Plasma spraying slurry, method for manufacturing a sprayed film, alumina sprayed film, and sprayed member

Abstract

A slurry for plasma spraying, which contains 20 mass% or more and 80 mass% or less of alumina particles having a maximum particle diameter (D100) of 15 μm or less, with 1 or 2 or more selected from water and organic solvents as a dispersion medium, has a transmittance of 90% or less for a supernatant after 700 mL of the slurry for plasma spraying is put in a 1-L container having a height of 193 mm and left to stand at room temperature for 168 hours. By using the slurry for plasma spraying of the present application, an alumina-containing sprayed film having a low porosity, a sufficient film thickness, and a small temperature change in resistance per unit volume can be stably formed on a substrate, and a sprayed member having such a sprayed film can be used for an electrostatic chuck.

Description

TECHNICAL FIELD

[0001] The present application relates to a slurry for plasma spraying containing alumina, a method for manufacturing a sprayed film using the slurry for plasma spraying, an alumina sprayed film, and a sprayed member. BACKGROUND

[0002] Alumina has been used in a wide range of applications because it can form a film and a sintered body that are high in electrical insulation and high in hardness. For example, for an electrostatic chuck used in a semiconductor manufacturing device, as a conventional method, alumina-titanium oxide binary system ceramic sprayed material that is formed into a film by atmospheric plasma spraying is used for the electrostatic chuck (Patent Document 1: Japanese Patent Application Publication No. 2008-277862), but the porosity of the sprayed film is as high as 5% or more and 15% or less (Patent Document 2: Japanese Patent Application Publication No. 2014-156651), and the surface is porous, so the specific surface area becomes large, and depending on the use environment, it sometimes becomes a cause of deterioration due to corrosion of the dielectric layer and the like.

[0003] Recently, due to improvements in film formation techniques such as spraying, a technique capable of forming a film close to a sintered body has been developed, and in order to eliminate the above problems, film formation using an aerosol deposition method (AD method), a suspended plasma spraying method (SPS method) has been proposed.

[0004] For example, in the suspended plasma spraying method, by using particles having an average particle diameter D50 of 1 μm or more and 5 μm or less as a slurry in spraying, a rare earth oxyfluoride film having a film thickness of about 100 μm with a porosity of 1% or less can be obtained (Patent Document 3: International Publication No. 2018 / 012454).

[0005] The film thickness of this rare earth oxyfluoride film is about 100 μm, and in the case of application to an electrostatic chuck, in order to ensure insulation with respect to the voltage applied in order to adsorb a substrate, it is desirable that the film thickness be as thick as possible (Patent Document 4: Japanese Patent Application Publication No. 2007-251124), and it is desirable to have an alumina film having a film thickness exceeding 100 μm.

[0006] In addition, in the case of application to an electrostatic chuck, in order to suppress the variation in electric stress generated at the time of temperature rise in etching processing, in addition to the thickness, an alumina film that is small in temperature change of resistance is required.

[0007] PRIOR ART DOCUMENTS

[0008] PATENT DOCUMENTS

[0009] Patent Document 1: Japanese Patent Application Publication No. 2008-277862

[0010] Patent Document 2: Japanese Patent Application Publication No. 2014-156651

[0011] Patent Literature 3: International Publication No. 2018 / 012454

[0012] Patent Literature 4: Japanese Patent Application Publication No. 2007-251124 SUMMARY

[0013] PROBLEMS TO BE SOLVED BY THE INVENTION

[0014] The present application has been achieved in view of the above problems, and aims to provide a plasma spraying slurry capable of producing an alumina coating film having a low porosity, a sufficient film thickness, and a small temperature change in resistance per unit volume, a method for producing a sprayed film using the plasma spraying slurry, an alumina sprayed film, and a sprayed member.

[0015] MEANS FOR SOLVING THE PROBLEMS

[0016] To solve the problems, the present inventors have conducted intensive studies, and as a result, have found that a sprayed member provided with an alumina sprayed film on a substrate obtained using a spraying slurry containing 20% by mass or more and 80% by mass or less of alumina particles having a maximum particle diameter (D100) of 15 μm or less, with one or two or more selected from water and an organic solvent as a dispersion medium, and having a transmittance of 90% or less of a supernatant liquid when 700 mL of the spraying slurry is put in a 1-L container having a height of 193 mm, and the supernatant liquid is collected after being left to stand at room temperature for 168 hours, is excellent in performance, thereby completing the present application.

[0017] Therefore, the present application provides the following plasma spraying slurry, method for producing a sprayed film, alumina sprayed film, and sprayed member.

[0018] 1. A plasma spraying slurry, characterized by containing 20% by mass or more and 80% by mass or less of alumina particles having a maximum particle diameter (D100) of 15 μm or less, with one or two or more selected from water and an organic solvent as a dispersion medium, and having a transmittance of 90% or less of a supernatant liquid when 700 mL of the plasma spraying slurry is put in a 1-L container having a height of 193 mm, and the supernatant liquid is collected after being left to stand at room temperature for 168 hours.

[0019] 2. The plasma spraying slurry according to 1, characterized in that the alumina particles have an average particle diameter D50 of 2 μm or more and 8 μm or less, a crystallite size of 350 nm or more and 600 nm or less, and a crystal structure of α-alumina.

[0020] 3. The plasma spraying slurry according to 1 or 2, characterized in that it further contains 3% by mass or less of one or more particulate additives selected from rare earth oxides, alumina and titanium oxide, wherein the average particle size D50 of the particulate additives is 0.3 μm or less.

[0021] 4. The plasma spraying slurry according to claim 3, characterized in that the rare earth element is one or more selected from yttrium (Y), gadolinium (Gd), holmium (Ho), erbium (Er), ytterbium (Yb), and lutetium (Lu).

[0022] 5. A method for manufacturing a plasma-sprayed film, characterized in that a plasma-sprayed slurry according to any one of 1 to 4 is used.

[0023] 6. The method for manufacturing the spray-coated film according to 5, characterized in that an atmospheric spray coating method is used.

[0024] 7. An alumina spray-coated film, characterized in that the porosity is less than 1%, the film thickness is more than 100 μm, and the value of the temperature variable expressed as (volume resistivity at 23°C) / (volume resistivity at 200°C) is more than 1 and less than 20.

[0025] 8. A spray-plated component, characterized in that it comprises a spray-plated film obtained by the manufacturing method according to 5 or a spray-plated film according to 7.

[0026] 9. The spray-plating component according to 8, characterized in that it is an electrostatic chuck.

[0027] The effects of the invention

[0028] By using the plasma spraying slurry of the present invention, a sprayed film containing alumina with low porosity, sufficient film thickness, and small temperature change in resistance per unit volume can be stably formed on a substrate. A sprayed component having such a sprayed film can be used in an electrostatic chuck. Attached Figure Description

[0029] Figure 1 The image shows the X-ray diffraction pattern of the alumina particles in Example 1.

[0030] Figure 2 The image shows the X-ray diffraction pattern of the sprayed film in Example 1.

[0031] Figure 3 This represents the distribution of grayscale values ​​in a cross-sectional image of the sprayed film. Detailed Implementation

[0032] The present invention will now be described in more detail.

[0033] In the present application, the alumina particles are deposited as a slurry. The slurry of the present application contains alumina particles. The maximum particle diameter (D100 (D100 in the present application is the maximum particle diameter in the particle diameter distribution on a volume basis.)) of the alumina particles is preferably 15 μm or less, more preferably 12 μm or less. If the D100 exceeds 15 μm, it is likely that clogging occurs between the slurry supply device and the deposition gun. The slurry of the present application preferably contains no particles having a particle diameter exceeding 15 μm. The content of the alumina particles in the slurry of the present application is preferably 20% by mass or more, more preferably 25% by mass or more, further preferably 30% by mass or more, and is preferably 80% by mass or less, more preferably 60% by mass or less, further preferably 50% by mass or less.

[0034] The average particle diameter D50 (D50 in the present application is the cumulative 50% diameter (median diameter) in the particle diameter distribution on a volume basis) of the alumina particles is preferably 2 μm or more, particularly preferably 3 μm or more, and is preferably 8 μm or less, particularly preferably 5 μm or less.

[0035] The specific surface area (BET specific surface area) of the alumina particles is preferably 3 m 2 / g or less, particularly preferably 1 m 2 / g or less. The lower limit of the specific surface area (BET specific surface area) of the alumina particles is not particularly limited, and is preferably 0.1 m 2 / g or more.

[0036] The crystal structure of the alumina particles contained in the slurry of the present application is preferably α-type. Of the crystal phases of alumina, there are α-type, η-type, κ-type, δ-type, χ-type, γ-type, θ-type, and the like, and the high-temperature α-type is preferred because of its good stability in the slurry.

[0037] In addition, the crystallite size of the alumina particles, which is obtained by the WPPD method (Whole Powder Pattern Decomposition method) using X-ray diffraction in the range of 2θ = 10° to 70°, is preferably 350 nm or more, more preferably 400 nm or more, and is preferably 600 nm or less, more preferably 500 nm or less.

[0038] With respect to the settling of the particles contained in the slurry, the transmittance of the supernatant after the slurry is left to stand at room temperature for 168 hours is preferably 90% or less, more preferably 80% or less, in a container having a volume of 1 L, such as a polypropylene container, having a height of 193 mm.

[0039] The slurry of the present application contains a large amount of fine deposition particles, and as a result, although not particularly limited, it is presumed that a deposition film which is thick and dense can be stably produced.

[0040] As the dispersion medium of the slurry, one or two or more selected from water and an organic solvent is used. The dispersion medium can be water alone, a mixture of water and an organic solvent, or an organic solvent alone. As the organic solvent, one that is selected in consideration of harmfulness and environmental impact is preferable, and, for example, alcohols, ethers, esters, ketones, and the like can be mentioned. More specifically, monohydric or dihydric alcohols having a carbon number of 2 to 6, ethers having a carbon number of 3 to 8 such as ethyl cellosolve, diethylene glycol dimethyl ether (DMDG), glycol ethers having a carbon number of 4 to 8 such as ethyl cellosolve acetate, glycol esters having a carbon number of 4 to 8 such as butyl cellosolve acetate, cyclic ketones having a carbon number of 6 to 9 such as isophorone, and the like are preferable. Among the organic solvents, from the viewpoint of flammability and safety, water-soluble organic solvents that can be mixed with water are particularly preferable.

[0041] The slurry of the present application can contain a particulate additive selected from one or two or more of rare earth oxides, aluminum oxides (preferably, α-type aluminum oxide), and titanium oxides. The average particle diameter (D50 (volume basis)) of the particulate additive is preferably 0.3 μm or less, more preferably 0.2 μm or less. The content of the particulate additive in the slurry is preferably 3% by mass or less, particularly preferably 1% by mass or less, preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more.

[0042] In the present application, as the rare earth element, one or two or more selected from yttrium (Y), gadolinium (Gd), holmium (Ho), erbium (Er), ytterbium (Yb), and lutetium (Lu) is preferable. More preferably, the rare earth element contains any one of yttrium, gadolinium, ytterbium, and lutetium, and particularly preferably, the rare earth element contains only yttrium, or is composed of yttrium as a main component (for example, 90% by mole or more) and the balance of ytterbium or lutetium.

[0043] The specific surface area (BET specific surface area) of the particulate additive is preferably 80 m 2 / g or less, more preferably 60 m 2 / g or less. The lower limit of the specific surface area (BET specific surface area) of the particulate additive is not particularly limited, and is preferably 1 m 2 / g or more.

[0044] To prevent aggregation of the alumina particles, the slurry of the present application can contain an anti-aggregation agent composed of an organic compound, particularly a water-soluble organic compound. As the anti-aggregation agent, a surfactant or the like is preferred. Since alumina has a + charge due to the zeta potential, an anionic surfactant is preferred, and particularly preferably an anionic surfactant of the polyethyleneimine type, an anionic surfactant of the polycarboxylic acid type, or the like is used. In the case where the dispersion medium contains water, an anionic surfactant is preferred, and in the case where the dispersion medium is only an organic solvent, a nonionic surfactant can also be used. The content of the anti-aggregation agent in the slurry is preferably 3% by mass or less, particularly preferably 1% by mass or less, and preferably 0.01% by mass or more, particularly preferably 0.03% by mass or more.

[0045] The slurry of the present application can be produced by mixing a prescribed amount of alumina particles and a dispersion medium, and other components such as an anti-aggregation agent, a particle additive, or the like, as necessary. In particular, in order not to excessively pulverize the solid components such as alumina particles, for example, it is preferred to use a resin-made ball mill and resin-made balls (for example, 5 mmφ) (see the above). In this case, the mixing time can be set to 1 hour or more and 6 hours or less, for example. Furthermore, in order to break up aggregated particles and remove inclusions, it is effective to pass the mixed slurry through a sieve of 500 mesh (mesh size 25 μm) or less.

[0046] The slurry of the present application is preferably used for plasma spraying in an atmosphere containing an oxygen-containing gas, particularly atmospheric suspension plasma spraying in which a plasma is formed in an atmospheric gas. In the present application, the case where the gas of the atmosphere around where the plasma is formed is atmospheric air is referred to as atmospheric suspension plasma spraying. In addition, the pressure of the place where the plasma is formed can be under pressure, under reduced pressure, in addition to normal pressure under atmospheric pressure. Furthermore, it can be HVOF spraying.

[0047] As the substrate, stainless steel, aluminum, nickel, chromium, zinc, and alloys thereof, alumina, aluminum nitride, silicon nitride, silicon carbide, quartz glass, and the like are selected, and are appropriately selected in accordance with the use of the sprayed member.

[0048] The plasma gas used for forming the plasma is preferably a mixed gas composed of 2 or more kinds selected from argon, hydrogen, helium, and nitrogen, particularly preferably a mixed gas of 2 kinds of argon and nitrogen, a mixed gas of 3 kinds of argon, hydrogen, and nitrogen, or a mixed gas of 4 kinds of argon, hydrogen, helium, and nitrogen.

[0049] As the spraying operation, specifically, for example, first, the slurry containing alumina particles is filled into a slurry supply device, and using a pipe (powder hose), the slurry of the present application is supplied to the tip end portion of a plasma spraying gun using a carrier gas (typically argon).

[0050] The inner diameter of the pipe is preferably 0.5 mm or more and 5 mm or less.​ By providing a sieve of 500 mesh (25 μm mesh size) or less, preferably about 100 mesh (149 μm mesh size) in any of the pipes, for example, to the slurry supply port of the pipe, it is possible to prevent clogging in the pipe or the plasma spraying gun.

[0051] The sprayed film can be formed by using an automatic device (robot) or a person's hand (manual) to scan a prescribed range on the surface of the substrate while moving the liquefied frame to the left and right or up and down along the surface of the substrate. The thickness of the sprayed film is preferably 100 μm or more, more preferably 150 μm or more. In addition, it is preferably 300 μm or less, more preferably 250 μm or less.

[0052] There are no particular restrictions on the spraying conditions such as the spraying distance, current value, voltage value, gas type, and gas supply amount in the suspended plasma spraying, and the conditions known in the art can be applied, and can be appropriately set according to the substrate, the slurry containing alumina particles, the use of the resulting sprayed member, and the like. In addition, a layer of rare earth oxide, rare earth fluoride, rare earth oxyfluoride, or the like having a thickness of about 50 μm to 300 μm can be formed on the substrate in advance as a base film by, for example, atmospheric plasma spraying under normal pressure, atmospheric suspended plasma spraying, or the like, and the sprayed film of the present application can be formed thereon.

[0053] The sprayed film of the present application is an oxide sprayed film, and the oxide is an oxide composed of alumina when the slurry contains only alumina, and is an oxide containing alumina as a main component and a small amount of components from the particulate additive (oxides of rare earth elements, titanium, and the like, composite oxides, and the like) when the slurry contains a rare earth oxide, a titanium oxide, or the like as a particulate additive. In the present application, the oxide constituting the alumina sprayed film contains both the oxide composed of alumina and the oxide containing alumina as a main component and a small amount of components from the particulate additive. The porosity of the alumina sprayed film of the present application is 1% or less, the temperature dependence of the volume resistivity obtained by dividing the volume resistivity at 23°C by the volume resistivity at 200°C is 1 or more and 20 or less, and the temperature dependence of the volume resistivity is low, and the alumina sprayed film can be used for an electrostatic chuck.

[0054] When the sprayed member provided with the sprayed film of the present application is used as an electrostatic chuck, sufficient electrostatic adsorption force can be obtained by reducing the surface roughness. In the case where the electrostatic adsorption force cannot be obtained due to a large surface roughness, a method of polishing the surface of the sprayed film is also effective. In order to easily polish the surface, the surface roughness is preferably small, and the surface roughness Ra is preferably 3.5 μm or less.

[0055] It is known that ceramics of alumina are high in hardness and excellent in wear resistance. The sprayed film of alumina is also similarly preferably high in hardness, and the Vickers hardness is preferably 700 HV or more.

[0056] Examples

[0057] The following shows examples and comparative examples to specifically explain the present application, but the present application is not limited by the examples described below.

[0058] [Examples 1 to 4, Comparative Example 1]

[0059] [Manufacture of the slurry for spraying of Examples 1 to 4, Comparative Example 1]

[0060] For Examples 1 to 4, alumina particles (alumina particles of α type), a fine particle additive and an anti-agglomerating agent (a surfactant) were weighed in the proportions shown in Table 1, and a dispersion medium was prepared so as to have the contents shown in Table 1, and they were put into a nylon tank equipped with a nylon ball, mixed for about 6 hours, and the resulting mixture was passed through a sieve having a mesh size of 500 mesh (25 μm) to obtain a slurry containing alumina particles. The slurry for spraying of Comparative Example 1 was manufactured in the same manner as in Example 1 except that the D50, D100, BET specific surface area, crystallite size of the alumina particles used were different and no fine particle additive was used.

[0061] [Manufacture of the sprayed film (spraying member) of Examples 1 to 4, Comparative Example 1]

[0062] The sprayed film (spraying member) was manufactured under the spraying conditions shown in Table 2 after roughening treatment of one side of the substrate using a corundum abrasive material (#60) after degreasing of the surface of a 100 mm square (5 mm thick) A5052 aluminum alloy substrate with acetone.

[0063] [Evaluation of the slurry for spraying]

[0064] The results of the evaluation of the slurry for spraying are shown in Table 1.

[0065] (Measurement of particle size)

[0066] As for the values of D100 and D50 of the alumina particles and D50 of the fine particle additive used in the slurry for spraying of Examples 1 to 4, Comparative Example 1, the slurry was prepared by putting the alumina particles and the fine particle additive into pure water, and after ultrasonic treatment of the prepared slurry for 1 minute at 40 W, the particle size distribution measuring device MT-3300 manufactured by Microtrack Corporation was used to measure the values by the laser diffraction method.

[0067] (Measurement of BET specific surface area)

[0068] ​The specific surface area of the alumina particles and the particulate additive used in the slurries for sputtering of Examples 1 to 4 and Comparative Example 1 was measured using a Macsorb HM model-1280 manufactured by the company Mountech.

[0069] (X-ray diffraction measurement and measurement of crystallite size)

[0070] The X-ray diffraction of the alumina particles used in the slurries for sputtering of Examples 1 to 4 and Comparative Example 1 was measured using an X-ray diffractometer (X-Part Pro MPD, CuKα ray, manufactured by PANalytical). α In addition, the crystallite size was calculated from the obtained X-ray diffraction measurement results using the WPPD method (Whole Powder Pattern Decomposition method) in the range of 2θ = 10° to 70°. The measurement results of the X-ray diffraction of the alumina particles of Example 1 are shown in Table 1. Figure 1

[0071] (Measurement of turbidity and transmittance)

[0072] After the slurries for sputtering of Examples 1 to 4 and Comparative Example 1 were stirred and dispersed until they became uniform, 700 mL of the slurry was filled in a 1L container (JK-PP jar 1000 mL, manufactured by Kenis Corporation) having a height of 193 mm, and left to stand for 168 hours. Then, the turbidity of the supernatant was measured at the middle between the bottom surface of the container and the liquid surface of the slurry. The turbidity was measured using a digital turbidimeter TBD700 manufactured by Aswan Corporation.

[0073] On the other hand, in order to measure the transmittance, after being left to stand for 168 hours as in the measurement of the turbidity, the supernatant was collected in a quartz cell from the middle between the bottom surface of the container and the liquid surface of the slurry. The transmittance was measured using a spectrophotometer (LAMBDA 750 (light source D2 tungsten), manufactured by PerkinElmer) in the wavelength range of 250 nm to 850 nm, the data interval was set to 1 nm, and the scanning speed was set to 256.75 nm / min. The transmittance at a wavelength of 550 nm was read from the results.

[0074] [Evaluation of sputtered film]

[0075] The evaluation results of the sputtered film are shown in Table 3.

[0076] (X-ray diffraction measurement)

[0077] The sputtered film was cut out from the obtained sputtered member, and analyzed using an X-ray diffraction method. In the X-ray diffraction, an X-ray diffractometer (X-Part Pro MPD, CuKα ray, manufactured by PANalytical) was used.​α The X-ray diffraction measurement results of the sputtered film of Example 1 are shown in Table 1. Figure 2 The X-ray diffraction measurement results of the sputtered film of Example 1 are shown in Table 1.

[0078] (Measurement of film thickness of sputtered film)

[0079] The film thickness of the obtained coating film was measured using an eddy current film thickness meter (Kett Corporation, Model LH-300).

[0080] (Measurement of surface roughness Ra of sputtered film)

[0081] The surface roughness Ra of the obtained sputtered film was measured using a surface roughness meter, HANDYSURF E-35A, manufactured by Tokyo Denshoku Co., Ltd.

[0082] (Measurement of Vickers hardness of sputtered film)

[0083] As for the hardness of the sputtered film surface, a micro Vickers hardness tester, HMV-G31-XY-S, manufactured by Shimadzu Corporation, was used, and the measurement was performed under the measurement conditions HV0.1 (980.7 mN) for 10 seconds, 10 times each, and the average value thereof was taken as the measurement value.

[0084] (Measurement of porosity of sputtered film)

[0085] The test piece of the sputtering member was embedded in a resin, and a cross section was cut out, and after mirror finishing (Ra = 0.1 μm) of the cross section, a cross-sectional image (magnification: 200 times) was taken using a scanning electron microscope (SEM). After taking 10 fields of view (photographing area of 1 field of view: 0.017 mm 2 ) were taken, image processing was performed using an image processing software, "Photoshop" (manufactured by Adobe Systems Incorporated), and using an image analysis software, "Scion Image" (Scion Corporation), quantification of the porosity was performed, and the porosity was evaluated as a percentage with respect to the total area of the image, averaged over 10 fields of view.

[0086] The cross-sectional image taken using the electron microscope was a reflected electron image, and was expressed using 8-bit gradation. For each pixel of the cross-sectional image, the intensity of light (gradation value) was expressed using 256 gradations from 0 (state of complete absence of light: black) to 255 (state of maximum appearance of all light). In the cross-sectional image of the sputtered film, the void portion was in a state closer to black with respect to the entire sputtered film, and the gradation value was relatively low. The distribution of the gradation value of the cross-sectional image of the sputtered film is shown in Figure 3 .

[0087] For the cross-sectional image of the sputtered film, a threshold value was determined, and binarization processing was performed. The gray scale value of the gap portion was changed to 0, and the gray scale value of the entire sputtered film other than the gap portion was changed to 255. The proportion of the total number of pixels of the gap portion with respect to the total number of pixels of the cross-sectional image was defined as the porosity.

[0088] In the case where the threshold value is fixed in the binarization processing, since the brightness and contrast of each image are different, it is difficult to appropriately segment the gap. Therefore, it is necessary to determine the threshold value depending on the brightness and contrast. In a general image binarization method, a valley appearing in the distribution of the gray scale value is focused on to determine the threshold value to perform binarization, but this case is premised on bimodality of the distribution of the gray scale value. However, as shown in FIG. 6, the distribution of the gray scale value of the sputtered film is unimodal, and therefore the general image binarization method cannot be applied. Figure 3

[0089] In the present application, in order to quantitatively determine the brightness and contrast, the distribution of the gray scale value was approximated by a normal distribution shown in the following equation. x represents the gray scale value, y represents the number of pixels, a represents the maximum value of the normal distribution, b represents the gray scale value at which the maximum value is taken, and c represents the width of the normal distribution. The nonlinear least squares method was used to perform fitting such that the gray scale value x changes from 0 to 255, and the fitting parameters a, b, and c were numerically analyzed such that the sum of the squares of the residuals of the number of pixels y at that time becomes the minimum using the iterative method. As initial values, a was set to 10000, b was set to 100, and c was set to 10. In addition, as initial conditions, a was set to 0 or more, b was set to 0 or more and 255 or less, and c was set to 0 or more.

[0090] [Equation 1]

[0091]

[0092] The threshold value t was defined using the fitting parameters b and c of the normal distribution according to the following equation. The equation is a floor function, and the integer part is set as the threshold value. b corresponds to the brightness, and c corresponds to the contrast, and therefore the threshold value is determined depending on the brightness and contrast. In the case of evaluating the sputtered film of aluminum oxide, m was set to 5.35, and n was set to -62.9.

[0093] [Equation 2]

[0094]

[0095] (Measurement of volume-specific resistivity of sputtered film)

[0096] ​The volume resistivity was calculated based on the film thickness data, using a digital ultra-high resistance / micro-ammeter 8340A (manufactured by A&D Company, Limited) in accordance with the test standard ASTM (D257: 2007) to measure the volume resistances at room temperature 23°C and 200°C. Further, the "temperature variation" in Table 3 is a value calculated from (volume resistivity at 23°C) / (volume resistivity at 200°C), and the closer the temperature variation is to 1, the smaller the temperature variation in the volume resistivity.

[0097] The crystallite size of the alumina particles of Example 1 was 455 nm, which was calculated using the WPPD method (Whole Powder Pattern Decomposition method) from the obtained X-ray diffraction results. The crystallite sizes of the alumina particles of Examples 2 to 4 were 430 nm, 460 nm, and 420 nm, respectively, which were calculated using the same method. On the other hand, the crystallite size of the alumina particles of Comparative Example 1 was 250 nm, which was calculated using the same method.

[0098] A sputtering slurry of Example 1 and 2, which used water as the dispersion medium, contained alumina particles having a D100 of 15 μm or less and a crystallite size of 455 nm and 430 nm, respectively, at a content rate of 30 mass% and 50 mass% with respect to the total amount of the sputtering slurry, and further contained alumina fine particles having a D50 of 150 nm as a fine particle additive at a content rate of 0.1 mass% and 0.3 mass%, respectively, was placed in a polypropylene container having a volume of 1 L and a height of 193 mm at 700 mL and left to stand at room temperature for 168 hours, and the transmittance of the supernatant was 46.1% and 75.7%, respectively. Suspension sputtering was performed, and as a result, the film thickness was 153 μm and 213 μm, respectively, the surface roughness was 2.88 μm and 2.82 μm, respectively, the porosity was 0.42% and 0.32%, respectively, and the ratio of the resistance per unit volume at 23°C / 200°C (temperature variation) was 8.0 and 1.3, respectively.

[0099] A sputtering slurry of Example 3, which used IPA (isopropyl alcohol) as the dispersion medium, contained alumina particles having a D100 of 15 μm or less and a crystallite size of 460 nm at a content rate of 30 mass% with respect to the total amount of the sputtering slurry, and further contained Y2O3 fine particles having a D50 of 20 nm as a fine particle additive at a content rate of 0.3 mass%, was placed in a polypropylene container having a volume of 1 L and a height of 193 mm at 700 mL and left to stand at room temperature for 168 hours, and the transmittance of the supernatant was 62.3%. Suspension sputtering was performed, and as a result, the film thickness was 200 μm, the surface roughness was 3.07 μm, the porosity was 0.96%, and the ratio of the resistance per unit volume at 23°C / 200°C (temperature variation) was 3.2.

[0100] Example 4 of the present application, which used a slurry for sputtering having water as a dispersion medium, alumina particles having a D100 of 15 μm or less, a crystallite size of 420 nm, a content of 30 mass% relative to the total amount of the slurry for sputtering, and further 0.3 mass% of TiO2 fine particles having a D50 of 50 nm as fine particle additives, 0.1 mass% of polyethyleneimine as a surfactant, and a transmittance of 75.5% for the supernatant after 700 mL was put in a polypropylene container having a volume of 1 L with a height of 193 mm and left to stand at room temperature for 168 hours, was subjected to suspension sputtering, and as a result, a film having a thickness of 176 μm, a surface roughness of 2.93 μm, a porosity of 0.69%, and a ratio (temperature variation) of the resistance per unit volume at 23°C / 200°C of 1.9 was obtained.

[0101] On the other hand, Comparative Example 1 of the present application, which used a slurry for sputtering having water as a dispersion medium, alumina particles having a D100 of 18.5 μm, a crystallite size of 250 nm, a content of 30 mass% relative to the total amount of the slurry for sputtering, and a transmittance of 97.4% for the supernatant after 700 mL was put in a polypropylene container having a volume of 1 L with a height of 193 mm and left to stand at room temperature for 168 hours, was subjected to suspension sputtering, and as a result, only a film having a thickness of 87 nm, which was thinner than the film thickness of the Examples, was obtained. In addition, the surface roughness was 3.83 μm, which was larger than that of Examples 1 to 4. Further, the porosity was 1.5%, which was larger than that of Examples 1 to 4, and the porosity exceeded 1. The ratio (temperature variation) of the resistance per unit volume at 23°C / 200°C was 28.5, which was three times or more higher than that of Examples 1 to 4.

[0102] [Table 1]

[0103]

[0104] * Registered trademark (polyethyleneimine)

[0105] [Table 2]

[0106]

[0107] [Table 3]

[0108]

Claims

1. A slurry for plasma spraying, characterized by, The transmittance of supernatant after 700 mL of the plasma spraying slurry containing 20 mass% or more and 50 mass% or less of alumina particles having a maximum particle diameter D100 of 12 μm or less and 1 kind or 2 or more kinds selected from water and an organic solvent as a dispersion medium is left to stand at room temperature for 168 hours is 90% or less, The average particle diameter D50 of the alumina particles is 2 μm or more and 8 μm or less, and the BET specific surface area of the alumina particles is 3 m 2 / g or less.

2. The slurry for plasma spraying according to claim 1, wherein The average particle diameter D50 of the alumina particles is 2 μm or more and 5 μm or less, and the crystallite size is 350 nm or more and 600 nm or less, and the alumina particles have a crystal structure of α-alumina.

3. The slurry for plasma spraying according to claim 1 or 2, characterized by, The micro-particle additive is 3 mass% or less of 1 kind or 2 or more kinds selected from rare earth oxides, alumina, and titanium oxide, and the average particle diameter D50 of the micro-particle additive is 0.3 μm or less.

4. The slurry for plasma spraying according to claim 3, wherein The rare earth element is 1 kind or 2 or more kinds selected from yttrium (Y), gadolinium (Gd), holmium (Ho), erbium (Er), ytterbium (Yb), and lutetium (Lu).

5. A method for manufacturing a sputtered film, characterized by, The plasma spraying slurry according to any one of claims 1 to 4 is used.

6. The method of manufacturing a sputtered film according to claim 5, wherein The atmospheric plasma spraying method is used.

7. An aluminum oxide sputter-deposited film, characterized by, The porosity is 1% or less, the film thickness is 100 μm or more, and the value of temperature variation represented by (volume resistivity at 23°C) / (volume resistivity at 200°C) is 1 or more and 20 or less.

8. A sputter member, characterized by The sprayed film obtained by the production method according to claim 5 or the sprayed film according to claim 7 is provided.

9. The sputter member according to claim 8, characterized in that It is an electrostatic chuck.

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