaped member and the lower surface, and these members are connected. The processing chamber7inside the vacuum container1and the outside atmosphere at an atmospheric pressure are airtightly partitioned.

As will be described later, the window member3is a disk-shaped member made of ceramics (quartz in the present embodiment) through which an electric field of microwaves for forming the plasma15is transmitted. The shower plate2having a plurality of through holes9in a central portion thereof is disposed below the window member3with a gap8having a predetermined size. The shower plate2faces the inside of the processing chamber7to form a ceiling surface thereof, and a processing gas, whose flow rate is adjusted to a predetermined value by a gas flow rate control unit (not shown), is introduced into the gap8. The processing gas diffuses in the gap8and then is introduced into the processing chamber7through the through holes from above. The processing gas is introduced into the gap8by opening a valve51disposed on a processing gas supply pipe50connected to the ring-shaped member.

Further, a bottom of the vacuum container1has a passage, which connects the inside and the outside of the processing chamber7, and through which the plasma15inside the processing chamber7, products generated during the processing of the wafer4, and particles of the processing gas are discharged. A circular opening of the passage on an inner side of the processing chamber7is disposed, as an exhaust port, at a position immediately below the stage6, which is disposed above, such that central axes can be regarded as the same when viewed from above. A turbo molecular pump12forming the vacuum pump of the exhaust unit and a dry pump11disposed downstream of the turbo molecular pump12are connected to a bottom surface of the vacuum container1. Further, an inlet of the turbo molecular pump12is connected to the exhaust port by an exhaust pipe.

A valve18is disposed on the exhaust pipe for connecting the turbo molecular pump12and the dry pump11. Another exhaust pipe10, which is connected to the bottom surface of the vacuum container1and is connected to the bottom of the processing chamber7, is connected to a portion of the exhaust pipe between the valve18and the dry pump11. The exhaust pipe10is connected so as to be branched into two pipes on the way and then merge again into one pipe, and valves17,19are disposed on the branched portions, respectively. The valve17in the valves17,19is a slow exhaust valve for slowly exhausting the processing chamber7from the atmospheric pressure to the vacuum by the dry pump11, and the valve19is a main exhaust valve for exhausting by the dry pump11at a high speed.

The processing chamber7is provided with a pressure sensor75for detecting a pressure inside the processing chamber7. In a space at a lower portion of the processing chamber7, between a bottom surface of the stage6and the processing chamber7, and above the exhaust port of the present embodiment, a disk-shaped pressure adjusting plate16is disposed which moves in the up-down direction in the space to open and close the exhaust port and increase or decrease an opening area of the exhaust port so as to adjust a flow rate or a speed of an exhaust gas. The pressure in the processing chamber7is increased or decreased depending on balance in flow rate or speed of the processing gas or another gas introduced into the processing chamber7through gas introduction ports, which are the through holes of the shower plate2, and the exhaust gas from the exhaust port. For example, the gas is introduced into the processing chamber7from the shower plate2at a flow rate or a speed set to a predetermined value corresponding to processing conditions of the wafer4, and the flow rate or the speed of the exhaust gas is adjusted to realize the pressure in the processing chamber7corresponding to the processing conditions by adjusting a position of the pressure adjusting plate16in the up-down direction.

The plasma forming unit is disposed above a metal side wall surrounding the outer periphery of the discharge unit of the processing chamber7on an upper portion of the vacuum container1and the window member3at a portion of an outer peripheral side of the window member3. The plasma forming unit has a magnetron oscillator20that outputs the electric field of the microwaves for forming the plasma15, and a waveguide21for propagating the microwaves to the processing chamber7. The waveguide21has a square portion, which extends in the horizontal direction (left-right direction in the figure) and has a rectangular or square cross section, and a circular portion having a cylindrical shape, which is connected to one end portion of the square portion and extends in the up-down direction. The magnetron oscillator20is disposed at the other end portion of the square portion.

A lower end of the circular portion is connected to an upper end of a cylindrical hollow portion, which is disposed above the window member3and has a diameter approximately similar to that of the window member3and larger than a diameter of the circular portion. Further, a ring-shaped solenoid coil22and solenoid coil23, which are units to be supplied with direct current power to generate a magnetic field, are provided above the hollow portion and at a position surrounding the discharge unit of the processing chamber7on an outer peripheral side of the side wall of the vacuum container1surrounding an outer peripheral side of the hollow portion and the discharge unit.

An inner side wall surface of the side wall member41of the processing chamber7is a surface exposed to the plasma15formed in the discharge unit, but an interior member is required that functions as a ground in the processing chamber7in order to stabilize the potential of the plasma15. In the present embodiment, a ring-shaped ground electrode40that functions as a ground in the discharge unit is disposed above the stage6so as to surround the upper surface of the stage6. The ground electrode40is made of a metal member, such as a stainless alloy or an aluminum alloy, as a base material. Since the ground electrode40is exposed to the plasma15, the ground electrode40interacts with highly reactive and corrosive particles in the plasma15. Therefore, there is a high possibility that a generated product will be a source of corrosion, metal contamination, and generation of foreign particles.

Therefore, in order to reduce such a problem, as shown schematically in a cross-sectional view enlarged in a lower left part ofFIG.1, an inner wall material film42made of a material having high plasma resistance is disposed on a surface of the ground electrode40of the present embodiment so as to cover the surface. By covering the surface using the inner wall material film42, the ground electrode40can reduce damage such as corrosion to the ground electrode40caused by the plasma while maintaining the function as ground. The film42may be a laminated film.

On the other hand, although the side wall member41surrounding the discharge unit of the vacuum container1of the present embodiment is made of a metal base material such as a stainless alloy or an aluminum alloy, the side wall member41does not function as a ground. In order to reduce the generation of the corrosion, the metal contamination, and the foreign particles caused by the side wall member41being exposed to the plasma15, an inner surface of the side wall member41is subjected to a surface treatment such as a passivation treatment, thermal spraying, PVD, and CVD. Further, in order to prevent a base material of the side wall member41from being directly exposed to the plasma15, a ring-shaped or cylindrical-shaped interior member made of ceramics such as yttrium oxide or quartz may be disposed between an inner side wall surface of the side wall member41having a cylindrical shape and the discharge unit of the processing chamber7and along the inner side wall surface so as to cover the inner side wall surface with respect to the plasma15. The interior member between the side wall member41and the plasma15prevents contact between the side wall member41and the plasma15and reduces consumption of the surface-treated side wall member41caused by the plasma15.

When the wafer4, which is placed on the tip end portion of the arm of the robot arm and is transferred from the transfer space (transfer chamber) inside the transfer container into the processing chamber7through a gate49on the side wall of the vacuum container1, is placed on a placing surface of the stage6, and the robot arm moves out of the processing chamber7, an opening of the gate49is airtightly closed by a gate valve50disposed on an outer side of the vacuum container1to seal the inside of the processing chamber7. When the wafer4is electrostatically adsorbed and held on the placing surface of the stage6, the processing gas is introduced from the shower plate2, an amount of the exhaust gas from the exhaust port is adjusted by an operation of the pressure adjusting plate16, and the pressure in the processing chamber7is set to a predetermined pressure suitable for processing.

The electric field of the microwaves oscillated from the magnetron oscillator20propagates through the waveguide21and is radiated into the processing chamber7through the quartz window member3and the quartz shower plate2below the window member3. Electron cyclotron resonance (ECR) is formed by the interaction between the electric field of microwaves and the magnetic field generated by the solenoid coils22,23, atoms or molecules of the processing gas introduced into the processing chamber7from the gas introduction ports of the shower plate2are excited, ionized, and dissociated, and the plasma15is generated in the discharge unit.

When the plasma15is formed, the high frequency power is supplied from the high frequency power supply14to the base material of the stage6, the bias potential due to the high frequency power is formed on the wafer4, and the etching processing of the film layer to be processed is started according to a processing pattern of the mask layer having the film structure formed on the wafer4. When an end point of the etching processing or reaching of a predetermined remaining film thickness is detected by an end point detector (not shown) for processing, the supply of the high frequency power, the microwave electric field, and the magnetic field are stopped, the plasma is extinguished, and the etching processing is completed. Further, after the supply of the processing gas is stopped, exhaust (high vacuum exhaust) processing is performed until the inside of the processing chamber7reaches a high degree of vacuum.

FIG.2is a perspective view schematically showing an outline of a configuration of an interior member forming the ground electrode shown inFIG.1.FIG.2shows a diagram of the ground electrode40having the ring shape or the cylindrical shape shown inFIG.1as viewed obliquely from below to above.

As shown in the figure, the ground electrode40is provided with the cylindrical shape having a predetermined thickness as a whole, and has an inner side wall and an outer side wall each having an inner diameter of the same value around a central axis in the up-down direction. Further, the ground electrode40has a cylindrical main side wall portion and a ring-shaped electrode portion disposed further above an upper end of the main side wall portion, and an outer peripheral wall surface of the electrode portion at a radial position from the central axis in the up-down direction is smaller than that of the lower main side wall portion. A rectangular opening43of a through hole forming the gate49is disposed in a middle portion in the up-down direction of the cylindrical main side wall portion.

In a state where the ground electrode40is mounted inside the processing chamber7, the ground electrode40is disposed between the inner side wall and the processing chamber7, and the ground electrode40has a length in the up-down direction enough to cover the inner side wall surface of the side wall member41of the vacuum container1with respect to the plasma15such that a lower portion of the ground electrode40is disposed on the outer peripheral side of the stage6and on an inner side of the side wall member41surrounding the stage6, and an upper portion of the ground electrode40is disposed on the inner side of the side wall member41surrounding the discharge unit. This shape protects the side wall member41from the interaction of the plasma15.

Further, the side wall member41having the cylindrical shape of the vacuum container1matches a shape in which an inner diameter of the upper portion is smaller than that of the lower portion in an up-down axial direction. An outer diameter of the electrode portion, which forms the upper portion of the ground electrode40and covers an inner surface of the inner side wall of the upper portion of the side wall member41surrounding the discharge unit with respect to the plasma15is disposed closer to a center side than an outer shape of the lower main side wall portion, in other words, a small diameter portion is formed. Further, as described later, the ground electrode40has a step portion between the upper electrode portion and the lower main side wall portion, and a surface of the inner side wall has a shape recessed toward the outer peripheral side as the surface goes downward from above along the central axis. From this point, it can be said that the ground electrode40has a large diameter portion at a lower portion thereof.

A shape of a part of the ground electrode40shown inFIG.2and a configuration of a test piece having a similar shape corresponding to the part will be described with reference toFIGS.3A to4B.FIGS.3A,3B,4A, and4Bare cross-sectional views schematically showing parts of the ring-shaped ground electrode shown inFIG.2and shapes of longitudinal cross sections along the central axis in the up-down direction of test pieces having surface shapes similar to the parts. Each of theFIGS.3A and4Ais a diagram showing a cross-sectional shape of the part of the ground electrode40, and theFIGS.3B and4Bare diagrams showing cross-sectional shapes of test pieces52a,52beach having a surface shape similar to the shape of the part of the ground electrode40shown inFIGS.3A and4A.

As described above, the ground electrode40of the present embodiment has the base material made of an aluminum alloy and the film42having the plasma resistance on the surface thereof. Further, in a state where the ground electrode40is disposed inside the processing chamber7, the inner side wall surface and the upper end portion of the ring-shaped electrode portion on the upper portion of the ground electrode40are portions facing the plasma15when the plasma15is formed in the discharge unit. Since the plasma15may enter a gap between the electrode portion and the side wall member41and wrap around an outer side wall surface of the electrode portion, the film42is also disposed at a portion extending from the upper end portion of the electrode portion to the outer side wall surface so as to cover the portion. On the other hand, in a state where the ground electrode40is mounted inside the processing chamber7, since a lower end portion of the ground electrode40is located below the upper surface of the stage6and disposed apart from the plasma15, the film42is not disposed on the outer side wall surface.

Next, the test piece used in a step of manufacturing the ground electrode40of the present embodiment will be described. The test piece of the present embodiment has a mounting surface that comes into contact with a jig when the test piece is mounted on the jig, and a film target surface48that is an inspection surface on an opposite side to the mounting surface and on which a film used for inspection is formed. An inspection surface48has a shape similar to a shape of a part of an inner wall surface of the ring-shaped ground electrode40shown inFIG.2. In particular, a flat surface forming a part of the inspection surface48and a curved surface connected to the flat surface have a cross-sectional shape similar to a shape of a cross section along a rotation axis of the ground electrode40. In a manufacturing method according to the present embodiment, such a test piece is disposed adjacent to the ground electrode40during a step of forming the film42on the surface of the ground electrode40, and in parallel with the formation of the film42on the surface of the base material of the ground electrode40, the test film42is formed on the inspection surface48of the test piece under the same conditions as the case of the forming of the film42.

A test piece52of the present embodiment includes a plurality of plane portions corresponding to a part of shapes of cylindrical and conical side walls having a central axis in the up-down direction on the inner wall surface of the ground electrode40, and at least one curved surface connected between two upper and lower plane portions among these planes. That is, the test piece52ahas a shape similar to a shape of an inner wall surface of a portion including the upper electrode portion and the opening43of the ground electrode40shown inFIG.3A, as the inspection surface48on a surface of the test piece52ashown inFIG.3Bon a left side in the figure.

Above the opening43of the electrode portion of the ground electrode40shown inFIG.3A, a portion where the surface has a cylindrical shape at the same radial position from the central axis is a portion whose longitudinal cross section is a straight line in the up-down direction. The test piece52ahas a shape similar to these portions on a side wall surface, which is a film target surface, on the left side in the figure, and has two flat surfaces71,72, which are connected to each other and have a width of 20 mm in the up-down direction, on the upper portion.

Further, a portion below the opening43shown inFIG.3Aof the ground electrode40is a portion having a shape of the cylindrical side wall surface whose surface is at the same radial position from the central axis, and of a conical side wall which is on a lower side of the above portion, and whose radius decreases toward the central axis side of the cylinder as going downward. That is, the ground electrode40has a shape that extends as a straight line by changing a direction from a linear portion in the up-down direction to a center side (left side in the figure) as a line showing the inner wall surface of the longitudinal cross section goes downward. The test piece52ashown inFIG.3Bhas, as a portion of the inspection surface48corresponding to the shape of the lower portion of the ground electrode40shown inFIG.3A, two flat surfaces73,74, which are on an upper side and a lower side respectively and each of which has a width of 20 mm in the up-down direction. The lower flat surface74forms an inclined surface so as to project toward a front side (left side in the figure) as the flat surface74goes downward when viewed from the left side in the figure.

In the test piece52aof the example, since a portion of a mounting surface on an opposite side (right side in the figure) of the inclined surface74is a vertical surface that is not inclined in the up-down direction in the figure, a lower portion of the test piece52aincluding the surface74has a taper shape in which a thickness of the member in a left-right direction in the figure monotonically increases as going downward. A curved surface75, that is, a curved surface having a central axis in a horizontal direction (a direction perpendicular to the figure in the figure) and having the same shape as a part of the cylindrical side wall having a predetermined radius R in the up-down direction, is disposed between the surfaces73,74. The curved surface75has a radius of curvature of 200 mm, and forms the inspection surface48. Upper and lower end portions of the curved surface75smoothly connect a lower end portion of the surface73and an upper end portion of the surface74.

The opening43of the ground electrode40is difficult to handle when the test piece has a through hole. Therefore, the test piece52ahas, at a middle section in the up-down direction, a recessed portion76whose depth is the same as a thickness of the main side wall portion of the ground electrode40in the opening43and whose opening shape is the same rectangular shape as the opening43. An inner surface of the recessed portion76excluding an edge portion of the opening of the recessed portion76does not form the inspection surface48, and the film42is not formed thereon, but the edge portion of the opening is chamfered so as to be a surface inclined with respect to a surrounding surface, or has a curved shape and forms the inspection surface48.

As will be described later, the film42is disposed on the inspection surfaces71to75of the test piece52asuch that the same material as the film42is used to form the same thickness under the same conditions. As will be described later, the formation of the film42on the inspection surface48is performed by disposing the ground electrode40and the test piece52aadjacent to each other and using a device for forming the same film in parallel on the inner wall surface of the ground electrode40and the inspection surface of the test piece52ain the step of forming the film42on the surface of the ground electrode40.

At an upper end portion of the test piece52a, as a portion corresponding to the inner side wall surface and the outer side wall surface of the electrode portion of the ground electrode40, an upper end surface and the lower inspection surface48connected to the upper end surface and both surfaces on the mounting surface side (these surfaces) form the inspection surface48. The inspection surface is disposed on the outer side wall surface from a tip end of the upper end portion to a position of 10 mm on the lower flat surface, and the film42is formed.

FIG.4Ashows a shape of an inner wall surface of a portion below the part of the ground electrode40shown inFIG.3A. Similarly toFIG.3A, the portion shown in this figure also has a plurality of portions, whose surface has a shape of a cylindrical side wall surface, in the up-down direction, but a radius of the cylindrical side wall surface of the lower portion is larger than that of the upper portion. It is different fromFIG.3Ain that a portion whose surface has a shape of a truncated cone-shaped side wall surface is provided between these upper and lower portions, and a so-called radial step between the three portions, which is connected via a curved surface, is provided.

The inspection surface48, which forms a side wall surface on a left side of the figure of the test piece52bhaving a shape similar to the shape of the inner wall surface of the ground electrode40, has flat surfaces81,83, which are spaced vertically and respectively have a width (length) of 20 mm in the up-down direction, and a flat surface82, which is disposed between these surfaces81,83and approaches the inspection surface side forming a side wall surface on a right side of the figure as the flat surface82goes downward. Upper and lower curved surfaces84,85, which have central axes in the horizontal direction (the direction perpendicular to the figure in the figure) and have the same shape as a part of the cylindrical side wall having the predetermined radius (radius of curvature) R, are disposed between the flat surfaces81,82, and between the flat surfaces82,83, and form the inspection surface48. Adjacent and parallel end portions of the flat surfaces81,82,83are smoothly connected.

The shape of each of the curved surfaces75,84,85corresponds to a part of the cylindrical side wall, and each of these faces has the fixed radius of curvature and the central axis. Further, the curved surfaces75,84,85and the adjacent flat surfaces73,74or81,82,83are configured such that the upper edge and the lower edge that are in contact with each other are connected without any step, and tangents thereof match each other. When an angle at which planes including the upper and lower flat surfaces73,74and the flat surfaces81,82,83, which are adjacent to each other with the curved surfaces75,84,85interposed therebetween, intersect is 5 degrees or less, a distance from the intersection to the upper and lower edges of the curved surface is 17.5 mm or less.

The shapes of the test pieces according to the embodiment shown inFIGS.3A to4Bwill be described in more detail with reference toFIGS.5and6.FIG.5is a perspective view schematically showing outlines of shapes of test pieces formed by dividing the test piece according to the embodiment shown inFIG.3B.FIG.6is a perspective view schematically showing outlines of shapes of test pieces formed by dividing the test piece according to the embodiment shown inFIG.4B.

As shown in these figures, the test pieces52a,52bare further respectively divided into three and two in the up-down direction. The test piece52ais vertically divided by a plane that passes between the surfaces71,72in the horizontal direction on the upper portion, and is further vertically divided by a plane as a cross section in the horizontal direction that passes through the inside of the recessed portion76between the surfaces72,73. A tip end portion shape test piece53, a recessed inclined shape test piece55, and an opening shape test piece56are formed respectively. Further, the test piece52bis vertically divided between the surfaces82,85, and is divided into a projection inclined shape test piece54and the recessed inclined shape test piece55. Each of the test pieces53to56has a length within 40 mm and a width within 20 mm.

A size of such a test piece can be changed according to a sample size required according to specifications of an inspection apparatus that inspects the film42, but at a circumference of 2.5 mm, the test piece is likely to be affected by external force when the test piece is removed. Therefore, depending on conditions, it is better not to set the circumference as an analysis area. Therefore, it is desirable that the size of the test piece is 5 mm larger or more than a measurement size.

In the present embodiment, the same material as the ground electrode40is used for the test pieces53to56having the shapes shown inFIGS.5and6, but a length (width) in the up-down direction of at least one of the flat surfaces81,82forming the inspection surface48of the projection inclined shape test piece54may be shortened by about 5 mm. Further, in the present embodiment, the test pieces52a,52bare vertically divided into a plurality of parts, but the test piece52aor the test piece52bhaving a width of 20 to 40 mm may be used for the inspection, and a state of the film42on the inspection surface48having a plurality of shapes may be evaluated by one test piece. Further, in the present embodiment, an aluminum alloy is used as the base material of the test pieces52a,52b, but SUS, alumite, quartz, silicon carbide, and sintered yttria can be used. By using the same member as that used for the ground electrode40, the accuracy of the inspection can be improved.

A step of disposing the test piece and the ground electrode40of the present embodiment and forming the film42on these surfaces in parallel will be described with reference toFIG.7.FIG.7is a perspective view schematically showing a state where the ground electrode and the test pieces shown inFIGS.3A to6are disposed in a step of forming a film on an inner side wall of the ground electrode according to the present embodiment shown inFIG.2. The figure shows an arrangement of the ground electrode40and a test piece45when the film42having the plasma resistance is formed on the inner side wall and the upper end portion of the ground electrode40by an atmospheric plasma spraying (APS) method.

The APS method is a method of forming the film42on a surface of an object by spraying in an atmosphere at the atmospheric pressure. Raw material powder is melted by the plasma formed in the atmosphere, and the raw material in the molten or semi-molten state is sprayed on a surface of the object and laminated to form the film. At this time, a temperature of the object member (base material) whose surface is formed with the film is adjusted within a predetermined range, but in addition to a large amount of heat transferred from particles of the material of the film that is sprayed and fixed, heat is also radiated from the base material or the film through the atmosphere of the atmospheric pressure. Therefore, on the surface of the object that is sprayed and on which the film is formed, a history of heat transfer in the area and changes in the temperature and distribution due to the history are complicated, and it is necessary to devise a method for approximating the heat transfer and the temperature not only of the surface of the object but also during and after the formation of the film on the inspection surface48of the test piece.

Therefore, in the present embodiment, in order to approximate the heat transfer or the temperature and the change thereof, and the like on the inspection surface48of the test piece to those on a surface of an inner side wall member of the ground electrode40, at least one type of the test piece45among the test pieces53to56shown inFIGS.5and6is disposed to the ground electrode40having the ring or cylindrical shape and having an axially symmetrical cross section around the central axis in the up-down direction on the outer side wall surface of the end portion (the upper end portion in the case ofFIG.1) of the ground electrode40where the film42is formed to wrap around to the inner side wall surface and the outer side wall surface. Further, a sheet (not shown) having high thermal conductivity is sandwiched between the ground electrode40and the test piece45, and the test piece45is fixed to the ground electrode40using a mask tape. Further, the ground electrode40and the test piece45may be fixed with a double-sided tape having high thermal conductivity sandwiched therebetween.

On the outer side wall surface of the upper end portion of the ground electrode40, the mask tape is used to determine a range to be formed by covering a range where the film42is not formed. By covering an area of the outer side wall surface of the ground electrode40other than the area where the test piece is disposed by the mask tape, it is possible to prevent the film42from being formed on a portion other than a predetermined portion of the ground electrode40. As shown in the figure, a spray gun46is inserted in an inner peripheral side of the ground electrode40and is in a state in which a cylindrical blowout port that blows out a raw material of the spray gun46is held toward the inner wall surface at a predetermined angle (in the present embodiment, an angle between an axis of the blowout port from which particles of the raw material is blown out around a target and the central axis of the ground electrode40is 90 degrees), and the spray gun46is moved around the axis and in the axial direction at a predetermined radial position from the central axis while spraying and fixing the raw material to the inner side wall surface as shown by an arrow in the figure, and thus the film42is formed. Further, the spray gun46is moved outward at the upper end portion so as to be folded back from the upper end to the outer peripheral side, and is moved around the axis and in the axial direction at the predetermined radial position from the central axis, the film42is formed on the predetermined areas of the upper end surface and the outer side wall surface of the ground electrode40and the surface of the inspection surface48of the test piece45.

In a state where an inner peripheral wall surface of the opening43disposed on the side surface of the ring-shaped ground electrode40and a portion around the opening43on the outer side wall surface of the ground electrode40with which the seal member such as an O-ring of the gate valve50abuts are covered with the mask tape to prevent the film42from being formed thereon, the step of forming the film42on the ground electrode40is performed. In the present embodiment, a test piece installation jig47for the opening which serves as a lid is disposed on an inner side of the opening43, a position of the test piece installation jig47for the opening is fixed with respect to the ground electrode40using the mask tape, and the film42is formed on the inspection surface48on the test piece45and the ground electrode40.

The test piece installation jig47for the opening to which the test pieces45are connected using the double-sided tape having high thermal conductivity and whose position is fixed is inserted into the opening43, then the test piece installation jig47for the opening is fixed to the ground electrode40using the mask tape. While the spray gun46moves on a path similar to that of the inner side wall surface around the opening43, the raw material is sprayed to form the film42on the inner side wall surface of the ground electrode40and the surfaces of the test piece installation jig47for the opening and the test pieces45. That is, as if there is no opening43on the inner side wall surface of the ground electrode40, the spray gun46moves in an inner peripheral direction of the ground electrode40and in a direction along the vertical central axis, continues spraying under the same conditions as those of the inner side wall surface around the opening43, and blows out the raw material through the opening43. The surfaces of the test piece installation jig47for the opening and the test pieces45inside the opening43are sprayed.

Further, a ring-shaped test piece installation jig44is mounted on the lower end portion of the ground electrode40where the film42is not formed to the outer side wall surface. At least one type of the test piece45among the test pieces53to56shown inFIGS.5and6is disposed on an inner peripheral surface thereof. The film42is formed on the inspection surface48on an upper surface of the test piece45under the same conditions as the inner side wall surface of the upper ground electrode40. As on the upper end portion of the ground electrode40, the spray gun46may be folded back and moved from the inner peripheral side to the outer peripheral side at an lower end of the test piece installation jig44, so as to spray and form the film42to the outer side wall surface on the outer peripheral side. In this case, the test piece45can be inspected by forming the film42on the end portion of the ring-shaped member even the inspection surface48is provided on the end portion and the inner side and the outer side wall surfaces thereof.

Configurations of jigs on which the test pieces of the present embodiment are mounted will be described with reference toFIGS.8A to8C.FIGS.8A to8Cis a perspective view schematically showing a state where the test pieces according to the embodiment shown inFIG.5are mounted on the jigs.

As described above, in the step of forming the film42having the plasma resistance on the surface of the ground electrode40, the test pieces45such as the tip end portion shape test piece53, the projection inclined shape test piece54, and the recessed inclined shape test piece55are disposed adjacent to the ground electrode40, and the film42is formed on the inspection surfaces48in parallel. When each surface of the inspection surface48of each test piece is aligned with a surface of a corresponding portion of the ground electrode40, one test piece among these test pieces may have amounting surface that is not parallel to the central axis of the ground electrode40. For such a test piece, the test piece is mounted on an inclined test piece mounting jig57, and is further mounted on the jig in this state. The angle of the surface of the test piece mounted on the jig with respect to an axis of the blowout port of the spray gun46is similar to the angle of the surface with respect to the axis of the blowout port of the spray gun46at a portion of the inner side wall of the ground electrode40corresponding to the shape of the inspection surface48of the test piece.

As shown in a cross-sectional view ofFIG.8A, the projection inclined shape test piece54is fixed to a surface of a test piece surface57a, which is an inclined flat surface of the inclined test piece mounting jig57, by a male screw or a bolt. The male screw or the bolt is inserted from an opening on the opposite side of the test piece surface57aof a through hole opened to the test piece surface57aof the inclined test piece mounting jig57, and is screwed into a hole of a female screw opened on amounting surface of the projection inclined shape test piece54. The projection inclined shape test piece54is fixed in position on the test piece surface57aof the inclined test piece mounting jig57.

A plane, on which the opening on the opposite side of the test piece surface57aof the through hole of the screw or the bolt of the inclined test piece mounting jig57is disposed, is the outer side wall surface of the ground electrode40or a connection surface57bthat is connected to the test piece installation jig44and the test piece installation jig47for the opening by using the double-sided tape or the mask tape. As shown inFIG.8B, the recessed inclined shape test piece55is also connected to the test piece surface57a, which is an inclined flat surface of the inclined test piece mounting jig57, and is fixed using the male screw or the bolt inserted into the through hole from the opening on the mounting surface57b.

Further, as shown inFIG.8C, in the case of the tip end shape test piece53, the inspection surface48extends not only on one surface but also from a tip end surface to a back surface thereof, and the film42needs to be formed on these surfaces. Therefore, the tip end shape test piece53is configured such that an end portion opposite to the tip end portion can be inserted and mounted into or removed from a hole formed in a tip end shape test piece mounting jig58, and is configured to be fixed by screwing the screw or the bolt in a state where the tip end shape test piece53is inserted into the mounting hole of the tip end shape test piece mounting jig58.

The opening43can be considered as a portion where the test pieces45are disposed adjacently when the film is formed on the surface of the ground electrode40.

A state in which the test pieces45of the present embodiment are mounted on the jig will be described with reference toFIGS.9A and9B.FIGS.9A and9Bare perspective views schematically showing a state where the test pieces according to the present embodiment shown inFIGS.8A-8Care mounted on the jigs.

As shown inFIG.9A, the test pieces45of the present embodiment are disposed on a plurality of test piece mounting portions60, which are disposed on an inner side wall surface of the installation jig47for the opening and are made of the same material as the ground electrode40, with sheets having high thermal conductivity interposed, and the position of each test piece45is fixed by using the male screw or the bolt inserted from the outer side wall surface side of the installation jig47for the opening. The test piece45may be fixed by using the double-sided tape containing the material as a main material instead of the sheet having the high thermal conductivity.

In the figure, as in an example shown by left and center arrows, when the test piece45has a shape of such as the projection inclined shape test piece54or the recessed inclined shape test piece55, the test piece45is mounted on the inner side wall surface of the installation jig47for the opening with the inclined test piece mounting jig57interposed between the test piece installation jig47for the opening and the test piece45. In a state where the projection inclined shape test piece54and the recessed inclined shape test piece55are connected to the inclined flat test piece surface57aof the inclined test piece mounting jig57, the projection inclined shape test piece54and the recessed inclined shape test piece55are fastened and fixed in position by the male screws or the bolts inserted from the mounting surface57bon the opposite side, and in this state, the mounting surface57bis connected to the test piece mounting portion60and fixed in position.

On the other hand, as in an example shown by a right arrow in the figure, for the opening shape test piece56, when the central axis of the ground electrode40or the rotation axis of the spray gun46and a mounting surface of the opening shape test piece56are parallel, the opening shape test piece56may be connected to the test piece mounting portion60of the test piece installation jig47for the opening without another jig interposed and may be fixed by the screw or the tape.

Further,FIG.9Bshows a state where the test piece installation jig44having the same inner diameter and outer diameter as the ground electrode40is mounted on a lower end surface of the ground electrode40and a plurality of test pieces45is disposed on the inner peripheral surface of the test piece installation jig44. In this example, an inner peripheral wall surface of the test piece installation jig44has a cylindrical shape matching that of the ground electrode40when viewed from above at the same radial position around the axis in the up-down direction, but a mounting surface of the test piece45is a flat surface. Therefore, in a state where the mounting surface of the test piece45is directly connected to the inner peripheral wall surface of the test piece installation jig44, a gap may be generated therebetween.

In the present embodiment, in a state where a spacer made of the same material as the ground electrode40is mounted on the mounting surface of the test piece45, the test piece56or the spacer is fixed. Further, magnitudes and angles of inclination of the inspection surface48with respect to the central axis of the ground electrode40or a movement direction of the spray gun46and an axial direction of the blowout port are approximated to those of the corresponding positions of the ground electrode40, and the projection inclined shape test piece54and the recessed inclined shape test piece55are connected and fixed to the test piece installation jig44by using the inclined test piece mounting jig57.

The spray gun46can be configured to move from a state, where the blowout port is directed toward the inner peripheral side wall of the test piece installation jig44connected to the lower end portion of the ground electrode40, pass through the lower end to a portion facing the outer peripheral side wall surface and is folded back. Alternatively, the spray gun46can be moved in the opposite direction. Further, the lower portion of the test piece installation jig44has a recessed portion that is recessed from the inner peripheral side wall surface to the outer peripheral side and from the lower end surface to the upper side. The tip end shape test piece mounting jig58and the tip end shape test piece53are fitted into the recessed portion from below, and connected to the test piece installation jig44and fixed by using the screws or the bolts or the mask tape.

Further, the test piece installation jig44has a shape in which a thickness in the radial direction is larger than a thickness of the side wall portion of the ground electrode40mounted and connected above the upper end of the test piece installation jig44. By fitting and connecting the inclined test piece mounting jig57and the tip end shape test piece mounting jig58to the recessed portion, it is possible to reduce the heat radiation from these test pieces to the test piece installation jig44, and reduce deviation of histories of the heat transfer between the test piece45and the ground electrode40or deviation of histories of the temperature, and further reduce deviation of histories of the distribution thereof.

An example of a test piece installation jig61that further reduces the difference in the heat and the temperature value and the changes of the films42of the test piece45and the ground electrode40will be described with reference toFIGS.10A and10B.FIGS.10A and10Bare a perspective view and a cross-sectional view schematically showing another example of the test piece installation jig according to the embodiment shown inFIG.7.

The test piece installation jig61shown inFIG.10Ais a member that has a part having a cylindrical shape and is made of the same material as the ground electrode40. At least the inner peripheral side wall surface of a cross section62shown inFIG.10Bhas the same shape as that of the test piece52. Further, in a direction along the central axis in the up-down direction of the test piece installation jig61, distances from the axis to an inner peripheral side wall surface and an outer peripheral side wall surface have the same values as those of the ground electrode40. The test piece installation jig61has an inner diameter and an outer diameter which are the same as those of the ground electrode40.

The test piece installation jig61shown in the figure is viewed obliquely upward from a position spaced horizontally from the central axis in a state where a portion corresponding to the upper end portion of the ground electrode40is on the lower end, that is, the upper and lower positions are reversed. Further, the test piece installation jig61has at least one recessed portion which is recessed from the inner peripheral surface toward the outer peripheral side by a predetermined dimension, and the test piece45is fitted, mounted, and fixed into the recessed portion. In a state where the test piece installation jig61and the test piece45are connected and fixed with each other, the inspection surface48of the test piece45has a shape in which the inspection surface48and the inner wall surface of the test piece installation jig61around the inspection surface48have the same distances from the central axis or are close such that there is no step in heights at the end portion.

In a state where the test piece45, for example, the tip end shape test piece53, the recessed inclined shape test piece55, or the opening shape test piece56is directly fitted into the recessed portion or in a state of being mounted on the inclined test piece mounting jig57, the test piece45is fixed in position by inserting and fastening a male screw or a bolt from the outer peripheral side wall side of the test piece installation jig61. The test piece installation jig61in this state is disposed adjacent to the ground electrode40, the step of forming the film42on the inner side wall surface of the test piece installation jig61is performed in parallel with the step of forming the film42on the surface of the ground electrode40, and thus the film42is formed on the inspection surface48having each of the various shapes of the test pieces45under the same conditions as those of the inner side wall surface of the ground electrode40.

Further, a member for inspection, which has a ring or cylindrical shape having the same diameter as that of the ground electrode40, is made of the same material, and whose shape of a longitudinal cross section along the central axis is the same as or similar to that of the test piece52, can also be used as a test piece. In this case, the member for inspection having the ring or cylindrical shape has the same shape as the test piece installation jig61.

Such a ring-shaped or cylindrical test piece may be disposed on the lower end of the ground electrode40instead of the test piece installation jig44so as to be fixed in position, and the film42may be formed in parallel with the ground electrode40and the test piece. Thereafter, as shown inFIGS.5and6, apart having a shape of the inspection target is cut out from the ring-shaped or cylindrical test piece for inspection and the part is taken out as the test piece45, and the film42may be inspected. In this case, considering the ease of cutting work, a base material of the test piece having the ring or cylindrical shape is preferably an aluminum alloy, SUS, or alumite.

When the test piece installation jig44, or the test piece installation jig61, or the test piece having the same shape as the test piece installation jig61is disposed on the end portion of the ground electrode40or on the lower end portion of the ground electrode40shown inFIG.2, in the step of forming the film42, a gap is provided such that the test piece installation jig44or61or the test piece having the same shape as the test piece installation jig44or61is not connected to the ground electrode40by a sprayed raw material, which is important in reducing application of an unnecessary external force to the film42at other portions when the test piece installation jig44or61is separated from the ground electrode40after the step of forming the film42, and in improving the inspection accuracy.

In the above embodiment, an example in which the film42is formed by the atmospheric plasma spraying (APS) method is described. As other spraying techniques for forming the film42, there are techniques in the related art such as low-pressure spraying (LPPS, VPS), SPS spraying, and explosion spraying. These techniques differ in an atmosphere during spraying, a method of generating a plasma flame, a method of supplying raw material powder, and the like, but in the same technical scope, a step of forming a film is provided by placing raw material powder melted at a high temperature on a gas jet, and spraying and depositing the raw material powder on a target portion of a surface of a base material. In the step of forming the film42in the present embodiment, the same effect can be obtained by using a technique such as the low-pressure spraying (LPPS, VPS) instead of the atmospheric plasma spraying method.

Next, an example of forming the film42on the inner side wall of the processing chamber by using an aerosol deposition (AD) method, a cold spray method (CS), a sputter film formation (PVD), and the like will be described with reference toFIGS.11and12.FIG.11is a perspective view schematically showing a state where test pieces are mounted in a step of forming a film on an inner side wall of a ground electrode according to a modification of the embodiment shown inFIG.7.FIG.12is a perspective view schematically showing a state where the test pieces according to the modification shown inFIG.11are mounted on a test piece installation jig.

It is known that the AD method is a technique for forming a film in a vacuum, and the film is formed while adjusting a temperature of a base material to an appropriate temperature, but heat transfer during formation is relatively small. In the case of such an AD method, when the film42is formed on the test piece, a difference between a heat history of the inspection surface48and a heat history of the inner side wall surface of the ground electrode40is smaller than that of the technique of spraying such as the APS method.

Therefore, in the step of forming the film42on the inner side wall surface of the ground electrode40, the test piece45is disposed on the outer side wall of the end portion (the upper end portion in the case ofFIG.11) of the ground electrode40. On the upper end portion, the film42is formed on the inner side wall, the upper end surface, and the outer side wall by moving a film-forming gun63above the upper end and to the outer peripheral side in addition to the inner side of the inner side wall of the ground electrode40.

On the other hand, an area where the film42is formed on the outer peripheral side wall is defined by a mask tape, and the mask tape covers the outer side wall of the ground electrode40wider than an area where the test piece45is disposed such that the film42is not formed on an unnecessary position of the outer side wall of the ground electrode40. The surface of the area not covered by the film42is exposed to the supply of the material of the film42from the film-forming gun63, and the film42is formed.

The test piece45is fixed on the mask tape that covers the outer side wall of the ground electrode40, or is fixed by interposing a double-sided tape having high thermal conductivity therebetween. The film-forming gun63moves along the inner side wall in parallel with or around the central axis in the up-down direction and supplies the raw material to the inner wall surface of the ground electrode40by blowing out the raw material from the blowout port, and then forms the film42. Further, on the upper end portion, the film-forming gun63moves outward from above the upper end surface, folds back, and moves in parallel to the central axis or in a peripheral direction along the outer side wall surface. At the same time, the film42is formed on these surfaces including the inspection surface48of the test piece45.

When a film is formed by the aerosol deposition (AD) method, an AD film-forming gun is used as the film-forming gun63. In the case of using the cold spray method (CS), a cold spray gun is used as the film-forming gun63, and in the case of sputter film formation (PVD), an ion beam sputter gun is used as the film-forming gun63.

Further, the inner peripheral wall surface of the opening43disposed on the side wall of the ground electrode40is covered by the mask tape so as not to form the film42thereon. By using the portion covered by the mask tape, the test piece installation jig47for the opening, which is the lid of the opening43, is inserted inside the opening43, is connected to the ground electrode40by using the mask tape, and then is fixed in position. In a state where positions of the test piece45and the test piece installation jig47for the opening are fixed with respect to the ground electrode40, the film42is formed on the ground electrode40by spraying the raw material onto the surface of the ground electrode40while moving the film-forming gun63in a predetermined direction at a predetermined position.

Also in the example, in the step of forming the film42on the inner side surface of the ground electrode40, the film-forming gun63continues to blow out the raw material under the same conditions as the wall surface around the opening43even when the movement path of the film-forming gun crosses the opening43, and the film42is formed on the inspection surface48of the test piece45.

At the lower end portion of the ground electrode40of the example, the film42is formed up to the lowermost end of the inner side wall surface, while the film-forming gun63does not move to the lower end surface or the surface of the outer side wall connected to the lower end surface, so that the film42is not formed on these portions. Therefore, the ring-shaped test piece installation jig44shown inFIGS.9A and9Bor the test piece installation jig61shown inFIGS.10A and10Bmay be mounted on the lower end portion of the ground electrode40and the test piece45may be disposed on the inner side wall (inner peripheral wall surface). In this case, when the tip end shape test piece53is mounted on the jig, and the film42is formed on the inner side surfaces of the ground electrode40and the jig disposed below the lower end of the ground electrode40with a gap and the inspection surface48of the test piece45mounted on the jig as the upper end portion of the ground electrode40, the film-forming gun63is moved below the lower end of the jig, then is moved to the outer peripheral side of the outer side wall and folded back, and is moved along the outer side wall. Accordingly, the film42can be formed on the outer side wall surface and the inspection surface48on the test piece45including the tip end shape test piece53on the jig.

When the AD method, the CP method, the PVD method, or the like is used, since the temperature change at the portion where the film42is formed is relatively gentle, a simple ring-shaped test piece installation jig64as shown inFIG.12can be used. The test piece installation jig64has the same inner diameter as the lower end of the ground electrode40and a smaller outer shape, and has a ring shape whose length in the up-down direction is smaller than that of the test piece installation jig44. A plurality of test pieces45can be mounted on or removed from the inner peripheral wall surface of the test piece installation jig64.

Similar to the above example, the ring-shaped inner peripheral side wall surface of the test piece installation jig64shown in this figure has a cylindrical shape and is curved in the peripheral direction, whereas the mounting surface of the test piece45or the inclined test piece mounting jig57is a flat surface. Therefore, a spacer (not shown), which fills a gap between the test piece installation jig64and the test piece45or the inclined test piece mounting jig57when the two are connected, is made of the same material as the ground electrode, and is fixed by being interposed between the test piece45or the inclined test piece mounting jig57and the inner peripheral wall surface of the test piece installation jig64. In particular, when it is necessary to dispose the projection inclined shape test piece54and the recessed inclined shape test piece55with inclination, the projection inclined shape test piece54and the recessed inclined shape test piece55are fixed to the test piece installation jig64using the inclined test piece mounting jig57.

The test piece installation jig64of the example can fix the test piece45such that the test piece45protrudes from the lower end of the test piece installation jig64. The recessed portion that is recessed upward from the lower end portion of the test piece installation jig64is disposed, and the test piece45is inserted and fixed by using screws or bolts. By inserting the tip end shape test piece mounting jig58and the tip end shape test piece53into the recessed portion and fixing the tip end shape test piece mounting jig58and the tip end shape test piece53by screws or bolts or by a mask tape, the film42can be formed on the inspection surface48preset on the tip end portion (lower end portion in the figure) of the tip end shape test piece53protruding downward from the lower end portion of the test piece installation jig64by moving the film-forming gun63over the inner peripheral side, the tip end, and the outer peripheral side of the test piece installation jig64or the ground electrode40.

In an example shown inFIG.12, the test piece installation jig64is mounted on the lower end of the ground electrode40, and the test piece45is disposed and fixed with the tip end thereof protruding downward from the lower end portion of the test piece installation jig64. Therefore, the formation of the inspection surface48using the tip end shape test piece53that approximates the upper end portion of the ground electrode40having a portion where the film42is formed on the inner peripheral side and the outer peripheral side and the accuracy of the inspection of the film42on the tip end portion can be improved.

Also in the example, the test piece installation jig64is mounted on the end portion (the lower end portion in the above example) of the ground electrode40with a gap provided therebetween and the relative arrangement position is fixed. Therefore, it is similar to the above example in the point that an unnecessary external force can be prevented from being applied to the film42during film formation or removal so as to prevent the state of the film42from being different from that in the manufacturing process for mass production of the ground electrode40. However, in the example, the test piece installation jig64can be disposed with a gap smaller than that in the case of forming the film42using the APS method.

Next, an embodiment of the inspection is shown in FIGS.13and16. In the present embodiment, the film42formed on the inspection surface48of the test piece45by the above steps is inspected as a target for specific items. As the items, porosity, surface roughness (Ra), contamination (contaminant element), a crystallite size, a phase ratio, a residual stress after film formation and a post-treatment are detected, and it is determined whether a detection result is within a predetermined permissible range.

In the example, the porosity is detected by a liquid impregnation method. Further, the surface roughness (Ra) is detected by calculating an arithmetic square root of sum based on a result obtained by an atomic force microscope (AFm) having a long Z stroke or an optical surface texture measuring instrument (ZYGO). Further, the presence or absence of the contaminant element other than Y, O, F, and C is detected by fluorescent X-ray analysis.

On the other hand, the phase ratio is detected using X-ray diffraction. In the X-ray diffraction, integrated intensity of a diffracted X-ray from each crystal phase is detected with an incident angle fixed at 1° and 2θ within a range of 15° to 40°. The phase ratio is detected by a reference intensity ratio (RIR) method using the obtained integrated intensity. An average crystallite size is also detected using the X-ray diffraction. The X-ray diffraction from each crystal phase can be detected with the incident angle fixed at 1.5° and 2θ within the range of 10° to 100°. Each diffraction peak is indexed to obtain a half-width, and the average crystallite size is obtained by a Hall method. The residual stress is obtained using a 2θ−Sin 2ψ method, which is a residual stress measuring method using X-rays.

An example of a result of the inspection items obtained in this way will be described below with reference toFIG.13.

In the example, the films42having different average crystallite sizes are formed on the inspection surface48of any test piece45, each average crystallite size is detected, and a correlation between the average crystallite size and the number of generated foreign particles is examined. A result is shown inFIG.13.FIG.13is a graph showing the correlation between the average crystallite size and the number of the generated foreign particles of the film on the inspection surface of the test piece according to the present embodiment shown inFIGS.3A and3B. In the example of the figure, a relationship is shown in which the number of the generated foreign particles decreases as the average crystallite size decreases, which means that by reducing the average crystallite size of the material forming the film42, the generation of the foreign particles from the film42is reduced.

FIG.14is a graph showing a correlation between a hexagonal crystal phase ratio and the number of the generated foreign particles of the film on the inspection surface of the test piece according to the present embodiment shown inFIGS.3A and3B. The figure shows an example in which the films42having different hexagonal crystal phase ratios are formed on the inspection surface48of any test piece45, and the correlation between each hexagonal crystal phase ratio and the number of the generated foreign particles is examined. Also in the example, a correlation is shown in which the number of the generated foreign particles decreases as the hexagonal crystal phase ratio decreases. As described above, it can be seen that the crystallite size of the film42of the test piece45and the hexagonal crystal phase ratio (high temperature phase ratio) that increases as the temperature during formation increases are actually in the same state as the film42of the ground electrode40disposed inside the processing chamber7based on results shown inFIGS.13and14.

FIG.15is a graph showing changes in the average crystallite size and the hexagonal crystal phase ratio of the film with respect to a temperature change of a base material when the film is formed on the inspection surface of the test piece shown inFIGS.3A and3B. In the figure, the average crystallite size is indicated by a marker ● on a left axis, and the hexagonal crystal phase ratio is indicated by a marker ▪ on a right axis.

As shown in this figure, it is shown that the average crystallite size and the high temperature phase ratio obviously change with the temperature change of the surface of the base material. From the result of the figure and the results ofFIG.13andFIG.14, it is suggested that when the film42is formed, at a position where the temperature of the surface is changed, the number of the generated foreign particles is different from that of other positions where a temperature value or change is different. That is, it is assumed that, in the projection inclined shape test piece54or the recessed inclined shape test piece55, the number of the generated foreign particles is different from that of the film42of the tip end shape test piece53having a flat shape, for example.

This is because an angle between a spray direction of the spray gun46and a normal line of the surface of the ground electrode40can be controlled to some extent by multi-axis control of the spray gun. However, since the spray gun46moves along the central axis of the ground electrode40(or an axis assumed to be along the ground electrode40) to form the film42, in an area where an angle between the normal line of the surface of the ground electrode40and the central axis changes, for example, in a surface of a portion having a projection shape or a recessed shape, it is very difficult to make the angle or a distance between the spray gun46and the ground electrode40constant like other portions where the normal line is perpendicular to the central axis. Therefore, it is difficult to adjust a temperature of the surface during the formation of the film42at such a portion to be equal to those at other portions.

Further, at a projection portion of the projection inclined shape test piece54and an opening end of the opening shape test piece56, heat radiation during the formation of the film42tends to be relatively large as compared to other portions, and the temperature of the surface tends to be small. On the contrary, heat tends to be concentrated in the recessed portion of the recessed inclined shape test piece55and the tip end portion of the tip end shape test piece53, so that the temperature of the surface tends to be higher than other portions. As shown inFIG.15, it is assumed that the number of the generated foreign particles in such a portion is significantly different from those in other portions.

It is important for inspection and control to reproduce the formation of the film42under standard conditions by using a test piece having a flat plate shape that approximates a large area of the entire ground electrode40. However, in reducing the generation of the foreign particles inside the processing chamber7of the plasma processing apparatus100for manufacturing the semiconductor device, the entire area of the ground electrode40has the end portion of the film42, or a shape of the tip end portion, the projection portion or the recessed portion on which the film42is folded back and formed even if a ratio of these portions in the total area of the ground electrode40is small, but the angles of the surfaces (normal line) to the central axis of the ground electrode40at these portions are different from that of a portion along the direction of the central axis, and therefore these portions where the number of the generated foreign particles is different are important inspection and control point for predicting or reducing the number of the generated foreign particles.

FIG.16is a graph showing a correlation between the film which is on the inspection surface of the test piece according to the embodiment ofFIGS.3A and3Band in which the number of the generated foreign particles is different and a depth distribution of the residual stress. In the example, the residual stress is obtained using the 2θ−Sin 2ψ method, which is a residual stress measuring method using X-rays. In the usual 2θ−Sin 2ψ method, since a penetration depth of X-rays changes when ψ it is changed, in order to make the penetration depth of X-rays constant, detection is performed by adjusting an incident angle of X-rays and an inclination angle of the sample.

A longitudinal axis of the figure shows a magnitude of a compressive residual stress, and a lateral axis shows the penetration depth of X-rays under measured conditions. Data of the film42with a large amount of the generated foreign particles is indicated by the marker ●, data of the film42with a small amount of the generated foreign particles is indicated by the marker ▪, and data of the film42with a moderate amount of the generated foreign particles is indicated by a marker ⋄.

As shown in the figure, it can be seen that the film42in which the number of the generated foreign particles is small has a relatively large compressive residual stress as compared with the other examples. In particular, difference in the magnitude of the residual stress at a portion near the surface of the film42is more clearly seen.

It is known that the residual stress of the film42formed by APS spraying is generally small, but unlike the case where the film42is formed on a surface of a flat portion, in the projection portion of the projection inclined shape test piece54, the recessed portion of the recessed inclined shape test piece55, and the tip end portion of the tip end shape test piece53, the compressive residual stress decreases depending on temperature change (for example, cooling) after the film42is formed, and is in a state of a tensile residual stress. Since the residual stress of the film42at a portion having a complicated shape is in a residual stress state different from the residual stress at the portion having a flat shape, it is important to inspect the residual stress of the surface in order to inspect the quality of generated foreign particles of an inner wall material film.

It is possible to give the compressive residual stress to the portions of the film42having different residual stresses by applying chemical polishing or the like to the surface of the film42.

As in the above embodiment, for the film42formed on the inspection surface48of the test piece45in parallel with the step of forming the film42on the surface of the ground electrode40, parameters that are inspection items such as the porosity, the surface roughness (Ra), the crystallite size, the phase ratio, and the residual stress are detected, and it is determined whether values of these results are within the permissible range. The ground electrode40formed in the step in which the values are out of the permissible range is not used as a member of the processing chamber7. Alternatively, by adjusting conditions for forming the film42such that the inspection items fall within the permissible range and using the conditions as the conditions for forming the film42of the ground electrode40later, the quality of the film42formed on the surface of the ground electrode40can be controlled. By using such a ground electrode40and the manufacturing process thereof, it is possible to reduce the generation of the foreign particles in the processing chamber7of the plasma processing apparatus100and improve the processing yield of the wafer4. The ground electrodes40formed in a large number match the corresponding results of each inspection in a one-to-one relationship. The ground electrode40that has the film42with a large number of generated foreign particles is detected and selected. Therefore, highly accurate quality control is realized.

REFERENCE SIGN LIST

1: vacuum container2: shower plate3: window member4: wafer7: processing chamber6: stage8: gap9: through hole11: dry pump12: turbo molecular pump as exhaust unit13: impedance matching device14: high frequency power supply15: plasma16: pressure adjusting unit17: valve18: valve19: valve20: magnetron oscillator21: waveguide22: solenoid coil23: solenoid coil40: ground base material41: side wall member42: film43: opening44: test piece installation jig45: test piece46: spray gun47: test piece installation jig for opening48: inspection surface50: processing gas supply pipe51: valve52: test piece53: tip end shape test piece54: projection inclined shape test piece55: recessed inclined shape test piece56: opening shape test piece57: inclined test piece mounting jig58: tip end shape test piece mounting jig60: test piece mounting portion laid with highly conductive sheet61: test piece installation jig62: cross-sectional shape of test piece installation jig63: film-forming gun64: simple ring-shaped test piece installation jig75: pressure sensor