JP2013187320A - Inline type plasma cvd device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inline type plasma CVD device which uniformly forms a plasma CVD film in a film formation chamber, eliminates contamination of a plate due to a film formation material in the film formation chamber, and simplifies and facilitates a cleaning process.SOLUTION: In a film formation chamber 3 of an inline type plasma CVD device, a substrate 12 placed on a plate 11 is positioned between an electrode 10 and a heater 7 which are placed at the center of the film formation chamber 3 in a plane view. The heater 7 is moved up by a support member 8, and the plate 11 is placed in contact with a facing electrode to be connected therewith. Then, a material gas is jetted from pores 10b of the electrode 10 and an electrical current is discharged between the electrode 10 and the plate 11 to form a predetermined film on the substrate 12. An exhaust gas is exhausted from exhaust ports 30 provided at positions on a bottom wall of the film formation chamber 3 that are set by dividing a periphery of a center part of the bottom wall into quarters.

Description

  In the present invention, a large number of substrates on a plate are placed in a load chamber together with the plate, evacuated, and then sequentially moved to a preheating chamber, a film formation chamber, and an unload chamber, and then the atmosphere is set in the unload chamber The present invention relates to an in-line type plasma CVD apparatus for collecting a substrate after film formation, and relates to an in-line type plasma CVD apparatus and method capable of gas cleaning a plate used for film formation.

  A plasma CVD (chemical vapor deposition) apparatus is a semiconductor device in which a silicon nitride film (SiNx film) is formed on a Si substrate to manufacture a solar cell, and various semiconductor layers are formed on the Si substrate. Is often used in the manufacture of This plasma CVD apparatus supplies a source gas to a substrate atmosphere in a state where a substrate placed on a plate is heated to, for example, 500 ° C. in a vacuum, and generates a plasma discharge between the electrode and the substrate. Then, after ionizing the source gas, a predetermined component is deposited on the substrate to form a desired film. As this plasma CVD apparatus, a plate on which a substrate is placed is loaded into the load chamber from the atmosphere, and the load chamber is vacuumed to bring the substrate into a vacuum atmosphere, and then the vacuum is broken. Rather, the substrate is moved from the preheating chamber to the film formation chamber, the substrate after film formation is transferred to the unload chamber, and the inside of the unload chamber is brought into the atmosphere to take out the substrate after film formation. A plasma CVD apparatus has been proposed (Patent Document 1). As described above, since the substrate can be heated and formed in a series of steps without breaking the vacuum, the in-line type plasma CVD apparatus has an advantage of high throughput.

JP 2010-159463 A

  However, the conventional in-line type plasma CVD apparatus has a problem that it is difficult to uniformly form a plasma CVD film on a large number of substrates placed on a plate. When the film is contaminated with a film forming material, the inner surface and the plate of the film forming chamber are cleaned by wet cleaning, and this cleaning process takes time.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an in-line type plasma CVD apparatus capable of forming a plasma CVD film uniformly in a film forming chamber. Another object of the present invention is to provide an in-line type plasma CVD apparatus capable of simplifying and speeding up a cleaning process by performing contamination of a plate with a film forming substance in a film forming chamber.

The in-line type plasma CVD apparatus according to the first invention of the present application includes a load chamber and an unload chamber capable of opening the atmosphere to the atmosphere and vacuum suction, a preheating chamber for heating the internal charge in a vacuum state, and an internal device. A film forming chamber for forming a film by plasma CVD in a vacuum state with respect to the incoming material,
After the plate on which a plurality of substrates are placed is evacuated in the load chamber, the substrate on the plate is heated by being inserted into the preheating chamber while maintaining this vacuum state, While maintaining the vacuum state, the film is inserted into the film formation chamber and formed on the substrate on the plate by plasma CVD. After being released from the vacuum state to the atmosphere in the unload chamber, the film is formed on the plate. In an in-line type plasma CVD apparatus from which the substrate is taken out,
A supply unit for supplying a discharge target to a discharge position set at a central portion in plan view in the film forming chamber;
An electrode disposed above the discharge position in the deposition chamber;
A heater disposed below the discharge position in the film forming chamber;
An introduction member for introducing a raw material gas or a cleaning gas into the film formation chamber from a position immediately above the discharge position on the upper surface in the film formation chamber;
A power source for generating a plasma discharge by applying a plasma discharge voltage between the electrode and the discharge target;
A plurality of gas exhaust ports installed at a plurality of equally spaced positions around a position directly below the discharge position on the lower surface of the film forming chamber;
It is characterized by having.

  In this invention, it is preferable to have a drive member which moves the said discharge target object up and down within the said film-forming chamber.

The in-line type plasma CVD apparatus according to the second invention of the present application is
A load chamber and an unload chamber capable of opening the atmosphere to the atmosphere and vacuum suction, a preheating chamber for heating the internal charge in a vacuum state, and forming a film on the internal charge by plasma CVD in a vacuum state A deposition chamber;
After the plate on which a plurality of substrates are placed is evacuated in the load chamber, the substrate on the plate is heated by being inserted into the preheating chamber while maintaining this vacuum state, While maintaining the vacuum state, the film is inserted into the film formation chamber and formed on the substrate on the plate by plasma CVD. After being released from the vacuum state to the atmosphere in the unload chamber, the film is formed on the plate. In an in-line type plasma CVD apparatus from which the substrate is taken out,
A supply unit for supplying a discharge target to a discharge position in the film forming chamber;
An electrode disposed above the discharge position in the deposition chamber;
A heater disposed below the discharge position in the film forming chamber;
A drive member that moves the discharge object up and down in the film forming chamber;
An introduction member for introducing a source gas or a cleaning gas into the film forming chamber;
A power source for generating a plasma discharge by applying a plasma discharge voltage between the electrode and the discharge target;
It is characterized by having.

  The discharge object is placed on a placement unit in the film forming chamber, and the driving member raises the heater to contact the discharge object, and further raises the heater. The discharge object can be lowered on the mounting portion by lifting the discharge object, raising it, and lowering the heater. In this case, the drive member has a support member that hermetically inserts the lower wall of the film forming chamber, and the heater is supported by the upper end portion of the support member, and the support member moves up and down. Thus, the heater can be configured to move up and down.

  The two film forming chambers are arranged in series, and different types of films can be formed in each film forming chamber.

In-line type plasma CVD method according to the present invention,
Using any of the above-mentioned inline-type plasma CVD apparatus,
When a plate on which a substrate is placed is supplied as an object to be discharged in the film formation chamber, the film is formed on the substrate by the source gas and the plasma discharge,
When the discharge target plate is supplied as a discharge target, the deposit on the plate is removed by the cleaning gas and the plasma discharge,
When removing the deposit on the plate, the plate is moved closer to the electrode by raising the plate by the driving member than when depositing on the substrate.

  According to the first invention of the present application, in the film forming chamber for forming a film on the substrate on the plate by plasma CVD, the plate (discharge target) on which the substrate is placed is set at the center in a plan view in the film forming chamber. The raw material gas is introduced into the film forming chamber from a position immediately above the discharge position, and the gas in the film forming chamber is arranged at a plurality of points with equal distribution around the position immediately below the discharge position. Exhaust from a plurality of gas exhaust ports installed at the position. For this reason, when the flow of the source gas is made uniform in the film formation chamber and the electrode is energized to generate a discharge, the film can be uniformly formed on the substrate on the plate.

  Further, in the second invention of the present application, an empty plate after film formation processing on which no substrate is placed is installed, for example, the plate height is set higher than the plate position at the time of film formation, In a state where the distance from the plate is shortened, the cleaning gas is supplied into the film forming chamber and this cleaning gas is plasma-discharged to remove the deposits (contaminants) on the used plate. Thereby, a used plate can be easily cleaned in the in-line chamber.

  Then, according to the present invention, the plate is gas-cleaned in the chamber, and the deposit on the inner surface of the film-forming chamber may be removed by wet cleaning once every several times of gas cleaning. The cleaning process can be simplified and quicker than when the plate is also wet-cleaned.

It is a block diagram which shows the in-line type plasma CVD apparatus of embodiment of this invention. It is a figure which shows the internal structure (at the time of film-forming) of the film-forming chamber. It is a figure which shows the drive member which moves a heater up and down. 3 is a bottom view showing an exhaust unit provided outside the bottom surface of the film forming chamber 3. FIG.

  Hereinafter, embodiments of the present invention will be specifically described with reference to attached drawings. As shown in FIG. 1 and FIG. 2, the in-line type plasma CVD apparatus has a plate 11 on which a plurality of Si substrates 12 are placed as a film formation target, that is, a discharge target that receives plasma discharge, in the atmosphere. After the inside of the load chamber 1 is charged and the inside is sealed, the inside of the load chamber 1 is vacuumed to bring the substrate 12 and the plate 11 into a vacuum atmosphere. Thereafter, the plate 11 on which the substrate 12 is placed is moved and loaded into the preheating chamber 2 without breaking the vacuum state, and the substrate 12 and the plate 11 are heated in the preheating chamber 2. When forming a SiN film on the Si substrate 12, the substrate 12 is heated to, for example, about 500 ° C. in the preheating chamber 2.

  Thereafter, the substrate 12 and the plate 11 are moved from the preheating chamber 2 into the film forming chamber 3 while being kept in a vacuum state, and the source gas is supplied into the chamber in the film forming chamber 3. While heating the substrate 12 and the plate 11 to be formed, plasma discharge is generated between the plate 11 and the electrode 10 to ionize the film forming gas. Thereby, a desired film is deposited on a discharge target such as a substrate. After that, the discharge target after film formation is moved from the film formation chamber 3 to the unload chamber 4 with the vacuum state maintained, and the unload chamber 4 and the film formation chamber 3 are shut off. Then, the unload chamber 4 is opened to atmospheric pressure, and the film formation target after film formation is taken out. Thus, in the in-line type plasma CVD apparatus, the substrate is heated and formed in a series of steps without breaking the vacuum.

  The substrate 12 is placed on the plate 11 and sequentially loaded into each chamber. That is, as shown in FIG. 2, for example, a plurality of Si substrates 12 constituting, for example, a solar battery cell are mounted on a graphite carbon plate 11. The plate 11 has a size of, for example, about 1500 mm × 1100 mm. On the plate 11, for example, a Si substrate 12 having a size of, for example, 156 mm × 156 mm is equally spaced at a matrix position of, for example, 6 rows and 9 columns. Are placed under certain rules.

  The plate 11 is placed on the pulley 13, and is sequentially transferred into the load chamber 1, the preheating chamber 2, the film forming chamber 3, and the unload chamber 4 by the rotation of the pulley 13. Note that the preheating and film formation are performed while the plate 11 is stopped in each chamber.

  As shown in the bottom view of FIG. 4, the film forming chamber 3 has a rectangular shape whose bottom surface is slightly horizontally long, and has a box shape as a whole. A box-shaped electrode 10 having an internal space is installed in the upper part of the film forming chamber 3, and a source gas or cleaning gas introduction pipe 6 is installed through the top wall of the film forming chamber 3. The gas introduction pipe 6 communicates with the inside of the electrode 10. The electrode 10 is disposed at the center of the film forming chamber 3 in plan view. A source gas or cleaning gas supply unit 5 is installed outside the film forming chamber 3 so that the source gas or the cleaning gas is supplied from the supply unit 5 into the electrode 10 through the introduction pipe 6. It has become. The electrode 10 is arranged so that the lower wall 10a thereof is horizontal, and a plurality of pores 10b are formed in the lower wall 10a, and the gas in the electrode 10 is transferred from the pores 10b to the electrode 10. It is designed to spout downward.

  A heater 7 is installed below the film forming chamber 3 so as to face the electrode 10. This heater 7 is also arranged in the center of the film forming chamber 3 in plan view. The heater 7 is supported by an upper end portion of a support member 8 that is hermetically inserted through the lower wall of the film formation chamber 3. The heater 7 moves up and down in the film formation chamber 3 by moving the support member 8 up and down. can do. 2 and 3 is a bellows for performing the vertical movement of the support member 8 in an airtight manner.

  The heater 7 has, for example, a resistance heating wire, such as an Inconel's heater, installed between an upper plate and a lower plate made of Ni or Ni alloy, and the resistance heating wires are insulated from each other by an insulating spacer. Is fixed to the upper plate and the lower plate by, for example, screwing. FIG. 3 is a view showing a vertical mechanism of the heater 7 and a method of supplying power from the outside. The support member 8 inserted through the film forming chamber 3 can be moved up and down by a bellows 9 provided on the lower surface of the film forming chamber 3 so that the vacuum in the film forming chamber 3 is not broken. Further, a cylindrical member 21 is installed so as to be vertically movable so as to pass through the lower wall of the film forming chamber 3, and this cylindrical member 21 is surrounded by a bellows 22 provided in the film forming chamber 3. Thus, the vacuum state of the space in the film forming chamber 3 is not broken between the outer surface of the cylindrical member 21 and the film forming chamber 3. And the sealing member 23 is airtightly inserted in the inside of the cylinder member 21, and the lead wire 24 connected to the outside is inserted through the inside of the sealing member 23. Thereby, the vacuum state in the film forming chamber 3 is held by the bellows 22 and the sealing member 23. Further, the lead wire 24 is connected to the heater 7.

  The plate 11 transferred from the preheating chamber 2 into the film forming chamber 3 is placed on the pulley 13 and is rotated between the electrode 10 in the film forming chamber 3 and the heater 7 by the rotation of the pulley 11. Supplied. A plurality of substrates 12 are placed on the plate 11, and the substrate 12 is heated to a predetermined set temperature of, for example, 400 to 500 ° C. in the preheating chamber 2. The film forming chamber 3 is also heated and held at this set temperature by the heater 7 supplied with power from the outside of the chamber through the lead wires 24. The plate 11 on which the substrate 12 is placed is placed between the electrode 10 and the heater 7 at the time of discharge. Therefore, the plate 11 is also placed at the center of the film forming chamber 3 in plan view at the time of discharge. The discharge position is at the center of the film forming chamber 3.

  On the lower wall of the film forming chamber 3, as shown in FIG. 4, four exhaust ports 30 are arranged at four equal positions with a central portion 31 located in the center of the film forming chamber 3 in plan view. is set up. That is, each exhaust port 30 penetrating the bottom wall of the film forming chamber 3 communicates with the collective portion 31 via the exhaust pipe 32, and the collective portion 31 is connected to an external exhaust pump via the pipe 33. Yes. These exhaust pipes 32 are of equal length, and the gas in the film forming chamber 3 discharged from each exhaust port 30 gathers in the collecting portion 31 through the equal-sized exhaust pipe 32 and is sucked in through the pipe 33. Therefore, the exhaust gas from each exhaust port 30 is exhausted through the same path.

  In addition, each of the exhaust ports 30 has the same distance from the pair of long side walls which are the long side surfaces of the film forming chamber 3, and the pair of the short side surfaces of the film forming chamber 3. The distance from the short side wall is the same. Accordingly, the opening angles of the four exhaust pipes 32 that open toward the two long side walls are the same, and the opening angles that open toward the two short side walls are the same. Therefore, the gas flow of the raw material gas supplied from the electrode 10 is discharged under equivalent conditions with respect to all the exhaust ports 30 with respect to the discharge position (the plate 1 installed in the center) set in the center of the film forming chamber 3. The exhaust gas flow is uniform.

  Further, each exhaust port 30 is provided with a rectifying plate 34, and all exhaust gas from the film forming chamber 3 passes through the rectifying plate 34 and is discharged. This prevents the gas flow from being disturbed in the film forming chamber 3 in the vicinity of the exhaust port 30 of the film forming chamber 3.

  Next, the operation of the inline type plasma CVD apparatus configured as described above will be described. At the time of film formation, as shown in FIG. 2, the plate 11 on which the substrate 12 is placed is supplied into the film formation chamber 3, and the substrate 12 and the plate 11 are positioned at the discharge position between the electrode 3 and the heater 7. Let Then, the support member 8 is raised to raise the heater 7, and the heater 7 is brought into direct contact with the plate 11, or is brought into contact with the plate 11 via an appropriate buffer. Thereafter, the heater 7 is further raised to lift the plate 11, the plate 11 is brought into contact with the counter electrode (not shown) of the discharge electrode 10 installed in the film forming chamber 3, and the plate 11 is connected to the counter electrode. Then, a raw material gas for a film to be formed from the gas supply unit 5, for example, a mixed gas of ammonia gas and monosilane gas is introduced into the electrode 10 through the introduction pipe 6, and the substrate 12 is introduced from the pores 10 b of the electrode 10. Raw material gas is spouted toward Further, the substrate 12 on the plate 11 is heated by the heater 7 and maintained at a predetermined film forming temperature. Along with the supply of the source gas, a discharge voltage is applied between the electrode 10 and the plate 11 connected to the counter electrode to cause plasma discharge of the source gas in the film forming chamber 3, so that a film is formed on the substrate 12. Deposit raw material. At this time, the film formation quality depends on the distance between the electrode 10 and the substrate 12 on the plate 11, and it is necessary to secure this distance to some extent. Therefore, the plate 11 is positioned at a position not very close to the electrode 10. It is necessary to cause discharge.

  Thus, in the present invention, the source gas introduced into the film forming chamber 3 from the gas supply unit 5 is jetted into the film forming chamber 3 from the electrode 10 disposed at the center of the film forming chamber 3. Exhaust gas is sucked out through a pipe 33 connected to an external exhaust means through an exhaust port 30 provided at an evenly spaced position from the bottom center at the bottom of the membrane chamber 3. Since the exhaust gas is sucked from each exhaust port 30 through the isometric exhaust pipe 32 to the collecting portion 31 at the tip of the pipe 33, the flow rate of the exhaust gas discharged from each exhaust port 30 is set to each exhaust port. 30 is constant. For this reason, the gas flow in the film forming chamber 3 is uniform in the film forming chamber 3. Further, since the rectifying plate 34 is installed at the exhaust port 30, there is no disturbance of the gas flow when the exhaust gas is discharged from each exhaust port 30.

  Thus, since the flow of the source gas is uniform in the film forming chamber 3 and there is no turbulent portion, a very uniform film is formed on each substrate 12 on the plate 11 by plasma discharge. A homogeneous film (for example, a SiNx film) can be formed.

On the other hand, at the time of cleaning, as shown in FIG. 3, only the plate 11 used for the film forming process and attached with the discharge substance is positioned at the discharge position in the film forming chamber 3. Then, the heater 7 is energized to heat the plate 11 to a predetermined temperature, the support member 8 is raised, and the heater 7 is brought into direct contact with the plate 11 or via an appropriate buffer to the plate 11. Further, the support member 8 is raised, the plate 11 is lifted by the heater 7, and the plate 11 is brought into contact with the counter electrode in the film forming chamber 3. Further, the plate 11 is raised and brought closer to the electrode 10. Thereafter or while the plate 11 is raised, for example, NF ₃ gas is introduced into the electrode 10 as a cleaning gas, and this cleaning gas is ejected from the pores 10 b of the electrode 10 toward the plate 11. Then, a discharge voltage is applied between the electrode 10 and the counter electrode to cause discharge of the cleaning gas between the electrode 10 and the plate 11, and the deposits or contaminants on the plate 11 are discharged by the discharge of the cleaning gas. Remove. In addition, the discharge period required for this cleaning can be significantly shortened compared with the discharge period at the time of film formation by making the interval between the electrode 10 and the plate 11 shorter than the interval at the time of film formation.

  In this case, at the time of film formation, the plate 11 is placed at a position separated from the electrode 10 by, for example, 40 mm, but at the time of cleaning, it is not necessary to consider the uniformity of film formation and the film formation quality. From 10 to a position of 20 mm, for example. As a result, a strong discharge can be caused to quickly remove the deposits or contaminants on the plate 11 and the electrode 10.

  Even during this cleaning, since the flow of the cleaning gas in the film forming chamber 3 is uniform, unnecessary adhering substances at the time of film forming can be uniformly removed from the plate 11 used for the film forming process.

  In the present invention, the plate 11 after the film formation process can be cleaned in a vacuum without dropping the vacuum in the film formation chamber 3, so that the deposits or contaminants can be quickly removed from the plate 11. can do. Since the plate 11 is gas-cleaned in this way, each time this gas cleaning is performed a plurality of times, the inside of the film forming chamber 3 may be wet-cleaned once, so that the processing time of the entire cleaning can be significantly shortened. It can be simplified.

  In the above embodiment, the plasma CVD film can be uniformly formed in the film forming chamber, and the contamination of the plate with the film forming material is performed in the film forming chamber to simplify and speed up the cleaning process. However, if the homogenization of the plasma CVD film is not a problem, it is not necessary to set the discharge position at the center in a plan view in the film forming chamber, and a plurality of gas exhausts It is not necessary to install the mouths at a plurality of positions that are equidistant around the position immediately below the discharge position on the lower surface of the film forming chamber.

1: Load chamber 2: Preheating chamber 3: Film formation chamber 4: Unload chamber 8: Support member 9, 22: Bellows 10: Electrode 11: Plate (made of graphite carbon)
12: Substrate (Si substrate)
13: Roller 21: Tube member 23: Sealing member 24: Lead wire 30: Exhaust port 31: Collecting part 32: Exhaust pipe 33: Pipe 34: Current plate

Claims (7)

A load chamber and an unload chamber capable of opening the atmosphere to the atmosphere and vacuum suction, a preheating chamber for heating the internal charge in a vacuum state, and forming a film on the internal charge by plasma CVD in a vacuum state A deposition chamber;
After the plate on which a plurality of substrates are placed is evacuated in the load chamber, the substrate on the plate is heated by being inserted into the preheating chamber while maintaining this vacuum state, While maintaining the vacuum state, the film is inserted into the film formation chamber and formed on the substrate on the plate by plasma CVD. After being released from the vacuum state to the atmosphere in the unload chamber, the film is formed on the plate. In an in-line type plasma CVD apparatus from which the substrate is taken out,
A supply unit for supplying a discharge target to a discharge position set at a central portion in plan view in the film forming chamber;
An electrode disposed above the discharge position in the deposition chamber;
A heater disposed below the discharge position in the film forming chamber;
An introduction member for introducing a raw material gas or a cleaning gas into the film formation chamber from a position immediately above the discharge position on the upper surface in the film formation chamber;
A power source for generating a plasma discharge by applying a plasma discharge voltage between the electrode and the discharge target;
A plurality of gas exhaust ports installed at a plurality of equally spaced positions around a position directly below the discharge position on the lower surface of the film forming chamber;
An in-line type plasma CVD apparatus characterized by comprising: The in-line type plasma CVD apparatus according to claim 1, further comprising a drive member that moves the discharge object up and down in the film forming chamber. A load chamber and an unload chamber capable of opening the atmosphere to the atmosphere and vacuum suction, a preheating chamber for heating the internal charge in a vacuum state, and forming a film on the internal charge by plasma CVD in a vacuum state A deposition chamber;
After the plate on which a plurality of substrates are placed is evacuated in the load chamber, the substrate on the plate is heated by being inserted into the preheating chamber while maintaining this vacuum state, While maintaining the vacuum state, the film is inserted into the film formation chamber and formed on the substrate on the plate by plasma CVD. After being released from the vacuum state to the atmosphere in the unload chamber, the film is formed on the plate. In an in-line type plasma CVD apparatus from which the substrate is taken out,
A supply unit for supplying a discharge target to a discharge position in the film forming chamber;
An electrode disposed above the discharge position in the deposition chamber;
A heater disposed below the discharge position in the film forming chamber;
A drive member that moves the discharge object up and down in the film forming chamber;
An introduction member for introducing a source gas or a cleaning gas into the film forming chamber;
A power source for generating a plasma discharge by applying a plasma discharge voltage between the electrode and the discharge target;
An in-line type plasma CVD apparatus characterized by comprising: The discharge object is placed on a placement unit in the film forming chamber, and the driving member raises the heater to contact the discharge object, and further raises the heater. 4. The in-line plasma CVD according to claim 2, wherein the discharge object is lowered by raising the discharge object, raising the discharge object, and lowering the heater to lower the discharge object onto the mounting portion. apparatus. The drive member includes a support member that hermetically inserts the lower wall of the film forming chamber, and the heater is supported by an upper end portion of the support member. By moving the support member up and down, the heater The in-line type plasma CVD apparatus according to claim 4, which is moved up and down. The in-line according to any one of claims 1 to 3, wherein two film forming chambers are arranged in series, and different types of films are formed in each film forming chamber. Type plasma CVD equipment. Using the in-line type plasma CVD apparatus according to any one of claims 2 to 5,
When a plate on which a substrate is placed is supplied as an object to be discharged in the film formation chamber, the film is formed on the substrate by the source gas and the plasma discharge,
When the discharge target plate is supplied as a discharge target, the deposit on the plate is removed by the cleaning gas and the plasma discharge,
When removing deposits on the plate, the plate is moved up by the driving member to bring the plate closer to the electrode than in the case of forming a film on the substrate. .

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