DESCRIPTION Y ₂ O ₃ film and process for producing the same

Technical field

The present invention relates to a member having excellent resistance to plasma corrosion and a process for producing the member. The present invention includes an Y2O3 film which is formed on a substrate using an Y ₂ Q3 nanoparticle slurry as a raw material in order to enhance resistance to plasma corrosion, a member and a process for forming the film.

The plasma corrosion-resistant member of the invention is applicable to a plasma etching chamber of a semiconductor manufacturing apparatus or a plasma treatment apparatus for a liquid crystal device or the like.

Background art

Examples of substrates generally used for members of a plasma etching apparatus that is an apparatus for manufacturing semiconductors and liquid crystal devices include a metal material, such as Al or Al alloy, an

anodized film of Al formed on a surface of the metal material, and a film of a sintered product, such as Al ₂ O ₃ or Si ₃ N4. It is known that these materials suffer chemical damages when they are brought into contact with highly corrosive halogen ions or suffer corrosion damages due to fine parties, such as SiO ₂ or Si ₃ N ₄ , and due to ions excited by plasma.

In order to enhance plasma corrosion resistance of the substrates, techniques for forming films of oxides, carbides and nitrides of Y, Sc, La, Ce, Yb, Eu, Dy and the like are known. As the methods for forming Y ₂ O ₃ films, there are known, for example, a PVD method, a CVD method (patent document 1), a thermal spraying method (patent document 2) and a sol-gel method (patent document 3) . Of the above methods, the PVD method and the CVD method have a low film-forming rate and are poor in productivity. Further, the CVD method is limited in applications, that is, this method cannot be used when the decomposition temperature of the CVD material is higher than the heat-resistant temperature of the substrate, and in case of, for example, aluminum used for an etching chamber, the upper limit of the heat-resistant temperature is in the range of 300 ⁰ C to 400 ⁰ C, so that application of the CVD method to aluminum is difficult.

In case of the thermal spraying method and the sol- gel method, there are many defects in the resulting films, and in order to completely coat a substrate with Y ₂ O3, a large film thickness of about 300 nm is necessary. Unless such a large film thickness of about 300 nm is given, a continuous defect reaching the substrate takes place, and sufficient plasma corrosion resistance cannot be obtained. In addition to this problem, the conventional sol-gel method has a problem of chamber interior contamination derived from a silicic acid salt because a silicic acid salt is added as a binder in order to prevent scattering of Y2O3 fine particles in the plasma treatment or improve bonding between the resulting film and the substrate. Patent document 1: Japanese Patent Laid-Open Publication No. 4083/1998

Patent document 2: Japanese Patent No. 3510993 Patent document 3: Japanese Patent Laid-Open Publication No. 335589/2003

Disclosure of the invention

It is an object of the present invention to provide a member coated with a dense Y ₂ O ₃ film which can be formed

under the low-temperature conditions and exhibits sufficient plasma corrosion resistance even in a film thickness of 200 nm to 50 μm.

The present inventors have earnestly studied in view of the prior art as mentioned above, and as a result, they have made the present invention of the following constitution.

(1) A process for producing an Y ₂ O3 film, comprising drying an Y ₂ O3 slurry having a volume-average particle, diameter, in a dispersed state, of 10 nm to 300 nm and heat-treating the dried product.

(2) The process for producing an Y ₂ O3 film as stated in (1), comprising applying an Y ₂ O3 slurry having a volume-average particle diameter, in a dispersed state, of 10 nm to 300 nm, drying the slurry and heat-treating the dried product.

(3) The process for producing an Y2O3 film as stated in (1) or (2) , wherein a polyhydric alcohol derivative is used as a dispersion medium of the Y ₂ O3 slurry. (4) The process for producing an Y ₂ O3 film as stated in any one of (1) to (3), wherein the Y ₂ O ₃ slurry contains β-diketone as a dispersant.

(5) The process for producing an Y2O3 film as stated in any one of (1) to (4), wherein the Y ₂ O3 slurry contains a β-diketone metal complex as a binder.

(6) The process for producing an Y2O3 film as stated in any one of (1) to (5), wherein the Y ₂ O3 slurry is a mixed slurry of two or more kinds of slurries having dispersed particle diameters of different volume-average particle diameters .

(7) The process for producing an Y2O3 film as stated in any one of (1) to (6), wherein the Y ₂ O3 slurry is a dispersion of Y ₂ O ₃ particles in a dispersion medium, said Y ₂ O ₃ particles being prepared by vapor phase oxidation of a β-diketone metal complex.

(8) The process for producing an Y2O3 film as stated in any one of (1) to (7) , wherein an Y ₂ O ₃ slurry having a volume-average particle diameter, in a dispersed state, of 10 nm to 300 nm and having an Y ₂ O3 concentration of 0.1% by mass to 40% by mass is applied onto a substrate once or plural times so that the film thickness based on one film-forming operation should become 10 nm to 5 μm, and heat treatment after film formation is carried out at a heat treatment temperature of 100 ⁰ C to 300 ⁰ C for a heat treatment time of 10 minutes to 5 hours.

(9) An Y ₂ O3 film comprising an aggregate of Y2O3 particles having a volume-average particle diameter of 10 nm to 300 nm.

(10) The Y ₂ O ₃ film as stated in (9), which is a film for an etching chamber member.

(11) An Y ₂ O ₃ film produced by the process of any one of (1) to (8) .

(12) A member coated with the film of any one of (9) to (11) . (13) An etching chamber member coated with the film of any one of (9) to (11) .

(14) An etching chamber having the etching chamber member of (13) .

According to the present invention, a dense and strong film of Y ₂ O ₃ can be readily formed on a surface of a plasma treatment container or a surface of a member in the plasma treatment container at a low temperature without selecting a material of a substrate, as described above. Further, the film is excellent in that a metal that becomes a contamination source when it is used for a semiconductor manufacturing apparatus is not contained. Moreover, the member provided with the film by the invention is markedly superior to thermal spraying films in the plasma erosion resistance in an atmosphere

containing a halogen compound, in spite of a small film thickness. Therefore, the cost for film formation can be greatly decreased, and besides, it becomes possible to efficiently manufacture high-quality products because contamination of the chamber interior with particles is low even if plasma treatment is continued over a long period of time.

In the present invention, a dispersant and a binder may be added to the Y2O ₃ slurry. In this case, by selecting a dispersant and a binder each of which does not contain a metal that becomes a contamination source when the slurry is used for a semiconductor manufacturing apparatus, a film causing no contamination of the chamber interior can be formed. Moreover, the film formed by the invention is excellent in various properties generally required for films, such as film hardness, bonding to a substrate and heat cycle resistance.

Brief description of Drawings

Fig. 1 is a schematic view of an apparatus for preparing Y2O3 nanoparticles .

Fig. 2 is a schematic view of spray equipment for applying an Y ₂ O ₃ slurry.

Fig. 3 is an electron microscope photograph of an Y ₂ O3 film (glass substrate) of Example 3.

Best mode for carrying out the invention

The Y ₂ O ₃ film and the process for producing the film according to the invention are described in detail hereinafter. Y ₂ O ₃ film The Y ₂ O ₃ film of the invention comprises an aggregate of Y ₂ O ₃ particles having a volume-average particle diameter of 10 nm to 300 nm. The term "aggregate" referred to herein means a state where the Y ₂ O ₃ nanoparticles physically adhere to one another very firmly by van der Waals force or the like or they are chemically bonded (sintered) to one another. This film is extremely dense and has no continuous defect reaching a substrate, so that the film exhibits sufficient plasma corrosion resistance even in a film thickness of 200 nm

to 50 μiα. In this film, a dispersant, a binder and the like may be contained, when needed.

It can be confirmed that the film comprises an aggregate of Y ₂ O ₃ nanoparticles having a volume-average particle diameter of 10 nm to 300 nm, by measuring

diameters of the particles (not less than 100 particles) from a photograph taken by an electron microscope, determining a particle size distribution and calculating a volume-average particle diameter. Also in case of a distribution having two peaks, the same calculation as above is carried out. Y ₂ O ₃ slurry

The Y ₂ O ₃ film of the invention is formed by the use of an Y ₂ O ₃ slurry having a particle diameter, in a dispersed state, of 10 nm to 300 nm (volume-average particle diameter) . The particle diameter in a dispersed state means a volume average value measured when the particles are in a state of a slurry in which they are dispersed (or in a state of a slurry diluted with a dispersion medium) , and it can be measured by a laser Doppler method.

The particle diameter of the Y ₂ O ₃ particles in a dispersed state in a slurry is more preferably 10 nm to 200 nm, most preferably 10 nm to 100 nm. Such Y ₂ O ₃ particles having a particle diameter of nano order are referred to as "Y ₂ O ₃ nanoparticles" . If the particle diameter in a dispersed state exceeds 300 nm, aggregation of particles becomes insufficient in the heat treatment at a low temperature, so that the temperature for the

heat treatment needs to be raised, and as a result, it becomes difficult to use a substrate having a low heat- resistant temperature (e.g., aluminum plate) . If the heat treatment temperature is lowered, aggregation of Y ₂ O ₃ nanoparticles does not proceed. As a result, a film defect becomes large, and in order to satisfy desired plasma corrosion resistance, a film of larger thickness is necessary.

If the particle diameter in a dispersed state is , made smaller than needed, great energy is consumed for the dispersing operation itself.

For producing the Y ₂ O ₃ nanoparticles, a vapor phase process (Japanese Patent Laid-Open Publication No. . 168641/2004), a co-precipitation process (Japanese Patent Laid-Open Publication No. 127773/1996) or the like can be appropriately selected. For dispersing the nanoparticles in a dispersion medium, an ultrasonic method, a ball mill method, a bead mill method or the like can be appropriately selected. In the bead mill method, zirconia or the like is employable as a material of the bead, and beads having diameters of 5 μm to 1 mm are employable .

Dispersion medium of Y ₂ O ₃ slurry

The dispersion medium of the Y2O3 slurry is desirably a polyhydric alcohol derivative. The Y2O3 nanoparticles exhibit extremely strong mutual interactions and have properties such that they are liable to be aggregated, but by the use of the above dispersion medium, it becomes possible to disperse the Y ₂ O ₃ nanoparticles with almost no aggregation. The dispersing quality of the dispersion medium greatly varies depending upon the type of the dispersion medium, and from the viewpoints of dipole moment, viscosity and the like, a polyhydric alcohol derivative is preferable.

The polyhydric alchol derivative is preferably a monoether, diether, monoeser or diester of a polyhydric alcohol. Examples of the polyhydric alcohol derivatives include derivatives of dihydric alcohols, such as 1- methoxy-2-propanol, l-ethoxy-2-propanol, l-butoxy-2- propanol, diethylene glycol ethylmethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether, ethylene glycol diacetate, ethylene glycol diethyl ether, ethylene glycol dibutyl ether,

ethylene glycol dimethyl ether, ethylene glycol monoacetate, ethylene glycol monoisopropyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, ethylene glycol monohexyl ether, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate and ethylene glycol monomethoxyrαethyl ether; and derivatives of trihydric or higher polyhydric alcohols, such as glycerol monoacetate, glycerol diacetate, glycerol triacetate, glycerol dialkyl ether (e.g., 1, 2-dimethylglycerol, 1,3- dimethylglycerol, 1, 3-diethylglycerol) . Of these, 1- methoxy-2-propanol is particularly preferable. Dispersant of slurry The Y ₂ O3 slurry may contain a dispersant. In the present invention, β-diketone, which does not contain an alkali metal or the like that is avoided in the use for a semiconductor manufacturing apparatus, proved to be particularly useful as a dispersant. As β-diketone, 2, 2, 6, 6-tetramethylheptane-3, 5-dione (DPM-H), 2, 6-dimethyl-3,5-heptanedione (DMHD-H), 2,4- pentanedione (acac-H) or the like is employable. In

addition to β-diketone, also employable are β-ketoesters, such as methyl-3-oxopentanoate, ethyl-3-oxopentanoate,

rαethyl-4-methyl-3-oxopentanoate, ethyl-4-methyl-3- oxopentanoate, methyl~4, 4-dimethyl-3-oxopentanoate and ethyl-4 , 4-dimethyl-3-oxopentanoate .

By the use of such a dispersant, decrease of an ultimate particle diameter of dispersed particles, shortening of dispersing time and prevention of re- aggregation after dispersing become possible. Further, because the β-diketone is volatile, it is vaporized in the heat treatment after coating operation and does not remain in the resulting film. The β-diketone is added in an amount of 1 part by mass to 10 parts by mass, preferably 5 parts by mass to 10 parts by mass, based on 100 parts by mass of Y2O3.

In combination with the β-diketone, a nonionic surfactant can be added as a dispersant. Examples of the nonionic surfactants include those of ether type, such as polyoxyethylene alkyl. ether, polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene, polyoxypropylene block copolymer and polyoxyethylene polyoxypropylene alkyl ether; those of ester ether type, such as polyoxyethylene glycerol fatty acid ester, polyoxyethylene castor oil, polyoxyethylene hardened castor oil and polyoxyethylene sorbitol fatty acid ester. The nonionic surfactant is added in an

amount of 1 part by mass to 10 parts by mass, preferably 5 parts by mass to 10 parts by mass, based on 100 parts by mass of Y2O3.

If the amount of the dispersant is too large, the dispersant remains as impurities in the film, and the impurities derived from the dispersant are scattered in the plasma treatment, or pinholes formed by scatting of the dispersant sometimes cause corrosion of a member, so that such an amount is undesirable. If the amount of the dispersant is too small, sufficient dispersion effect is not obtained. Binder

In the Y2O ₃ slurry, a β-diketone metal complex, which does not contain an alkali metal or the like that is avoided in the use for a semiconductor manufacturing apparatus, may be contained as a binder.

By the use of such a binder, lowering of a temperature in the heat treatment of the Y2O3 particles, increase of cohesive force of the nanoparticles in the film and increase of bonding between the film and a member become possible.

As the metal for constituting the complex, yttrium is preferable.

As the β-diketone metal complex, an yttrium complex of 2,2, 6, 6-tetramethylheptane~3, 5-dione (DPM-H), 2,6- dimethyl-3, 5-heptanedione (DMHD-H), 2, 4-pentanedione (acac-H) or the like is employable, and specifically, Y (DPM) 3, Y (DMHD) 3, Y(acac)3 or the like is employable. In addition to the metal complex of the β-diketone compound, also employable are metal complexes of β- ketoesters, such as metal complexes of methyl-3- oxopentanoate, ethyl-3-oxopentanoate, methyl-4-methyl-3- oxopentanoate, ethyl-4-methyl-3-oxopentanoate, methyl- 4, 4-dimethyl-3-oxopentanoate and ethyl-4, 4-dimethyl-3- oxopentanoate .

The β-diketone metal complex is added in an amount of 1 part by mass to 10 parts by mass, preferably 5 parts by mass to 10 parts by mass, based on 100 parts by mass of Y ₂ O ₃ . If the amount of the binder is too large, the binder remains as impurities in the film, and the impurities derived from the binder are scattered in the plasma treatment, or pinholes formed by scatting of the binder sometimes cause corrosion of a member. If the amount of the binder is too small, sufficient dispersion effect is not obtained. Y ₂ O ₃ nanoparticles

For producing Y2O3 nanoparticles to be dispersed in the slurry of the invention, vapor phase oxidation of a

β-diketone metal complex is employable. One example of this process is a process comprising mixing vapor containing a gaseous β-diketone metal complex obtained by vaporizing a solution of a β-diketone metal complex with an oxygen-containing gas or oxygen, quantitatively feeding the mixture to a heating device such as a tubular electric furnace and allowing the β-diketone metal complex to undergo thermal decomposition/oxidation reaction to obtain metal oxide fine particles. Other processes publicly known, such as co-precipitation, are also employable.

The Y ₂ O ₃ nanoparticles obtained by the vapor phase oxidation of a β-diketone metal complex usually contain several % of a carbon residue as impurities. If the amount of the carbon residue is large, the carbon residue remains as impurities in the film, and the carbon is scattered in the plasma treatment, or pinholes formed by scattering of the carbon cause corrosion, so that such an amount is undesirable. In order to avoid such a phenomenon, it is preferable to carry out calcining treatment at 100 ⁰ C to 1000 ⁰ C for 1 to 12 hours in an

atmosphere of air to decrease the amount of the carbon residue after the treatment to less than 0.5% by mass.

The Y ₂ O ₃ nanoparticles synthesized by the above process are present in the form of aggregates, and in order to obtain a stable slurry, it is necessary to pulverize and finely disperse the aggregates by a proper method and to stably maintain the dispersed state. As methods to finely disperse the aggregates, various methods, such as a bead mill method, a jet mill method and a ball mill method, are known. For dispersing the nanoparticles, a bead mill method is preferable. As the size of the bead used is reduced, further increase of a dispersing rate and further decrease of an ultimate, particle diameter can be made, so that it is preferable to use beads having a diameter of 5 μm to 200 μm, particularly 10 μm to 100 μm. From the viewpoint of minimization of contamination of the slurry by impurities, the material of the beads is preferably zirconium oxide having excellent abrasion resistance. For preparing the Y ₂ O ₃ slurry using a bead mill, the Y ₂ O ₃ nanoparticles, the organic dispersion medium, the dispersant, the binder and the beads are filled in a container, and they are stirred. The filling proportion of the beads to the container is in the range of

preferably 85% to 95%, and the Y2O ₃ nanoparticles are used in amounts of 1% by mass to 50% by mass based on the total 100% by mass of the Y2O3 nanoparticles, the organic dispersion medium, the dispersant and the binder. Although the stirring time is properly determined according to the desired ultimate particle diameter of dispersed particles, it is in the range of usually about 10 minutes to 12 hours. The dispersed particle diameter of the Y ₂ O ₃ nanoparticles in the resulting slurry is in the range of preferably 10 nm to 200 nm, more preferably 10 nm to 100 nm.

Prior to preparation of the slurry using a bead mill, appropriate dispersing of the particles by ultrasonic irradiation, a rotational and revolutional mixer or the like may be carried out as a pretreatment . Particle size distribution of Y2O3 slurry

The Y ₂ O ₃ slurry is desirably a mixed slurry of two or more kinds of slurries having dispersed particle diameters of different volume-average particle diameters. When slurries having different dispersed particle diameters are mixed, small particles enter gaps among large particles, whereby further densification of the film becomes possible. For example, a combination of a distribution peak diameter of 200 nm to 300 nm and a

distribution peak diameter of 10 nm and 100 run, or a combination of a distribution peak diameter of 300 nm to 200 nm and a distribution peak diameter of 10 nm and 50 nm is applicable. With regard to a difference in the dispersed particle diameter, a difference between the distribution peak diameters is desirably in the range of 50 to 200 nm. Formation of Y ₂ O ₃ film

In the present invention, after the Y ₂ O3 slurry was applied onto a substrate and dried, heat treatment is carried out to obtain an Y2O3 film. By optimizing slurry concentration, coating weight based on one coating operation, heat treatment conditions, etc., a dense and strong Y ₂ O ₃ film free from cracks and pinholes can be formed.

Substrate

Preferred examples of the substrates to be coated with the Y ₂ O ₃ film include aluminum and aluminum alloy which are used for semiconductor manufacturing apparatuses or the like, various iron and steel materials including stainless steel, tungsten, tungsten alloy, titanium, titanium alloy, molybdenum, molybdenum alloy, oxide type ceramics such as glass, carbon, and non-oxide type ceramics. Prior to the film formation, these

substrates may have been subjected to blasting if necessary, or may have been provided with a film composed of a metal material having high resistance to halogen gas corrosion. Application of Y2O3 slurry

In the application of the slurry to the substrate, the slurry has an Y ₂ O ₃ concentration of 0.1% by mass to 40% by mass, more preferably 0.5% by mass to 10% by mass. If the concentration of the slurry is too high, the film sometimes suffers cracks. If the concentration is too low, productivity is lowered.

Application of the slurry to the substrate and drying of the slurry are repeated to form a film of a desired thickness. The film thickness based on one film- forming operation is in the range of usually 10 ruα to 5 μm, more preferably 100 nm to 3 μm. If the film thickness based on one film-forming operation is too large, the film sometimes suffers cracks. If the film thickness based on one film-forming operation is too small, productivity is lowered. The film thickness based on one film-forming operation can be controlled by slurry concentration, slurry viscosity, coating weight, etc.

The final thickness of the Y ₂ O ₃ film is in the range

of 0.05 μm to 500 μra, preferably 0.5 μm to 50 μm.

Although conventional Y ₂ O ₃ films need to have a thickness

of not less than 300 μm, the film of the invention exhibits sufficient plasma resistance even in a thickness

of not more than 50 μm. A method of applying the slurry can be appropriately selected from conventional methods, such as air spraying, dip coating and spin coating, according to the size, shape, etc. of the substrate to be coated. Heat treatment of Y2O3 The heat treatment temperature after application of the slurry is in the range of preferably 100 to 300°C, more preferably 200 to 300 ⁰ C. Even if the heat treatment temperature is higher than 300 ⁰ C, aggregation of nanoparticles proceeds and no problem takes place particularly, but it is difficult to apply such a high temperature to a member of low heat resistance such as aluminum. If the heat treatment temperature is too low, aggregation does not proceed and many defects are produced in the film, sometimes resulting in troubles such as lowering of film strength and remaining of a dispersant and a binder as impurities in the film. The heat treatment time is in the range of preferably 10 minutes to 5 hours, more preferably 30 minutes to 1 hour. The result of heat treatment of long time and the result

of heat treatment of short time are the same as the result of heat treatment of high temperature and the result of heat treatment of low temperature, respectively.

For the heat treatment, a rectangular or cylindrical electric calcining furnace, a microwave calcining furnace or the like is employable. However, the heat treatment effect is obtained also by irradiation with plasma. Depending upon cleanness required for the film, application of the slurry and heat treatment may be carried out in the clean environment such as a clean room or a clean booth. Examples of formation of Y2O3 film

Formation of an Y ₂ O ₃ film by air spraying is carried out in the following manner. The Y2O3 slurry is diluted to 0.1% by mass to 40% by mass with an organic dispersion medium (preferably the same dispersion medium in the Y ₂ O ₃ slurry) . The diluted .slurry is sprayed onto a member using air spray equipment and then dried for 1 minute to 1 hour to volatilize the organic dispersion medium. Then, heat treatment is carried out at 100 ⁰ C to 300 ⁰ C for 10 minutes to 5 hours in an atmosphere of air to promote aggregation of the Y ₂ O ₃ nanoparticles and to bring about decomposition/oxidation reaction of the binder, whereby a

dense and strong Y ₂ O ₃ film is formed on a surface of the member .

Although the film thickness based on one film- forming operation is properly determined according to the dilution concentration of the slurry and the quantity of the slurry sprayed, it is preferable to carry out the operation so that the film thickness should become 10 nm to 5 μm, preferably 100 nm to 3 μm, after drying. If the film thickness based on one film-forming operation is, too large, the film suffers cracks, and if the film thickness based on one film-forming operation is too small, productivity is lowered, so that such a thickness is undesirable. The heat treatment temperature after application of the slurry is in the range of preferably 200 ⁰ C to 300 ⁰ C. If the heat treatment temperature is high, aggregation of nanoparticles proceeds but it is difficult to apply a high temperature to a member of low heat resistance such as aluminum. If the heat treatment temperature is too low, aggregation does not proceed and many defects are produced in the film, resulting in troubles such as lowering of film strength and remaining of a dispersant and a binder as impurities in the film, so that such a temperature is undesirable.

Similarly to the above, formation of an Y2O3 film by dip coating is carried out in the following manner. The Y ₂ O ₃ slurry is diluted to 0.1% by mass to 40% by mass with an organic dispersion medium (preferably the same dispersion medium in the Y ₂ O3 slurry) . The diluted slurry is applied to a member using dip coating equipment and then dried for 1 minute to 1 hour to volatilize the organic dispersion medium. Then, heat treatment is carried out at 100 ⁰ C to 300 ⁰ C for 10 minutes to 5 hours in an atmosphere of air to promote aggregation of the Y2O ₃ nanoparticles and to bring about decomposition/oxidation reaction of the binder, whereby a dense and strong Y ₂ O ₃ film is formed on a surface of the member. Although the film thickness based on one film-forming operation is properly determined according to the dilution concentration of the slurry and the pull-up rate of the member, it is preferable to carry out the operation so that the film thickness should become 10 nm to 5 μm, preferably 100 nm to 3 μm, after drying. If the film thickness based on one film-forming operation is too large, the film sometimes suffers cracks, and if the film thickness based on one film-forming operation is too small, productivity is sometimes lowered. The heat treatment temperature after application of the slurry is

in the range of preferably 200 ⁰ C to 300 ⁰ C. If the heat treatment temperature is high, aggregation of nanoparticles proceeds but it is difficult to apply a high temperature to a member of low heat resistance such as aluminum. If the heat treatment temperature is too low, aggregation does not proceed and many defects are produced in the film, sometimes resulting in troubles such as lowering of film strength and remaining of a dispersant and a binder as impurities in the film. Similarly to the above, formation of an Y ₂ O ₃ film by spin coating is carried out in the following manner. The Y ₂ O ₃ slurry is diluted to 0.1% by mass to 40% by mass with an organic dispersion medium (preferably the same dispersion medium in the Y2O3 slurry) . The diluted slurry is applied to a member using spin coating equipment and then dried for 1 minute to 1 hour to volatilize the organic dispersion medium. Then, heat treatment is carried out at 100 ⁰ C to 300 ⁰ C for 10 minutes to 5 hours in an atmosphere of air to promote aggregation of the Y ₂ O ₃ nanoparticles and to bring about decomposition/oxidation reaction of the binder, whereby a dense and strong Y ₂ O ₃ film is formed on a surface of the member. Although the film thickness based on one film-forming operation is properly determined according to the dilution

concentration of the slurry, the quantity of the slurry dropped, and the number of revolutions and the revolution time of the member, it is preferable to carry out the operation so that the film thickness should become 10 nm to 5 μm, preferably 100 nm to 3 μm, after drying. If the film thickness based on one film-forming operation is too large, the film sometimes suffers cracks, and if the film thickness based on one film-forming operation is too small, productivity is sometimes lowered. The final thickness of the Y ₂ O3 film is in the range of 0.05 μm to 500 μm, preferably 0.5 μm to 50 μm. Member

The member of the invention is obtained by forming the above-described Y2O3 film on a surface of a substrate. Although the thickness of the Y2O3 film formed is not specifically restricted, it is in the range of preferably

0.05 μm to 500 μm.

Examples of the substrates include those previously described. The member of the invention is particularly preferably an etching chamber member. Since the member of the invention has high resistance to plasma corrosion, the member is preferably used for, for example, a plasma etching chamber and a plasma treatment apparatus for a liquid crystal device or the like.

Examples

The present invention is further described with reference to the following examples, but it should be construed that the invention is in no way limited to those examples.

Preparation Example 1 Using an apparatus having a constitution shown in Fig. 1, Y ₂ O ₃ nanoparticles were prepared. First, to a vaporizer (6) heated to 200 ⁰ C, a mixed solution of 300 g of yttrium tridipivaloylmethane and 700 g of methanol was fed at a flow rate of 4 ml/min, and the solution was vaporized. To a preheater (5) , air was fed as an oxidizing substance (1) at a flow rate of 40 1/min, and the air was heated to 200 °C. Then, the gaseous yttrium tridipivaloylmethane and methanol, and the air were fed to a coaxial nozzle at an entrance of a tubular electric furnace (7) . The combustion temperature in the tubular electric furnace was set at 950 ⁰ C, and the yttrium tridipivaloylmethane and methanol were oxidized to form Y ₂ O ₃ . A yield of the Y ₂ O ₃ nanoparticles collected by a collector (8) was not less than 95%.

The Y ₂ O ₃ nanoparticles contained several % of a carbon residue as impurities . To remove the carbon residue, calcining treatment was carried out at 500 ⁰ C for 8 hours in an atmosphere of air. As a result of thermogravitometry using a thermobalance device

(manufactured by Seiko Instruments Inc., TG/DTA6200) , the amount of the carbon residue was less than 0.5% by mass. As a result of observation under a field emission type scanning electron microscope (manufactured by Hitachi, Ltd., S-900) , the primary particle diameter of the Y ₂ O ₃ particles was about 20 nm.

Preparation Example 2

To 400 ml of an yttrium nitrate solution (1 mol/1) heated to 8O ⁰ C, 1.65 liters of an ammonium oxalate solution (0.4 mol/1) were dropwise added over a period of 1 hour with stirring.. After the dropwise addition was completed, stirring was carried out at 80 ⁰ C for 1 hour. After the stirring was completed, the mixture was cooled to room temperature, and the resulting precipitate was filtered. The precipitate was further subjected to filtration washing with 2 liters of water. The precipitate was vacuum dried at 80 ⁰ C to obtain yttrium oxalate. The dried precipitate was placed in a porcelain

crucible and calcined at 700 ⁰ C for 3 hours in an atmosphere of air to obtain Y ₂ O ₃ . A yield of the resulting Y2O ₃ nanoparticles was not less than 99%. As a result of observation under an electron microscope, the primary particle diameter of the Y2O3 particles was about 20 nm.

Example 1

15 g of the Y ₂ O ₃ nanoparticles obtained in Preparation Example 1 and 352 g of l-methoxy-2-propanol were mixed. To the mixture, 1.5 g of acetylacetone as a dispersant 1, 1.5 g of a water-slightly soluble triol- based dispersant (available from Asahi Denka Co., Ltd., ADEKA CARPOLE GL-100) as a dispersant 2 and 5 g of yttrium triacetylacetone as a binder were added, and the resulting mixture was subjected to ultrasonic treatment for 1 hour to obtain a homogeneous slurry. The slurry was treated by a bead mill (manufactured by Kotobuki Engineering & Manufacturing Co., Ltd., UAM-015) containing 400 g of zirconium oxide beads having a diameter of 50 μm for 6 hours to obtain an Y ₂ O ₃ slurry of 4% by mass. As a result of measurement of a dispersed particle size distribution of the slurry by a particle size distribution meter (manufactured by Nikkiso Co.,

Ltd., Nanotrac UPA-EX150) , the volume-average particle diameter was 18 nm, and the maximum particle diameter was 102 nm.

Example 2

An Y ₂ O ₃ slurry of 4% by mass was obtained in the same manner as in Example 1, except that 15 g of the Y ₂ O ₃ nanoparticles obtained in Preparation Example 2 were used. As a result of measurement of a dispersed particle size distribution of the slurry by a particle size distribution meter, the volume-average particle diameter was 20 nm, and the maximum particle diameter was 102 nm, said results being equivalent to those of the slurry obtained in Example 1.

Comparative Example 1

15 g of the Y2O3 nanoparticles obtained in Preparation Example 1 and 360 g of methanol were mixed, and the resulting mixture was subjected to ultrasonic treatment for 1 hour to obtain a homogeneous slurry. The slurry was treated by a bead mill in the same manner as in Example 1. As a result of measurement of a dispersed particle size distribution of the slurry by a particle size distribution meter, the volume-average particle

diameter was 890 nm, and the maximum particle diameter was 3270 nm.

The results are set forth in Table 1.

Table 1

Dmin=the minimum particle diameter, Dav=volume-average particle diameter, Dmax=the maximum particle diameter

Example 3

The Y2O3 slurries obtained in Examples 1 and 2 were each diluted with l-methoxy-2-propanol so that the Y ₂ O ₃ concentration should become 1% by mass. The diluted slurry was sprayed onto an aluminum specimen as a substrate (size: 50 mm (width) x 50 mm (length) x 5 mm (thickness) ) by means of such air spray equipment as shown in Fig. 2 and dried for 5 minutes in an atmosphere of air to volatilize l-methoxy-2-propanol. The specimen' was heat-treated at 300 ⁰ C for 1 hour in an atmosphere of air to form an Y ₂ O ₃ film on the specimen surface. The

film thickness based on one film-forming operation was made 200 nm, and this operation was repeated 5 times to

produce a film having a thickness of 1 μrα. Further, the film thickness based on one film-forming operation was made 1 μm, and this operation was repeated 10 times to produce a film having a thickness of 10 μm. Furthermore, the film thickness based on film-forming operation was made 2 μm, and this operation was repeated 25 times to produce a film having a thickness of 50 μm. Also on a glass specimen, production of a film having a thickness of 1 μm was carried out. The film thickness was measured by the aforesaid field emission type scanning electron microscope. An electron microscope photograph of the film having a thickness of 1 μm produced on the glass substrate using the slurry of Example 1 is shown in Fig. 3. The film proved to be a dense film because it was formed from nanoparticles .

Comparative Example 2

Y ₂ Oa film having a thickness of 1 μm are formed on an aluminum specimen and a glass specimen, respectively, in the same manner as Example 3 except that the Y ₂ O ₃ slurry obtained in Example 1 was diluted with methanol so that the Y ₂ O ₃ concentration should become 1% by mass.

Example 4

The Y ₂ O ₃ slurry obtained in Example 1 was diluted with l-methoxy-2-propanol so that the Y2O3 concentration should become 1% by mass. The diluted slurry was applied onto an aluminum specimen (size: 50 mm (width) x 50 mm (length) x 5 mm (thickness) ) by the use of dip coating equipment (pull-up rate: 3 cm/min) and dried for 5 minutes in an atmosphere of air to volatilize 1-methoxy- 2-propanol . The specimen was heat-treated at 300 ⁰ C for 1 hour in an atmosphere of air to form an Y2O3 film on the specimen surface. This operation was repeated to obtain a film having a thickness of 1 μm, a film having a thickness of 10 μm and a film having a thickness of 50 μm.

Example 5

The Y ₂ O3 slurry obtained in Example 1 was diluted with l-methoxy-2-propanol so that the Y2O3 concentration should become 1% by mass. The diluted slurry was applied onto an aluminum specimen (size: 50 mm (width) x 50 mm (length) x 5 mm (thickness) ) by the use of spin coating equipment (number of revolutions: 30 rpm, 30 seconds) and dried for 5 minutes in an atmosphere of air to volatilize l-methoxy-2-propanol. The specimen was heat-treated at

300 ⁰ C for 1 hour in an atmosphere of air to form an Y ₂ O ₃ film on the specimen surface. This operation was

repeated to obtain a film having a thickness of 1 μm, a film having a thickness of 10 μm and a film having a thickness of 50 μm.

Comparative Examples 3 and 4

On a surface of an aluminum specimen (size: 50 mm (width) x 50 mm (length) x 5 mm (thickness) ) as a substrate, an Y ₂ O ₃ thermal spraying film was formed by means of atmospheric plasma thermal spraying. The plasma thermal spraying is a method wherein an Y ₂ O ₃ powder as a plasma thermal spraying material is heated by a plasma jet to give molten droplets and the molten droplets are sprayed onto a substrate at a high speed. In these examples, a thermal spraying film having a film thickness

of 100 μm and a thermal spraying film having a film thickness of 300 μm were produced under the conditions of a supply current of 850 A, a plasma feed gas flow rate of 85 1/min, an Y ₂ O ₃ powder feed rate of 5 g/min and a spray distance of 100 mm.

Test

The specimens prepared in Examples 3 to 5 and Comparative Examples 2 to 5 were subjected to bond strength measurement and thermal shock test (test wherein operations of heating a specimen for 20 minutes in an electric furnace kept at 500 ⁰ C and quenching it outside the furnace were taken as one cycle and this cycle is repeated ten times) .

Further, the aluminum specimens were each subjected to plasma etching treatment under the following conditions, then the number of particles adhering to a surface of a silicon wafer of 8-inch diameter having been allowed to stand still in a chamber was measured, and a period of time taken until the number of particles exceeded a control limit of a general chamber interior, i.e., 30, was measured. The surface inspection equipment used was equipment to . count the number of particles utilizing scattering of a laser beam, and the number of particles having a particle diameter of not less than 0.2 μm was measured.

(1) Gas flow rate: NF ₃ /Ar/O ₂ = 100/200/80 (flow rate, cm ³ per minute)

(2) Pressure: 3.5 (Pa)

(3) High-frequency power: 800 (W)

The results are set forth in Table 2

Table 2

The bond strength is measured in accordance with JIS-H8666 (ceramic thermal spraying film test method) .

With regard to the films obtained by air spraying in Example 3, it was confirmed that irrespective of type of specimen and film thickness, the bond strength was markedly higher than that of Comparative Examples 2 to 4, similarly to the Y ₂ O ₃ slurries obtained in Examples 1 and 2. Further, it was also confirmed that irrespective of

film thickness, the time taken until the number of particles exceeded 30 was sufficiently longer than that of the thermal spraying films of comparative Examples 3 and 4, and in spite that the film thickness was small, the plasma erosion resistance in an atmosphere containing a halogen compound was markedly higher than that of the thermal spraying films.

With regard to also the films obtained by dip coating in Example 4 and the films obtained by spin coating in Example 5, it was confirmed that irrespective of film thickness, the bond strength was markedly higher than that of the thermal spraying films of Comparative Examples 3 and 4, the time taken until the number of particles exceeded 30 was sufficiently longer than that of the thermal spraying films, and in spite that the film thickness was small, the plasma erosion resistance in an atmosphere containing a halogen compound was markedly higher than that of the thermal spraying films, similarly to the films obtained by air spraying. In the examples and the comparative examples, there was no film suffering peeling in the thermal shock test.