PLASMA-RESISTANT COATING FILM, SOL GEL LIQUID FOR FORMING SAID FILM, METHOD FOR FORMING PLASMA-RESISTANT COATING FILM, AND SUBSTRATE WITH PLASMA-RESISTANT COATING FILM

Abstract

The plasma-resistant coating film according to the present invention is formed on a substrate, including crystalline Y.sub.2O.sub.3 particles having an average particle diameter of 0.5 μm to 5.0 μm in a SiO.sub.2 film, in which a film density of the plasma-resistant coating film is 90% or more, the film density being obtained by performing image analysis of a cross section of the film with an electron scanning microscope and by using the following expression (1), a size of pores in the film is 5 μm or less in terms of diameter, and a peeling rate of the film from the substrate measured by performing a cross-cut test is 5% or less. Film density (%)=[(S.sub.1−S.sub.2)/S.sub.1]×100 (1). However, in the expression (1), S.sub.1 is an area of the film and S.sub.2 is an area of a pore portion in the film.

Claims

1. A plasma-resistant coating film formed on a substrate, comprising: crystalline Y.sub.2O.sub.3 particles having an average particle diameter of 0.5 μm to 5.0 μm in a SiO.sub.2 film, wherein a film density of the plasma-resistant coating film is 90% or more, the film density being obtained by performing image analysis of a cross section of the film with an electron scanning microscope and by using the following expression (1), a size of pores in the film is 5 μm or less in terms of diameter, and a peeling rate of the film from the substrate measured by performing a cross-cut test is 5% or less,
Film density (%)=[(S.sub.1−S.sub.2)/S.sub.1]×100  (1) provided that, in the expression (1), S.sub.1 is an area of the film and S.sub.2 is an area of a pore portion in the film.

2. The plasma-resistant coating film according to claim 1, wherein an atomic concentration ratio (Y/Si) of yttrium (Y) to silicon (Si) in the plasma-resistant coating film obtained by performing EDS analysis is 4 to 7.

3. The plasma-resistant coating film according to claim 1, wherein an average film thickness of the plasma-resistant coating film is 10 μm to 300 μm.

4. The plasma-resistant coating film according to claim 1, wherein a main peak for a Y.sub.2O.sub.3 crystal in X-ray diffraction of the film appears in a range of 2θ=29 degrees to 29.5 degrees, and a half width of the main peak is 0.14 degrees to 0.25 degrees.

5. The plasma-resistant coating film according to claim 1, wherein the substrate is one of the group consisting of aluminum, alumina, silicon, and silicon oxide.

6. A sol gel liquid for forming a plasma-resistant coating film, which is obtained by uniformly dispersing a plurality of crystalline Y.sub.2O.sub.3 particles having an average particle diameter of 0.5 μm to 5.0 μm in a silica sol gel liquid at a proportion of 0.1 g/mL to 2.5 g/mL.

7. A method for forming a plasma-resistant coating film, comprising: coating and drying the sol gel liquid for forming a plasma-resistant coating film according to claim 6 onto a substrate; and subjecting the plasma-resistant coating film to a heat treatment at a temperature of 250° C. to 400° C. under an air atmosphere, wherein a procedure from the application of the sol gel liquid to the heat treatment is performed once or repeated multiple times.

8. The method for forming a plasma-resistant coating film according to claim 7, wherein the substrate is one of the group consisting of aluminum, alumina, silicon, and silicon oxide.

9. A substrate with a plasma-resistant coating film, comprising: a substrate; and the plasma-resistant coating film according to claim 1, which is formed on a surface of the substrate.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0027] FIG. 1 is an enlarged schematic cross-sectional view of a plasma-resistant coating film according to the present embodiment, which is formed on a substrate.

[0028] FIG. 2 is a flowchart for forming the plasma-resistant coating film according to the present embodiment.

DESCRIPTION OF EMBODIMENTS

[0029] Next, embodiments for implementing the present invention will be described with reference to the drawings.

[0030] [Method for Producing Sol Gel Liquid for Forming Plasma-Resistant Coating Film]

[0031] A sol gel liquid for forming a plasma-resistant coating film is generally produced by the following method. As shown in FIG. 2, Y.sub.2O.sub.3 particles 11 are prepared. On the other hand, a silica sol gel liquid 16 is prepared by mixing a silicon alkoxide 12 and an alcohol 13, and adding a catalyst 14 and an additive 15 to the mixed solution. By mixing the silica sol gel liquid 16 and the above-described Y.sub.2O.sub.3 particles 11, a sol gel liquid 17 for forming a plasma-resistant coating film is produced. Each step will be described in detail below.

[0032] [Preparation of Y.sub.2O.sub.3 Particles]

[0033] As the Y.sub.2O.sub.3 particles, crystalline Y.sub.2O.sub.3 particles are prepared. Commercially available crystalline Y.sub.2O.sub.3 particles can be used as the crystalline Y.sub.2O.sub.3 particles. Examples thereof include commercially available products manufactured by NIPPON YTTRIUM CO., LTD. and commercially available products manufactured by Shin-Etsu Chemical Co., Ltd. The Y.sub.2O.sub.3 particles have an average particle diameter of 0.5 μm to 5.0 μm, preferably 1 μm to 3 μm. In a case where the average particle diameter is less than 0.5 μm, the Y.sub.2O.sub.3 particles contained in the SiO.sub.2 film are likely to be etched when irradiated with plasma. In a case of being more than 5.0 μm, when the sol gel liquid for forming a plasma-resistant coating film is used for forming a film on a substrate, which will be described later, it is easy to become a crack origin of the formed plasma-resistant coating film. In order to increase arrangement density of the Y.sub.2O.sub.3 particles in the plasma-resistant coating film, the Y.sub.2O.sub.3 particles may be composed of first particles having an average particle diameter of 0.5 μm to 2 μm and second particles having an average particle diameter of 3 μm to 5 μm. As a result, by coating, the small-diameter first particles are placed in voids between the large-diameter second particles, so that the Y.sub.2O.sub.3 particles can be arranged on the substrate at a higher density, which is preferable. The mass ratio (second particles/first particles) of the second particles to the first particles is preferably 1 to 5. In the present specification, the average particle diameter of the Y.sub.2O.sub.3 particles refers to the average value (D50: median diameter) of particle diameters measured by a laser diffraction and scattering method using MT3000 manufactured by Microtrac Retsch GmbH.

[0034] [Preparation of Silica Sol Gel Liquid]

[0035] First, a mixed solution is prepared by mixing silicon alkoxide and an alcohol having a boiling point of lower than 150° C. and having 1 to 4 carbon atoms. In this case, an epoxy group-containing silane as an alkylene group-component in order to enhance bonding strength between the SiO.sub.2 film formed of the silica sol gel liquid and the substrate, formamide in order to increase a film thickness, or the like may be mixed together as an additive. Specific examples of the silicon alkoxide include tetramethoxysilane (TMOS) or an oligomer thereof, and tetraethoxysilane (TEOS) or an oligomer thereof. For example, for the purpose of obtaining a highly durable plasma-resistant coating film, tetraethoxysilane is preferably used.

[0036] Examples of the alcohol having a boiling point of lower than 150° C. and having 1 to 4 carbon atoms include alcohols such as methanol, ethanol, isopropanol, and 1-butanol. 1-butanol is particularly preferable. This is because 1-butanol has moderate volatility which is difficult to volatilize at room temperature. The mixed solution is prepared by adding the alcohol having 1 to 4 carbon atoms and water to the silicon alkoxide, and preferably stirring the mixture at a temperature of 10° C. to 30° C. for 30 minutes or more.

[0037] A catalyst is added to and mixed with the mixed solution prepared above. In a case where the silica sol gel liquid is regarded as 100% by mass, it is preferable that the silica sol gel liquid contains, as a proportion, 2% by mass to 50% by mass of the silicon alkoxide, 20% by mass to 98% by mass of the alcohol having 1 to 4 carbon atoms, 0.01% by mass to 5% by mass of the catalyst, and 0.01% by mass to 5% by mass of the additive. Examples of the catalyst include organic acids, inorganic acids, and organic compounds. Examples of the additive include formamide described above, and acetylacetone. In this case, a liquid temperature is preferably maintained at a temperature of 10° C. to 30° C., and the mixture is stirred for preferably 1 hour to 24 hours. The silica sol gel liquid is thus prepared.

[0038] The above-described catalyst is used to promote hydrolysis reaction. Examples of the organic acid include formic acid and oxalic acid, and examples of the inorganic acid include hydrochloric acid, nitric acid, and phosphoric acid. The catalyst is not limited to those described above. The reason why a proportion of the above-described catalyst is limited to the above-described range is that, in a case of being below the lower limit value, the film is not formed due to poor reactivity and insufficient polymerization, and even in a case of being above the upper limit value, there is no effect on the reactivity, but the residual acid tends to cause corrosion or the like on the substrate on which the film is formed.

[0039] The amount SiO.sub.2 (hereinafter, referred to as an equivalent SiO.sub.2 concentration) in the silica sol gel liquid, which corresponds to SiO.sub.2 generated from the silica sol gel liquid, is preferably 1% by mass to 40% by mass, and more preferably 5% by mass to 20% by mass. In a case where the equivalent SiO.sub.2 concentration is below the lower limit value, the polymerization is insufficient, bonding property between the Y.sub.2O.sub.3 particles, which will be described later, is poor, and the Y.sub.2O.sub.3 particles tend to fall off from the SiO.sub.2 film. In addition, deterioration of the adhesion of the film and generation of cracks are likely to occur. Furthermore, in a case of being above the upper limit value, the viscosity of the silica sol gel liquid increases, and coating properties of the silica sol gel liquid tend to deteriorate.

[0040] [Sol Gel Liquid for Forming Plasma-Resistant Coating Film]

[0041] The sol gel liquid for forming a plasma-resistant coating film according to the present embodiment is prepared by mixing the Y.sub.2O.sub.3 particles with the silica sol gel liquid using a stirrer such as a magnetic stirrer. The mixing is preferably carried out so that the above-described Y.sub.2O.sub.3 particles have a concentration proportion of 0.1 g/mL to 2.5 g/mL in the above-described sol gel liquid for forming a plasma-resistant coating film. In a case where the concentration of the Y.sub.2O.sub.3 particles is less than 0.1 g/mL, it is difficult to increase a film density of the plasma-resistant coating film to 90% or more, and in a case of being more than 2.5 g/mL, the sol gel liquid for forming a plasma-resistant coating film does not become liquid, and coating on the surface of the substrate tends to be poor. The mixing proportion thereof is more preferably 1.5 g/mL to 2 g/mL.

[0042] In the sol gel liquid for forming a plasma-resistant coating film according to the present embodiment, since the crystalline Y.sub.2O.sub.3 particles having a predetermined average particle diameter is uniformly dispersed at a predetermined concentration, in a case of being applied onto the surface of the substrate, dried, and further subjected to a heat treatment as will be described later, the crystalline Y.sub.2O.sub.3 particles are contained in the SiO.sub.2 film on the substrate, and the crystalline Y.sub.2O.sub.3 particles are bonded to each other and arranged to form a dense and high-density crystalline Y.sub.2O.sub.3 film.

[0043] In the sol gel liquid for forming a plasma-resistant coating film according to the present embodiment, in addition to the Y.sub.2O.sub.3 particles, YF.sub.3 particles may be contained at a concentration proportion of 0.1 g/mL to 1.0 g/mL. In a case of containing the YF.sub.3 particles, a film having higher plasma resistance is obtained.

[0044] [Method for Forming Plasma-Resistant Coating Film on Surface of Substrate]

[0045] As shown in FIGS. 1 and 2, in a case where the sol gel liquid 17 for forming a plasma-resistant coating film is applied onto the substrate 10, dried at a temperature of 70° C. to 100° C. under an air atmosphere, and subjected to a heat treatment at 250° C. to 400° C., preferably 250° C. to 350° C., the silica sol gel component contained in the sol gel liquid 17 for forming a plasma-resistant coating film becomes a SiO.sub.2 film (silica sol gel) 16a, and dispersed crystalline Y.sub.2O.sub.3 particles 11a and 11b are bonded to each other by the SiO.sub.2 film and arranged on the substrate 10. As a result, a plasma-resistant coating film 20 according to the present embodiment is formed on the surface of the substrate 10. That is, a substrate 30 with a plasma-resistant coating film, including the substrate 10 and the plasma-resistant coating film 20 formed on the surface of the substrate 10, is obtained.

[0046] In a case where the temperature of the heat treatment is lower than 250° C., adhesion of the formed film to the surface of the substrate is deteriorated. In a case of being higher than 400° C., a substrate which does not have high heat resistance, such as aluminum, is thermally deformed, and it is not possible to form a uniform plasma-resistant coating film. In order to obtain a desired film thickness, the procedure from the application onto the substrate to the heat treatment may be repeated one or more times.

[0047] Various materials can be adopted as the substrate depending on the application. In particular, examples of a preferred material of the substrate include aluminum, alumina, silicon, silicon oxide, and quartz, which are usually used as a plasma treatment apparatus part. In addition, examples of the method of coating the sol gel liquid for forming a plasma-resistant coating film include spin coating, screen-printing, bar coating, die coating, doctor blade, brush coating, dipping, and spraying.

[0048] As shown in FIG. 1, in the plasma-resistant coating film 20 formed on the surface of the substrate 10, a plurality of crystalline Y.sub.2O.sub.3 particles 11a and 11b having an average particle diameter of 0.5 μm to 5.0 μm are dispersed in the SiO.sub.2 film. In a case where the crystalline Y.sub.2O.sub.3 particles are composed of small-diameter first particles 11a and large-diameter second particles 11b, the small-diameter first particles 11a are placed in voids between the large-diameter second particles 11b, and the Y.sub.2O.sub.3 particles are densely dispersed in the SiO.sub.2 film. The SiO.sub.2 film is formed on the surface of the substrate 10 with high adhesion. The film thickness of the plasma-resistant coating film according to the present embodiment is preferably 10 μm to 300 μm, and more preferably 150 μm to 250 μm. In a case where the film thickness is less than 10 μm, the service life of the plasma-resistant coating film tends to be short. In a case where the film thickness is more than 300 μm, the cracks are likely to occur in the film.

[0049] In addition, in the present embodiment, the plasma-resistant coating film may include pores having a diameter of 5 μm or less, but does not include pores (voids) having a diameter of more than 5 μm. This is because, in a case where a large pore of more than 5 μm exists, a problem arises in that etching is accelerated due to non-uniform voltage application in the vicinity of the pore.

[0050] Furthermore, the plasma-resistant coating film according to the present embodiment may include the YF.sub.3 particles in addition to the Y.sub.2O.sub.3 particles. In a case of containing the YF.sub.3 particles, a film having higher plasma resistance is obtained.

[0051] In the plasma-resistant coating film according to the present embodiment, a film density of the plasma-resistant coating film is 90% or more, preferably 95% or more, the film density being obtained by performing image analysis of a cross section of the film with an electron scanning microscope (manufactured by Hitachi, Ltd., model name: NB5000) and by using the following expression (1). However, in the expression (1), S.sub.1 is an area of the film in a portion of 10 μm×30 μm, analyzed by the image analysis, and S.sub.2 is an area of a pore portion in the film of the portion.

Film density (%)=[(S.sub.1−S.sub.2)/S.sub.1]×100  (1)

[0052] In addition, the plasma-resistant coating film according to the present embodiment a peeling rate of the film from the substrate measured by performing a cross-cut test is 5% or less, preferably 10% or less. Specifically, in the cross-cut test of the film, the plasma-resistant coating film (film thickness: 20 μm) formed on a substrate of a mirror surface-processed silicon substrate is cross-cut in 1 mm width in a grid pattern, an adhesive tape (manufactured by NICHIBAN Co., Ltd., product name “Cellotape (registered trademark)”) is applied to the cross-cut film in the grid pattern, and a Cellotape (registered trademark) peeling test (hereinafter, simply referred to as a peeling test) is conducted in accordance with a grid pattern tape method of JIS K5600-5-6 (cross-cut method). 100 cross-cut squares are expressed as the denominator, the number of squares remaining on the substrate after the peeling test is expressed as the numerator, and a proportion of completely peeled squares to the 100 squares is the peeling rate (%). That is, the peeling rate is expressed as (number of peeling parts/number of cut parts)×100. Here, the number of peeling parts corresponds to the number of squares in which the film is completely peeled off from the substrate by performing the cross-cut test.

EXAMPLES

[0053] Next, Examples of the present invention will be described in detail together with Comparative Examples.

Example 1

[0054] First Y.sub.2O.sub.3 particles and second Y.sub.2O.sub.3 particles were mixed with each other such that a mass ratio (second particles/first particles) of the second particles to the first particles was 2. On the other hand, hydrochloric acid and acetylacetone were added to a mixed solution of tetraethoxysilane (TEOS) and 1-butanol, and mixed at room temperature of 25° C. for 3 hours to obtain a silica sol gel liquid. The equivalent SiO.sub.2 concentration (amount SiO.sub.2) in the silica sol gel liquid excluding the solvent was 10% by mass. A mixed solution of the silica sol gel liquid, the first Y.sub.2O.sub.3 particles, and the second Y.sub.2O.sub.3 particles was mixed such that the concentration of Y.sub.2O.sub.3 particles was 2 g/mL to prepare a sol gel liquid for forming a plasma-resistant coating film. The sol gel liquid was applied onto a silicon substrate by spin coating, dried at 75° C., and subjected to a heat treatment at 300° C. under an air atmosphere to form a plasma-resistant coating film containing the Y.sub.2O.sub.3 particles in the SiO.sub.2 film.

[0055] Table 1 below shows preparation conditions and heat treatment temperatures during film formation for each sol gel liquid for forming a plasma-resistant coating film of Example 1, and Examples 2 to 8 and Comparative Examples 2 and 3 described later.

[0056] The average particle diameter of the Y.sub.2O.sub.3 particles in the sol gel liquid forming a plasma-resistant coating film was measured by a laser diffraction and scattering method using MT3000 manufactured by Microtrac Retsch GmbH. The average particle diameter was D50: median diameter.

TABLE-US-00001 TABLE 1 Sol gel liquid for forming plasma-resistant coating film Crystalline Y.sub.2O.sub.3 particles Film Average Average Ratio of second Silica sol Average formation particle particle particles to gel liquid particles condition diameter diameter first particles Equivalent SiO.sub.2 Concentration diameter Heat of first of second (mass ratio) concentration of Y.sub.2O.sub.3 of Y.sub.2O.sub.3 treatment particles particles (second particles/ (amount SiO.sub.2) particles particle temperature (μm) (μm) first particles) (% by mass) (g/mL) (μm) (° C.) Example 1 1 3 3 10 2 1.23 300 Example 2 1 3 3 10 2 1.18 400 Example 3 1 3 1 10 2 1.10 300 Example 4 1 3 3 10 1.5 1.22 250 Example 5 — 3 — 10 2 3.05 300 Example 6 1 — — 10 2 1.01 300 Example 7   0.5 5 3 10 2 0.51 300 Example 8 — 5 — 10 2 5.00 300 Comparative — — — — — — — Example 1 Comparative 5 10  1 10 2 6.10 300 Example 2 Comparative 1 3 3 10 2 1.22 200 Example 3

Examples 2 to 4

[0057] In Examples 2 to 4, the same first Y.sub.2O.sub.3 particles and second Y.sub.2O.sub.3 particles as in Example 1 were used, and the mass ratio (second particles/first particles) of the second particles to the first particles was varied or the same as in Example 1, as shown in Table 1. In addition, the equivalent SiO.sub.2 concentration in the silica sol gel liquid excluding the solvent and the concentration of the Y.sub.2O.sub.3 particles in the sol gel liquid for forming a plasma-resistant coating film was varied or the same as in Example 1, as shown in Table 1. A plasma-resistant coating film was formed on the silicon substrate in the same manner as in Example 1, except that the heat treatment temperature of the obtained sol gel liquid for forming a plasma-resistant coating film was varied or the same as in Example 1.

Examples 5, 6, and 8

[0058] In Example 5, only a dispersion liquid of second Y.sub.2O.sub.3 particles, in which Y.sub.2O.sub.3 particles (second particles) having an average particle diameter of 3 μm were dispersed, was used. In Example 6, only a dispersion liquid of first Y.sub.2O.sub.3 particles, in which Y.sub.2O.sub.3 particles (first particles) having an average particle diameter of 1 μm were dispersed, was used. In Example 8, only a dispersion liquid of second Y.sub.2O.sub.3 particles, in which Y.sub.2O.sub.3 particles (second particles) having an average particle diameter of 5 μm were dispersed, was used. In Examples 5, 6, and 8, except for the above, the silica sol gel liquid shown in Table 1 was used to adjust the concentration of the Y.sub.2O.sub.3 particles. A plasma-resistant coating film was formed on the silicon substrate in the same manner as in Example 1 in a state that the heat treatment temperature of the obtained sol gel liquid for forming a plasma-resistant coating film was the same as in Example 1.

Example 7

[0059] In Example 7, as shown in Table 1, Y.sub.2O.sub.3 particles (first particles) having an average particle diameter of 0.5 μm and Y.sub.2O.sub.3 particles (second particles) having an average particle diameter of 5 μm were mixed such that the mass ratio of the second particles to the first particles was 3, and a silica sol gel liquid having an equivalent SiO.sub.2 concentration excluding the solvent, as shown in Table 1, was further mixed to prepare a sol gel liquid for forming a plasma-resistant coating film having a concentration of the Y.sub.2O.sub.3 particles as shown in Table 1. Thereafter, a plasma-resistant coating film was obtained as shown in Table 1.

Comparative Example 1

[0060] In Comparative Example 1, a plasma-resistant coating film was formed by the thermal spraying method disclosed in Patent Document 1.

Comparative Example 2

[0061] In Comparative Example 2, as shown in Table 1, Y.sub.2O.sub.3 particles (first particles) having an average particle diameter of 5 μm and Y.sub.2O.sub.3 particles (second particles) having an average particle diameter of 10 μm were mixed such that the mass ratio of the second particles to the first particles was 1, and a silica sol gel liquid having an equivalent SiO.sub.2 concentration excluding the solvent, as shown in Table 1, was further mixed to prepare a sol gel liquid for forming a plasma-resistant coating film having a concentration of the Y.sub.2O.sub.3 particles as shown in Table 1.

Comparative Example 3

[0062] In Comparative Example 3, the same sol gel liquid for forming a plasma-resistant coating film as in Example 1 was prepared, but the heat treatment temperature was changed to 200° C. A plasma-resistant coating film was obtained in the same manner as in Example 1 except for the above.

[0063] <Comparative Test and Evaluation>

[0064] With regard to the 11 kinds of plasma-resistant coating films obtained in Examples 1 to 8 and Comparative Examples 1 to 3, (a) a film density, (b) a peeling rate from the substrate, (c) an atomic concentration ratio (Y/Si) of yttrium (Y) to silicon (Si) on the surface of the coating film, (d) a film thickness, (e) a half width of a main peak for a Y.sub.2O.sub.3 crystal in X-ray diffraction of the film, appearing in a range of 2θ=29 degrees to 29.5 degrees, (f) the presence or absence of pores having a diameter of more than 5 μm in the film, and (g) the average particle diameter of the Y.sub.2O.sub.3 particles in the film were measured.

[0065] The (a) film density and the (b) peeling rate from the substrate were measured by the methods described above. The (c) atomic concentration ratio was measured with energy dispersive X-ray spectroscopy (EDS, manufactured by Bruker, model name: QUANTAX). The (d) film thickness was measured by SEM cross section method. In addition, the (e) half width was measured with an X-ray diffraction (XRD) device (manufactured by Rigaku Corporation, model name: RINT Ultima III).

[0066] In addition, for the (f) presence or absence of pores, a cross section of the film was imaged at 10 random locations with an electron scanning microscope (manufactured by Hitachi, Ltd., model name: NB5000) at a magnification of 1000 times, and in a case where there was no pore larger than 5 μm in terms of diameter corresponding to the area circle (diameter of the circle having the same area), it was evaluated as “absence”, and in a case where there was at least one pore larger than 5 μm, it was evaluated as “presence”. Furthermore, the (g) average particle diameter of the Y.sub.2O.sub.3 particles was measured with electron beam backscatter diffraction (EBSD, manufactured by TSL Solutions Co., Ltd., Hikari). As for the measurement conditions, the average particle diameter was calculated by image analysis of the particle diameter of the film area portion of 10 μm×30 μm with a visual field image magnified by 10000 times. An area circle equivalent diameter was used for the average particle diameter. These results are shown in Table 2 below.

TABLE-US-00002 TABLE 2 Evaluation of plasma-resistant coating film Average Presence particle (Y/Si) or absence diameter Film Peeling (atomic Film Half of pores of Y.sub.2O.sub.3 density rate concentration thickness width larger than particles (%) (%) ratio) (μm) (degree) 5 μm (μm) Example 1 98.7 0 6 80 0.19 Absence 1.25 Example 2 99 0 5 80 0.19 Absence 1.20 Example 3 99 1 5 80 0.20 Absence 1.10 Example 4 96 4 6 80 0.18 Absence 1.20 Example 5 94 0 6 80 0.19 Absence 3.10 Example 6 94 2 4.5 80 0.17 Absence 1.00 Example 7 96 3 7 60 0.19 Absence 0.50 Example 8 90 5 4 60 0.19 Absence 5.00 Comparative 96 1 0 200 0.20 Presence — Example 1 Comparative 60 1 10 150 0.18 Absence 6.00 Example 2 Comparative 96 35 6 100 0.19 Absence 1.20 Example 3

[0067] As is clear from Table 2, since the plasma-resistant coating film of Comparative Example 1 was formed by the thermal spraying method, the film density was as high as 96%, but there were pores larger than 5 μm and the result was “presence”. Therefore, it was expected that the film would be easily etched when irradiated with plasma in a plasma treatment apparatus, and that the plasma resistance would not be high.

[0068] Since the plasma-resistant coating film of Comparative Example 2 contained the Y.sub.2O.sub.3 particles (second particles) having an average particle diameter of 10 μm in addition to the Y.sub.2O.sub.3 particles (first particles) having an average particle diameter of 5 μm, the film density was as low as 60%. In addition, the average particle diameter of the Y.sub.2O.sub.3 particles in the film was 6.00 μm, and cracks were observed in the film.

[0069] In the plasma-resistant coating film of Comparative Example 3, since the heat treatment temperature was as low as 200° C., the film density was as high as 96%, but the peeling rate of the film was as high as 35% and the adhesion of the film to the substrate was poor.

[0070] On the other hand, since the plasma-resistant coating films of Examples 1 to 8 contained a plurality of crystalline Y.sub.2O.sub.3 particles having an average particle diameter of 0.5 μm to 5.0 μm in the SiO.sub.2 film, the scope of the invention of the first aspect, that the film density was 90% or more, the size of pores in the film was 5 μm or less in diameter, and the peeling rate of the film from the substrate was 5% or less, was satisfied.

[0071] In particular, in Examples 1, 4, and 7 in which the crystalline Y.sub.2O.sub.3 particles were composed of the first particles having an average particle diameter of 0.5 μm to 1 μm and the second particles having an average particle diameter of 3 μm to 5 μm, the film density was as high as 96% or more, and high adhesion was exhibited.

INDUSTRIAL APPLICABILITY

[0072] The plasma-resistant coating film according to the present invention is used as a protective film for a plasma treatment apparatus part that is irradiated with plasma in a plasma treatment apparatus.

REFERENCE SIGNS LIST

[0073] 10: Substrate [0074] 11a: Y.sub.2O.sub.3 particles (small-diameter first particles) [0075] 11b: Y.sub.2O.sub.3 particles (large-diameter second particles) [0076] 16a: Silica sol gel [0077] 20: Plasma-resistant coating film [0078] 30: Substrate with a plasma-resistant coating film