WO2022009340A1

WO2022009340A1 - Cover member for plasma processing device, plasma processing, and membrane production method

Info

Publication number: WO2022009340A1
Application number: PCT/JP2020/026716
Authority: WO
Inventors: 和浩上田; 和幸池永; 誠浩角屋
Original assignee: 株式会社日立ハイテク
Priority date: 2020-07-08
Filing date: 2020-07-08
Publication date: 2022-01-13

Abstract

Provided are a plasma processing device that reduces the generation of particles and improves processing yield, a cover member for the plasma processing device, and a membrane production method. The present invention includes a membrane that is formed by spraying a plurality of particles of yttrium oxide and yttrium fluoride and covers an inner surface of a grounding electrode 40 disposed on an inner wall of a processing chamber that is arranged inside a vacuum container and in which a plasma is formed, the inner surface of the grounding electrode 40 being exposed to the plasma. The spraying is performed at a thermal spray temperature that is higher than the melting point of the yttrium fluoride material and lower than the melting point of the yttrium oxide material. The yttrium fluoride material is melted between a plurality of crystals of the yttrium oxide material and then recrystallized and solidified, and the yttrium oxide crystals are adhered to obtain the membrane. The average size of each of the crystallites constituting the membrane is 50 nm or less.

Description

Manufacturing method of cover member, plasma processing and coating of plasma processing equipment

The present invention relates to a cover member for a plasma processing device, a plasma processing device, and a method for manufacturing a coating film.

In the process of processing a semiconductor wafer to manufacture an electronic device or a magnetic memory, plasma etching is used for fine processing for forming a circuit structure on the surface of the wafer. Such processing by plasma etching is required to have higher accuracy and yield as the device becomes highly integrated.

In the plasma processing apparatus used for plasma etching, a processing chamber is arranged inside the vacuum vessel, and metal materials such as aluminum and stainless steel are usually used for the internal members of the processing chamber from the viewpoint of strength and cost. Further, since the surface of the internal member of the processing chamber is exposed to the formed plasma, a highly plasma-resistant coating film is arranged on the surface of the internal member, and the surface of the internal member is not worn by the plasma. In general, it is configured so that changes in the amount and properties of the interaction between the plasma and the surface of the internal member are suppressed.

Patent Document 1 discloses an example of a plasma-resistant coating used for an internal member of such a processing chamber. In Patent Document 1, a film of yttrium oxide is shown as an example of the above-mentioned film.

Generally, the coating film using yttrium oxide is either vacuum or atmospheric by a method such as plasma spraying, SPS spraying, explosive spraying, or vacuum spraying (hereinafter, these methods are referred to as "thermal spraying" in the present disclosure). It is known that it can be formed even in an atmosphere. In the atmospheric plasma spraying method, raw material powder having a predetermined particle size, for example, a diameter in the range of 10 to 60 μm, is introduced into a plasma flame together with a transport gas to be in a molten or semi-melted state, and the raw material particles in such a state are obtained. Is a technique for forming a film by spraying the surface of a base material to be coated. On the other hand, in this thermal spraying method, the height on the surface of the formed coating film, that is, the fluctuation of so-called unevenness is large, and moreover, the particles of the coating film that are adhered to each other in a molten or semi-molten state and are cooled and solidified. Pore is formed between them, and there is a problem that particles of gas or product in plasma enter the pore and induce contamination or foreign matter.

For such problems, many solutions have been studied conventionally, as disclosed in the disclosures in Patent Document 2 and Patent Document 3, for example. These patent documents disclose the so-called aerosol deposition method. In this technology, raw material powder having a diameter of about several μm is sprayed onto the surface of the substrate to be coated at a speed close to the speed of sound to form a film, and a layered structure consisting of microcrystals having a size of 8 to 50 nm is formed. Is formed as a film, and it is said that the surface irregularities can be made smaller than those of the above-mentioned atmospheric plasma spraying method.

By the way, when the film made of yttrium oxide is exposed to the plasma of a fluorine-based gas, it reacts with fluorine or the like in the plasma, and there is a problem that the film is easily worn. Therefore, it is being considered to change the coating to yttrium fluoride. Patent Document 4 discloses a technique for forming this yttrium fluoride film by a thermal spraying method using plasma under atmospheric pressure.

Furthermore, in the formation of the yttrium fluoride film, studies are underway to suppress cracks, reduce surface roughness, and improve pressure resistance. Patent Document 5 discloses a range of values of a specific mixing ratio of yttrium fluoride granulated powder and yttrium oxide granulated powder as a thermal spraying material capable of obtaining a thermal spray coating of an yttrium-based fluorocompound. There is. By using the coating material of the thermal spray material adjusted in this way, it is possible to have sufficient corrosion resistance against plasma and effectively prevent damage to the base material due to acid permeation even during cleaning with acid.

Further, Patent Document 6 discloses a technique for producing a thermal spray coating made of yttrium fluoride that can suppress the generation of particles. The disclosed technique is a nozzle of a thermal spray gun that emits a frame in a high-speed frame thermal spraying method, or a nozzle of the thermal spray gun in a direction along the central axis of a thermal spray gun nozzle that emits a plasma jet in an atmospheric pressure plasma spraying method. A slurry containing particles of yttrium fluoride having an average particle size in a specific range is supplied to a position distant from the downstream side or a position at the tip of the nozzle.

Japanese Patent No. 4006596 Japanese Unexamined Patent Publication No. 2014-141390 Japanese Unexamined Patent Publication No. 2016-27624 Japanese Unexamined Patent Publication No. 2013-140950 Japanese Unexamined Patent Publication No. 2017-190475 Japanese Unexamined Patent Publication No. 2017-15805 Japanese Unexamined Patent Publication No. 2019-192701

However, in the above-mentioned conventional technology, the following points were not sufficiently considered, which caused a problem. That is, as the processing accuracy required for the plasma processing apparatus used for plasma etching increases, the influence of foreign matter having a small diameter generated during processing in the processing chamber arranged inside the vacuum vessel is also regarded as a problem. As described above, it is required to suppress the generation of fine particles having a smaller diameter.

In the above-mentioned conventional technique using yttrium fluoride as a film material, the conditions for forming a thermal sprayed film capable of sufficiently suppressing corrosion and generation of fine particles have not been sufficiently considered. Further, although

Patent Documents

2 and 3 disclose the conditions of the coating film arranged on the surface of the member constituting the treatment chamber wall that suppresses the generation of minute particles, the coating film is generated by using the thermal spraying method. No consideration was given to the conditions to be met. Further, even in the above-mentioned conventional technique using yttrium fluoride, suppression of cracks, reduction of surface roughness, and reduction of porosity have been studied, but further improvement is required.

For this reason, in the conventional technique, the generated particles cause contamination of the sample to be treated, and the yield of treatment is impaired. Further, Patent Document 7 discloses a technique of spraying yttrium oxide and yttrium fluoride separately, but this also cannot sufficiently suppress the generation of fine particles.

Therefore, an object of the present invention is to provide a cover member for a plasma processing apparatus, a plasma processing apparatus, and a method for manufacturing a coating film, which reduces the generation of particles and improves the processing yield.

In order to solve the above problems, one of the cover members of the plasma processing apparatus according to the present invention, which is typical of the present invention, is arranged inside the vacuum vessel of the plasma processing apparatus and is arranged inside the processing chamber where plasma is formed. A cover member whose surface faces the plasma.
A part of the surface of the cover member is formed by a coating film on which a first material and a second material different from the first material are sprayed at the same time.
The coating film is achieved by fixing the particles of the second material to the particles of the first material in a melted state between the particles made of the first material.

Further, one of the typical methods for producing a coating film according to the present invention is a cover which is arranged inside a vacuum vessel of a plasma processing apparatus and is arranged inside a processing chamber where plasma is formed, and whose inner surface faces the plasma. It is a method of manufacturing a coating film that covers a member.
A plurality of particles of the first material and a second material different from the first material are sprayed onto the cover member by a plasma spraying method to form the coating film.
After the particles of the second material are melted and permeated between the plurality of particles of the first material, the second material is solidified and fixed to the particles of the first material. Achieved by forming a coating.

The structure of the coating film of the present invention is such that the first material and the second material are formed by a method called thermal spraying, and the particles and the dissolved substance are mixed and integrated. For this reason, it is difficult to express the structure of the coating in a way that expresses a normal physical structure. Therefore, in the present invention, there is a circumstance that it is impossible or almost impractical to directly specify an object by its structure or property.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a cover member for a plasma processing apparatus, a plasma processing apparatus, and a method for manufacturing a coating film, in which the generation of particles is reduced and the processing yield is improved.
Issues, configurations and effects other than those described above will be clarified by the following description of the embodiments.

FIG. 1 is a vertical cross-sectional view schematically showing an outline of the configuration of the plasma processing apparatus according to the embodiment of the present invention. FIG. 2 is a schematic view showing a method of forming a film of a coating film of an earth electrode arranged in the plasma processing apparatus according to the embodiment shown in FIG. FIG. 3 is a graph showing the intensity of X-ray diffraction with respect to the surface of the coating film of the ground electrode arranged in the plasma processing apparatus according to the embodiment shown in FIG. FIG. 4 is a graph showing a change in the number of foreign substances generated with a change in the average crystallite size of the coating film of the ground electrode arranged in the plasma processing apparatus according to the embodiment shown in FIG. 1.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4.
FIG. 1A is a vertical cross-sectional view schematically showing an outline of the configuration of the plasma processing apparatus according to the embodiment of the present invention, and FIG. 1B is a processing chamber of the plasma processing apparatus according to the present embodiment. It is sectional drawing which shows the part of the inner wall of the is enlarged.

The plasma processing apparatus of the present embodiment has a vacuum vessel having a cylindrical portion, a plasma forming portion arranged above or around the cylindrical portion around the vacuum vessel, and a vacuum vessel inside which is arranged below the vacuum vessel. It is equipped with a vacuum exhaust section, including a vacuum pump that exhausts the air. Inside the vacuum container, a processing chamber 7, which is a space in which plasma is formed, is arranged so as to be communicable with the vacuum exhaust unit.

Hereinafter, the plasma processing apparatus of this embodiment will be specifically described. The upper part of the processing chamber 7 is a space surrounded by an inner wall having a cylindrical shape, and constitutes a discharge chamber in which plasma 15 is generated. Inside the processing chamber 7 below the discharge chamber in which the plasma 15 is generated, a stage 6 which is a sample table on which the wafer 4 to be processed is placed and held on the upper surface is arranged.

The stage 6 of the present embodiment is a member having a cylindrical shape in which the central axis in the vertical direction is arranged at a position appropriately close to the discharge chamber, which can be regarded as concentric or concentric when viewed from above. A space is opened between the bottom surface of the processing chamber 7 in which the opening communicating with the vacuum exhaust portion is arranged and the lower surface of the stage 6, and between the upper end surface and the lower end surface in the vertical direction of the processing chamber 7. The stage 6 is held at an intermediate position. The space inside the processing chamber 7 below the stage 6 communicates with the discharge chamber through a gap between the side wall of the stage 6 and the cylindrical inner wall surface of the processing chamber 7 surrounding the side wall of the stage 6. Products generated in the upper surface of the wafer 4 and the discharge chamber during processing of the wafer 4 above the upper surface of the stage 6 and plasma and gas particles in the discharge chamber pass through such a gap and are discharged to the outside of the processing chamber 7 by the vacuum exhaust unit. Consists of the exhaust path to be exhausted.

The stage 6 of the present embodiment has a base material which is a metal member having a cylindrical shape, and is a heater arranged inside a dielectric film arranged so as to cover the upper surface of the base material (shown). () And a refrigerant flow path (not shown) arranged concentrically or spirally in multiple layers around the central axis inside the base material. Further, with the wafer 4 mounted on the upper surface of the dielectric film of the stage 6, a gas having heat transfer property such as He is supplied to the gap between the lower surface of the wafer 4 and the upper surface of the dielectric film. To. For this reason, a pipe (not shown) through which a heat-conducting gas flows is arranged inside the base material and the film made of a dielectric.

Further, the base material of the stage 6 is a high-frequency power supply 14 to which high-frequency power for forming an electric field for attracting charged particles in the plasma is supplied above the upper surface of the wafer 4 during processing of the wafer 4 by plasma. It is connected by a coaxial cable via an impedance matching device 13. Further, above the heater in the dielectric film above the base material, an electrostatic force for adsorbing and holding the wafer 4 on the upper surface of the dielectric film is generated inside the dielectric film and the wafer 4 as a direct current. The film-shaped electrodes to which power is supplied are arranged symmetrically around the central axis in each of a plurality of regions in the radial direction from the vertical central axis of the substantially circular upper surface of the wafer 4 or stage 6, and each has a different polarity. It is configured to be grantable.

A disk shape made of a dielectric such as quartz or ceramics, which is arranged above the upper surface of the stage 6 of the processing chamber 7 so as to face the upper surface of the stage 6 and constitutes the upper part of the vacuum vessel and airtightly seals the inside and outside of the processing chamber 7. The window member 3 provided is provided. Further, at a position below the window member 3 that constitutes the ceiling surface of the processing chamber 7, quartz or the like is arranged with a gap 8 from the lower surface of the window member 3 and has a plurality of through holes 9 in the central portion. A shower plate 2 having a disk shape made of a dielectric is provided.

The gap 8 is used to communicate with the processing gas supply pipe 50 and supply gas to the vacuum container, and a valve 51 that opens or closes the inside is arranged at a predetermined position on the processing gas supply pipe 50. .. The flow rate or speed of the processing gas (processing gas) supplied to the inside of the processing chamber 7 is adjusted by a gas flow rate control means (not shown) connected to one end side of the processing gas supply pipe 50, and the valve 51 After flowing into the gap 8 through the open processing gas supply pipe 50, it diffuses inside the gap 8 and is supplied from above into the processing chamber 7 through the through hole 9.

A vacuum exhaust section is located below the vacuum container. This vacuum exhaust unit is inside the processing chamber 7 via an exhaust port which is an opening for exhaust that is directly below the stage 6 on the bottom surface of the processing chamber 7 and is arranged so that the central axes in the vertical direction are substantially the same. Exhaust gas and particles. The vacuum exhaust unit includes a pressure adjusting plate 16 which is a disk-shaped valve that moves up and down above the exhaust port to increase or decrease the area of the flow path through which gas flows into the exhaust port, and a turbo molecular pump 12 which is a vacuum pump. And have. The pressure adjusting plate 16 is driven by an actuator (not shown) and can move up and down. Further, in the vacuum exhaust section, the outlet of the turbo molecular pump 12 is connected to and communicates with the dry pump 11 which is a roughing pump via an exhaust pipe, and a valve 18 is arranged on the exhaust pipe.

The pressure adjusting plate 16 of the present embodiment also serves as a valve for opening and closing the exhaust port. The vacuum vessel is provided with a pressure detector 75, which is a sensor for detecting the pressure inside the processing chamber 7, and a signal output from the pressure detector 75 is transmitted to a control unit (not shown) to obtain a pressure value. The pressure adjusting plate 16 is driven via the actuator based on the command signal that is detected and output from the control unit according to the value, thereby changing the vertical position and increasing or decreasing the area of the exhaust flow path. Will be done. Of the

valves

17 and 19 connected to the exhaust pipe 10, the valve 17 is a valve for slow exhaust for slowly exhausting the processing chamber 7 from atmospheric pressure to vacuum with the dry pump 11, and the valve 19 is , A valve for main exhaust for high-speed exhaust by the dry pump 11.

A configuration for forming an electric field or a magnetic field supplied to the processing chamber 7 for forming plasma is arranged above the cylindrical portion of the upper part of the vacuum vessel constituting the processing chamber 7 and around the side wall. That is, above the window member 3, a waveguide 21 is arranged, which is a conduit in which the microwave electric field supplied to the inside of the processing chamber 7 propagates inside, and the microwave electric field is oscillated at one end thereof. A magnetron oscillator 20 that outputs a wave is arranged.

The waveguide 21 includes a rectangular waveguide portion having a rectangular vertical cross section, an axis extending in the horizontal direction, and a magnetron oscillator 20 arranged at one end thereof, and a rectangular waveguide portion. It is provided with a circular waveguide portion connected to an end portion, having a central axis extending in the vertical direction and having a circular cross section. The lower end of the circular waveguide has a cylindrical shape with an increased diameter, and a cavity in which the electric field of a specific mode is strengthened is arranged inside, and above and around the cavity, and further in the processing chamber. A plurality of stages of solenoid coils 22 and solenoid coils 23, which are magnetic field generating means, are provided so as to surround the side periphery of 7.

The plasma etching process of the wafer 4 in such a plasma processing apparatus will be described. A vacuum transfer device (not shown) such as a robot arm arranged in the transfer chamber inside the vacuum transfer container in which the unprocessed wafer 4 is another vacuum container (not shown) connected to the side wall of the vacuum container. It is placed on the tip of the arm (not shown), transported into the processing chamber 7, delivered to the stage 6, and placed on the upper surface thereof.

When the arm of the vacuum transfer device leaves the processing chamber 7, the inside of the processing chamber 7 is sealed, and the dielectric is generated by the electrostatic force generated by applying a direct current voltage to the electrostatic adsorption electrode in the dielectric film. It is retained on the body membrane. In this state, a gas having heat transfer property such as He is supplied to the gap between the wafer 4 and the upper surface of the dielectric film constituting the upper surface of the stage 6 through a pipe arranged inside the stage 6. By supplying gas as a refrigerant adjusted to a predetermined temperature by a refrigerant temperature controller (not shown) to the refrigerant flow path inside the stage 6, heat between the temperature-controlled base material and the wafer 4 is generated. Transfer is facilitated and the temperature of the wafer 4 is adjusted to a value within the range appropriate for the start of processing.

The processing gas whose flow rate or speed is adjusted by the gas flow rate control means is supplied into the processing chamber 7 through the processing gas supply pipe 50, the gap 8 and the through hole 9, and is supplied from the exhaust port by the operation of the turbo molecular pump 12. The inside of the processing chamber 7 is exhausted, and the pressure inside the processing chamber 7 is adjusted to a value within a range suitable for processing by the balance of supply and discharge.

In this state, the electric field of the microwave oscillated from the magnetron oscillator 20 propagates inside the waveguide 21, passes through the window member 3 and the shower plate 2, and is radiated into the processing chamber 7. Further, the magnetic field generated by the solenoid coils 22 and 23 is supplied to the processing chamber 7, and electron cyclotron resonance (ECR: Electron Cyclotron Resonance) is generated by the interaction between the magnetic field and the electric field of the microwave, and the atom of the processing gas is generated. Alternatively, the molecules are excited and ionized and dissociated to generate plasma 15 inside the processing chamber 7.

When the plasma 15 is formed, high-frequency power from the high-frequency power supply 14 is supplied to the base material to form a bias potential above the upper surface of the wafer 4, and charged particles such as ions in the plasma 15 are attracted to the upper surface of the wafer 4. .. As a result, the etching process of the film layer to be processed having a plurality of film layers including the film layer to be processed and the mask layer previously formed on the upper surface of the wafer 4 is formed into the pattern shape of the mask layer. Proceed along. When it is detected by a detector (not shown) that the processing of the film layer to be processed has reached the end point, the supply of high frequency power from the high frequency power supply 14 is stopped, the plasma 15 disappears, and the processing is stopped. To.

When the control unit determines that it is not necessary to further advance the etching process of the wafer 4, high vacuum exhaust is performed. Further, after the static electricity is removed and the adsorption of the wafer 4 is released, the arm of the vacuum transfer device enters the processing chamber 7 and the processed wafer 4 is delivered, and then the wafer 4 accompanies the contraction of the arm. Is carried out to the vacuum transfer chamber outside the processing chamber 7.

By the way, the inner wall surface of such a processing chamber 7 faces the plasma 15 and is exposed to the particles. On the other hand, in order to stabilize the potential of the plasma 15 which is a dielectric, it is necessary to arrange the ground electrode 40 which faces the plasma and is in contact with the plasma in the processing chamber 7.

Therefore, in the plasma processing apparatus of the present embodiment, in order to function as an electrode for grounding, the ground electrode 40, which is a ring-shaped member, covers the lower surface of the inner wall surface of the processing chamber 7 surrounding the discharge chamber. , It is arranged above the upper surface of the stage 6 so as to surround the periphery thereof. The ground electrode 40 is connected to the chassis ground via, for example, an impedance adjusting mechanism (not shown). The ground electrode 40 includes a base material made of a conductive material and a coating film covering the surface thereof. In the present embodiment, the base material of the ground electrode 40 is a base material such as a stainless alloy or an aluminum alloy. It is composed of metal. Further, the cover member may be the ground electrode 40 or may be provided independently of the ground electrode 40.

When the surface of the base metal has no coating, such a ground electrode 40 becomes a source of corrosion and foreign matter that causes contamination of the wafer 4 by being exposed to the plasma 15. Therefore, in order to suppress contamination, the inner surface of the ground electrode 40 is covered with a coating film 42 made of a material having high plasma resistance. By covering the inner surface with the coating film 42, the ground electrode 40 can suppress damage caused by plasma while maintaining the function as an electrode via plasma. Further, the ground electrode 40 is removable from the base material 41 and can be replaced as needed.

The film 42 may be a laminated film. In this embodiment, yttrium oxide (first material) and yttrium fluoride (second material) or a material containing them is sprayed onto the surface of a base material having a surface roughness within a predetermined range by using atmospheric plasma spraying. Yttrium fluoride crystals are melted and permeated between the yttrium oxide crystals of the deposited material, recrystallized and solidified, and the yttrium oxide crystals are welded to form one piece.

On the other hand, even in the base material 41 which does not have a function as a ground, a metal member such as a stainless alloy or an aluminum alloy is used. The surface of the base material 41 is also improved in corrosion resistance to plasma such as passivation treatment, thermal spraying, PVD, and CVD in order to suppress corrosion, metal contamination, and generation of foreign substances caused by exposure to plasma 15. It has been treated to reduce wear.

In order to reduce the influence of the plasma 15 on the base material 41, a cylindrical shape made of ceramic such as yttrium oxide or quartz is formed inside the inner wall surface of the base material 41 having a cylindrical shape and between the base material 41 and the discharge chamber. Cover member (not shown) may be arranged. By arranging such a cover member between the base material 41 and the plasma 15, contact between the highly reactive particles in the plasma 15 and the base material 41 and collision of charged particles are blocked or reduced, and the base material is blocked. The wear of 41 can be suppressed.

A method of forming a film 42 on the ground electrode 40 of the present embodiment will be described with reference to FIG. As shown in FIG. 2A, while applying a high voltage 203 to the nozzle 201 facing the ground electrode 40, plasma gas 202 is flowed from the nozzle 201 to generate an arc discharge, and a thermal spray frame 204 is generated. From the material supply pipe 205 arranged near the frame generation port of the nozzle 201, yttrium oxide and yttrium fluoride or the thermal spraying material 206 containing them is introduced into the thermal spraying frame 204 together with the transport gas 207, and the thermal spraying temperature is 1152 ° C to 2425 ° C. Set to and spray. That is, yttrium oxide and yttrium fluoride are sprayed at the same time. The thermal spray material 206 contains yttrium fluoride particles in a molten or semi-molten state and yttrium oxide particles in a solid or semi-molten state. When the thermal spray material 206 is sprayed onto the ground electrode 40 made of an aluminum alloy, the solid or semi-molten yttrium oxide is adhered by the molten yttrium fluoride and cooled and solidified. As a result, as shown in FIG. 2B, which is an enlarged cross-sectional view of the ground electrode 40, a mixed film of yttrium oxide crystal 209 and yttrium fluoride crystal 210 is formed. This is repeated to form a film 42 having a thickness of about 100 μm.

The powders of yttrium oxide and yttrium fluoride, which are the thermal spray material 206, have sizes of 0.1 to 3 μm and 10 to 60 μm, respectively, and the average crystallite size is 50 nm or less by powder X-ray diffraction. Was confirmed.

The thermal spraying condition for forming the coating film 42 of the present embodiment may be any of plasma spraying, SPS thermal spraying, and reduced pressure thermal spraying, and the distance between the nozzle 201 and the ground electrode 40 and the thermal spraying speed (gas type, gas amount) may be determined. While controlling, the powdered thermal spray material 206 is supplied, and a film is formed so as to have a predetermined thickness. _{Generally, N 2} or Ar is used for the transport gas 207, but when He is used, the velocity of the thermal spray frame 204 is increased, and a more dense film can be formed. The temperature at the time of thermal spraying can be controlled by the distance between the generation port of the thermal spray frame and the material supply pipe 205 into which the thermal spray material 206 is introduced. The temperature distribution is the highest in the vicinity of the frame generation port, and the temperature becomes lower as it is closer to the base material forming the film. In advance, the particle velocity at the outlet of the nozzle 201 was measured with a sprayed particle velocity temperature measuring device (product name DPV-2000) manufactured by Tecnar, and the nozzle position was adjusted using this as the sprayed temperature. Here, the spraying temperature was set to 1300 ° C. to form a film.

In the present embodiment, the surface of a mixed powder of yttrium oxide and yttrium fluoride having an average crystallite size of 50 nm or less, or an yttrium oxide powder having an average crystallite size of 50 nm or less, respectively. The powder was fluorinated and coated with yttrium fluoride as a raw material, and sprayed at a temperature higher than the melting point of yttrium fluoride of 1152 ° C. and lower than the melting point of yttrium oxide of 2425 ° C. The particle size of the raw material powder is preferably in the range of 50 nm to 10 μm.

Masao Sato et al., " _{Production of Yttrium Iron Garnet Single Crystal in YF 3-} PBF ₂ Molten Salt Bath", Journal of the Ceramic Society, 71 [1], pp. 5 (1969) Fig. No. 1 shows that 15 mol% of yttrium oxide is dissolved in the yttrium fluoride melt at 1260 ° C. In this temperature range, the grain boundaries and low-density regions of the yttrium oxide particles dissolve in the yttrium fluoride melt, and yttrium oxyfluoride is generated during solidification. Since typical stable phase of oxyfluoride yttrium is YOF and Y ₅ O ₄ F _7, as oxyfluoride yttrium generated during solidification becomes stable phase, yttrium oxide contained in the spray material 206 and yttrium fluoride The mixing ratio of yttrium oxide powder and yttrium fluoride powder was set so that the volume ratio was in the range of 1: 1 to 4: 7.

Further, as the spraying material 205, a powder obtained by reacting yttrium oxide powder with HF gas and passing it through an aqueous solution of hydrofluoric acid to fluoride the surface of yttrium oxide powder and covering it with yttrium fluoride can also be used. .. In this case, the volume ratio of yttrium oxide and yttrium fluoride is controlled by the time for reacting with HF gas and the time for passing through the hydrofluoric acid aqueous solution, and the volume ratio of yttrium oxide and yttrium fluoride contained in the hydrofluoric acid material 205 is 1. It was adjusted to be in the range of 1: 1 to 4: 7. In addition, since the crystallite size of yttrium oxide is the size of the crystal that was not fluorinated, the average crystallite size was measured again using powder X-ray diffraction after the fluorination treatment, and it was confirmed that it was 50 nm or less. did.

When the spraying temperature is set to 1300 ° C, yttrium oxide remains solid and yttrium fluoride is sprayed as a melt. When solid yttrium oxide heated to 1300 ° C. is injected together with the yttrium fluoride melt at 1300 ° C., yttrium oxide is dissolved in the yttrium fluoride melt by about 15 mol%, so that the grain boundaries of the yttrium oxide particles are low. Yttrium fluoride melt infiltrates into the density region. The infiltrated yttrium fluoride and the melted yttrium oxide form crystals of yttrium fluoride and yttrium oxyfluoride during cooling and solidification, and the unmelted yttrium oxide crystals are adhered and solidified. Further, the yttrium oxide particles are adhered and cooled and solidified by the yttrium fluoride melt sprayed together. Even when a film is formed under normal plasma spraying conditions, yttrium fluoride and yttrium oxyfluoride tend to form microcrystals of 40 nm or less. Therefore, as shown in FIG. 2 (b), the yttrium oxide crystal 209 is formed in the coating 42. It exists isolated in the yttrium fluoride crystal 210 (yttrium oxide crystal 209 is surrounded by the yttrium fluoride crystal 210), and the boundary between the yttrium oxide crystal 209 and the yttrium fluoride crystal 210 is yttrium oxyfluoride (Fig.). It can be a film structure in which (not shown) is formed.

It is known that the film 42 formed by thermal spraying has large surface irregularities and porosity. It is considered that this is because the melt ejected at the time of thermal spraying forms air entrainment vacancies, and cracks are generated due to heat shrinkage during rapid cooling and solidification. In the present embodiment, since yttrium oxide is jetted as a melt while yttrium oxide is still solid, the melt portion where cracks are generated due to heat shrinkage when air is entrained and quenching and solidifying is limited to yttrium fluoride. Will be done. Therefore, the surface unevenness of the coating film 42 is relatively small, and the number of pores 211 is also reduced. The porosity in the volume ratio of yttrium fluoride can be reduced to about 50% of the prior art, and the surface unevenness can be reduced to about 30%. By increasing the crystal size of yttrium oxide, the surface unevenness and porosity can be further reduced. For example, Japanese Patent Application Laid-Open No. 2019-192701 (Patent Document 7), Kazuhiro Ueda et al., "Study of crystal structure and foreign matter generation mechanism of yttrium-based material for plasma etching equipment", Advances in X-ray analysis 50, pp. 197 (2019) [hereinafter referred to as Academic Document 1], Fig. 4, Fig. As shown in 5, since the generation of foreign matter increases when the average crystallite size is increased, it is preferable to limit the crystallite size of yttrium oxide to 50 nm or less. Further, since yttrium oxide is a solid, it has a higher flight speed than yttrium fluoride, which is a melt, and when it collides with the surface of a base material, it contains compressive stress inside. Furthermore, Fig. In No. 3, it is shown that yttrium oxide with less foreign matter generation has a larger compressive residual stress. That is, if the residual stress in the yttrium oxide crystal is large, the generation of foreign matter can be suppressed. Further, since yttrium oxide is present around the solidified yttrium fluoride, the specific heat of yttrium oxide is large and the thermal conductivity is low, so that the cooling rate becomes slow and the high temperature phase decreases. Yttrium fluoride having a small amount of high temperature phase produces less foreign matter as described in Japanese Patent Application Laid-Open No. 2019-192701 (Patent Document 7).

As described above, yttrium oxide crystals having an average crystallite size of 50 nm or less and yttrium fluoride having an average crystallite size of 50 nm or less, which have low surface irregularities and porosity, or a material containing them are adhered to the coating film 42 of the present embodiment. It was solidified and formed integrally.

The present inventors measured the crystallite size of the coating film 42 composed of yttrium oxide and yttrium fluoride or a material containing them by using in-plane X-ray diffraction. The X-ray incident angle was fixed at 1.5 °, and 2θ was measured from 10 ° to 100 °. FIG. 3 is a measurement example in which 2θ is in the range of 13 ° to 38 °. As shown in this figure, the coating 42 has a cubic yttrium oxide (Y ₂ O ₃ ) crystal 209, an Orthorhombic yttrium fluoride (YF ₃ ) crystal 210, and an Orthorhombic yttrium oxyfluoride (Y ₅ O ₄ F ₇ ) crystal 212. Was included. The present inventors indexed each diffraction peak to obtain the full width at half maximum, and obtained the average crystallite size of yttrium oxide, yttrium fluoride, and yttrium oxyfluoride by the Hall method. Under most film-forming conditions, the average crystallite size of yttrium fluoride and yttrium oxyfluoride was around 30 nm. The film quality was also the same as that when yttrium fluoride or yttrium oxyfluoride was formed alone.

When a film is formed under the conventional plasma spraying conditions in which yttrium oxide melts, yttrium oxide crystals grow during cooling, and the average crystallite size is 70 to 100 nm. Further, when yttrium oxide is formed at a temperature lower than the melting point, a film having a low film quality is formed. Therefore, in the prior art, yttrium oxide is melted or sprayed at 2425 ° C. or higher, which is in a semi-melted state. However, in the thermal spraying method according to the present embodiment, the low density region and the grain boundary that lower the film quality are dissolved in the yttrium fluoride melt to become yttrium oxyfluoride. In addition, each crystallite of yttrium oxide is separated by yttrium oxyfluoride or yttrium fluoride, which inhibits grain growth during cooling. As a result, the average crystallite size of yttrium oxide contained in the coating film 42 becomes equal to or smaller than the average crystallite size of the raw material powder. Here, for comparison, a film 42 having an average crystallite size of yttrium oxide of 38 nm and 70 nm was prepared.

Based on the finding in Japanese Patent Application Laid-Open No. 2019-192701 (Patent Document 7) that the generation of foreign matter decreases as the average crystallite size of the welded film material decreases, the inventors of the welding method The number of foreign substances generated was evaluated for a plurality of types of coating films 42 having different average crystallite sizes using raw material powders having different conditions and average crystallite sizes. Regarding the number of foreign substances generated, the ground electrode 40 is installed in the plasma processing device, the ceramic component (not shown) inside the base material 41 is made of quartz, and the foreign matter containing yttrium may generate the ground electrode 40. I counted it so that I could understand it. The above-mentioned etching process was repeated, and the foreign matter remaining on the wafer was analyzed by energy dispersive X-ray spectroscopy (SEM-EDX), and the foreign matter containing yttrium was counted. The result is shown in FIG. 4 with a black circle marker.

FIG. 4 is a graph showing changes in the number of foreign substances generated from the coating film with respect to different average crystallite sizes of the coating film of the ground electrode of the plasma processing apparatus according to the embodiment shown in FIG. Even if the material of the film 42 is changed to yttrium oxide, yttrium fluoride, or yttrium oxyfluoride, the correlation between the average crystallite size and the number of foreign substances generated is in a linear relationship in the Log-Log plot. It was found that the number of foreign substances generated from the coating film containing a plurality of crystals consisting of a large number of crystals depends on the large average crystallite size.

Under most of the thermal spraying conditions of the present invention, the average crystallite size of yttrium fluoride and yttrium oxyfluoride is at the level of 30 nm, so that almost no foreign matter is generated. Further, the crystallite size of yttrium oxide of the coating film 42 and the result of the foreign matter generation test according to the present embodiment are shown in FIG. In the figure, the film indicated by the white diamond marker has a large average crystallite size of yttrium oxide contained in the thermal spray material 206, the average crystallite size of yttrium oxide contained in the film-formed film is 70 nm, and yttrium fluoride is It was 30 nm. From this result, it can be seen that the amount of foreign matter generated correlates with the average crystallite size of yttrium oxide having a large average crystallite size.

Similarly, in the film indicated by the black diamond marker, the average crystallite size of yttrium oxide contained in the sprayed material 206 is small, the average crystallite size of yttrium oxide contained in the film-formed film is 38 nm, and yttrium fluoride is 28 nm. Met. As shown in FIG. 4, the number of foreign substances generated from this coating was very small. Here, it was not possible to prepare a film 42 in which the average crystallite size of yttrium oxide is smaller than the crystallite size of yttrium fluoride. From the above, it can be seen that the size of the crystallite size of the coating determines the amount of foreign matter generated. From this, according to the present embodiment, it is possible to suppress the generation of foreign matter from the coating film 42 made of a material containing yttrium oxide and yttrium fluoride.

The present invention is not limited to the above-described embodiment, and includes various modifications. The above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. For example, yttrium oxyfluoride may be used as the second material.

2 ... shower plate, 3 ... window member, 4 ... wafer, 6 ... stage, 7 ... processing chamber, 8 ... gap, 9 ... through hole, 11 ... dry pump, 12 ... turbo molecular pump, 13 ... impedance matcher, 14 High frequency power supply, 15 ... plasma, 16 ... pressure control plate, 17 ... valve, 18 ... valve, 19 ... valve, 20 ... magnetron oscillator, 21 ... waveguide, 22 ... solenoid coil, 23 ... solenoid coil, 40 ... earth Electrode (cover member), 41 ... base material, 42 ... coating, 50 ... processing gas supply pipe, 51 ... valve, 75 ... pressure detector, 201 ... nozzle, 202 ... plasma gas, 203 ... high voltage, 204 ... spraying frame , 205 ... material supply pipe, 206 ... sprayed material, 207 ... transport gas, 209 ... yttrium oxide (Y ₂ O ₃ ) crystal, 210 ... yttrium fluoride (YF ₃ ) crystal, 211 ... vacancies, 212 ... yttrium oxyfluoride. (Y ₅ O ₄ F ₇ ) Crystal

Claims

A cover member that is arranged inside the vacuum vessel of the plasma processing apparatus and is arranged inside the processing chamber where plasma is formed, and whose inner surface faces the plasma.
A part of the surface of the cover member is formed by a coating film on which a first material and a second material different from the first material are sprayed at the same time.
The coating film is a cover member of a plasma processing apparatus in which the particles of the second material are adhered to the particles of the first material in a melted state between the particles made of the first material.
The cover member of the plasma processing apparatus according to claim 1.
The coating film is a plasma formed by mixing the first material and the second material and spraying them at a spraying temperature higher than the melting point of the second material and lower than the melting point of the first material. Cover member of processing equipment.
The cover member of the plasma processing apparatus according to claim 1.
A cover member of a plasma processing apparatus in which the average value of the crystallite sizes of the first material and the second material is 50 nm or less, respectively.
The cover member of the plasma processing apparatus according to claim 1.
A cover member of a plasma processing apparatus in which the first material is yttrium oxide and the second material is yttrium fluoride or yttrium oxyfluoride.
A plasma processing apparatus provided with the cover member according to any one of claims 1 to 4.
It is a method of manufacturing a coating film which is arranged inside a vacuum vessel of a plasma processing apparatus and is arranged inside a processing chamber where plasma is formed and whose inner surface covers a cover member facing the plasma.
A plurality of particles of the first material and a second material different from the first material are mixed and sprayed onto the inner surface of the cover member by a plasma spraying method.
After the particles of the second material are melted and permeated between the plurality of particles of the first material, the second material is solidified and fixed to the particles of the first material. A method for manufacturing a coating film to form a coating film.
In the method for producing a coating film according to claim 6,
Using a mixed powder of the first material and the second material or a powder obtained by coating the surface of the powder of the first material with the second material as a raw material, spraying on the inner surface of the cover member. A method of manufacturing a coating film.
In the method for producing a coating film according to claim 6,
A method for producing a coating film in which the first material and the second material are mixed and sprayed so that the volume ratio is in the range of 1: 1 to 4: 7.
In the method for producing a coating film according to claim 6,
A method for producing a coating film in which the particle size of the first material and the raw material powder of the second material is in the range of 50 nm to 10 μm.
In the method for producing a coating film according to claim 6,
A method for producing a film in which the first material is yttrium oxide and the second material is yttrium fluoride or yttrium oxyfluoride.
In the method for producing a coating film according to claim 6,
A method for producing a coating film in which the first material and the second material are sprayed at a temperature higher than 1152 ° C and lower than 2425 ° C.
In the method for producing a coating film according to claim 6,
A method for producing a coating film in which the average value of the sizes of the crystallites constituting the coating film is 50 nm or less.