JP5212607B2 - Method for forming rare earth oxide film - Google Patents

Description

  The present invention relates to a method for forming a rare earth (Group 3A) oxide film.

  Rare earth oxides are used as corrosion-resistant coatings on the walls of processing chambers that come into contact with plasma, such as plasma etching apparatuses, due to their good plasma resistance. For this plasma-resistant coating, a plasma spraying method is mainly employed because of ease of formation and cost (Japanese Patent Laid-Open No. 2001-164354: Patent Document 1). However, the coating surface formed by plasma spraying has large irregularities due to adhesion of unmelted particles or fine particles evaporated or precipitated in high-temperature plasma, or cracks caused by melting, collision, or rapid cooling. Is liable to be detached and causes contamination to the semiconductor wafer. On the other hand, dense smooth films such as PVD methods such as sputtering and CVD have been studied, but they are high cost methods such as vacuum processes and cannot be applied to members having complicated shapes. A sol-gel coating method has been proposed as a method for solving this problem, and it is said that a dense smooth film can be obtained by a relatively simple process (Japanese Patent Laid-Open No. 2007-27329: Patent Document 2).

  In addition, rare earth oxides are difficult to adsorb mercury vapor, and a rare earth oxide film is formed on the inner surface of the glass bulb to prevent luminance deterioration caused by the glass bulb of a fluorescent lamp adsorbing mercury vapor inside. To be done.

  In this formation method, a sol-gel method in which a sol of rare earth oxide or its precursor fine particles is applied, dried, and fired, and a solution of a rare earth compound that becomes a rare earth oxide by thermal decomposition is applied, dried, and thermally decomposed. There is a way to do it.

  However, such sol-gel method and solution coating method have a common problem in that a solvent is used. In other words, the sol-gel method has a problem that shrinkage occurs due to evaporation of the solvent when the sol is dried, and cracks are likely to occur. In addition, since the precursor sol is produced by hydrolysis of an alkoxide or the like, a large amount of an organic solvent is often used, and there are also problems in cost and environment. In addition, the solution coating method has the same problems, and the solute is likely to be partially crystallized and unevenly distributed when the solvent is evaporated, making it difficult to obtain a dense and smooth film. Furthermore, if it is intended to obtain a certain film thickness by these methods, it is necessary to coat a film of 0.1 μm or less several tens to several hundreds of times, which is expensive.

JP 2001-164354 A JP 2007-27329 A

  This invention is made | formed in view of the said situation, and it aims at providing the formation method of the rare earth oxide film from which the precise | minute and smooth rare earth oxide film can be obtained simply.

  As a result of intensive studies in order to achieve the above object, the present inventor has used a rare earth organic complex having a non-decomposable melting point without using a solvent, and formed a film with the melt in a heated and melted state. It has been found that a dense and smooth rare earth oxide film can be formed by forming and thermally decomposing it in an oxidizing atmosphere, and has reached the present invention.

Accordingly, the present invention provides the following method for forming a rare earth oxide film.
[1] Non-decomposable melting point, 8-quinolinol, dipivaloylmethane, 2,4-pentanedione, benzoylacetone, β-diketones, aromatic carboxylic acid, 1,10-phenanthroline, 2,2 ′ -An organic complex of a rare earth element having a ligand selected from bipyridine and triphenylphosphine oxide is heated and melted below the decomposition temperature of the organic complex, a film is formed by the melt, and this is heated to oxidatively decompose A method for forming a rare earth oxide film.
(2) from the heat-melted to the film forming method for forming a rare earth oxide coating according to the content of water vapor and carrying out in an atmosphere of less than 1% by volume in the atmosphere [1].
[3] from heat melting to film forming method for forming a rare earth oxide coating according to the content of oxygen is equal to or performed under an atmosphere of less than 1 volume% in an atmosphere (1) or (2) .

  According to the present invention, a dense and smooth rare earth oxide film can be easily obtained by an organic complex melt film formation method, and its utility value is extremely high in industry.

Hereinafter, the present invention will be described in detail. The method for forming a rare earth oxide film of the present invention is characterized in that a melt of a rare earth organic complex having a non-decomposable melting point is formed and oxidatively decomposed.
First, the rare earth elements referred to in the present invention are Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
For applications that transmit light, such as when a rare earth element oxide is used as a protective film on the inner surface of a glass bulb of a fluorescent lamp, it is better that the oxide itself is colorless and transparent, especially Sc, Y, La, Gd, Yb. , Lu is preferred.

  The rare earth element organic complex that is a precursor of the rare earth oxide film preferably has a non-decomposable melting point, and the ligand includes 8-quinolinol, dipivaloylmethane, 2,4-pentanedione, benzoyl. It can be selected from acetone, other β-diketones, aromatic carboxylic acids, 1,10-phenanthroline, 2,2′-bipyridine, triphenylphosphine oxide, and the like.

As the composition of the complex, for example,
Tris (8-quinolinolato) _{(8-quinolinol) RE = [RE (C 9} H 6 NO) 3 (C 9 H 7 NO)],
Tris (benzoylacetonato) RE = [RE (C ₁₀ H ₉ O ₂ ) ₃ ],
Tris (2,4-pentanedionato) RE = [RE (C ₅ H ₇ O ₂ ) ₃ ]
(RE is a rare earth element)
Etc. These melting points are usually in the range of 100 to 140 ° C, and the decomposition temperature is usually in the range of 140 to 180 ° C.

These organic complexes are heated and melted below the decomposition temperature of the organic complex to form a film on the substrate. As the melting temperature, the metal complex is melted at a melting point or higher and lower than a decomposition temperature depending on the type of the complex. Various methods such as doctor blade, spin coating, roll coating, brush coating, and dip coating can be selected as a method for forming a film of the molten rare earth element organic complex, but are not limited thereto. Moreover, when apply | coating to a glass tube inner wall etc., melt suction application | coating is possible.
The film thickness is preferably 1 to 500 μm, more preferably 5 to 100 μm.

  In these film forming methods, it is preferable to control the substrate, the coating equipment, and the atmosphere all at a constant temperature in the non-decomposition melting temperature range of the organic complex. If the substrate, equipment, or atmosphere is lower than the melting temperature, the film may partially solidify or the melt viscosity may change and a uniform film may not be formed. On the other hand, when the temperature is higher than the decomposition start temperature of the organic complex, the film may be partially decomposed and solidified, or the melt viscosity may change and a uniform film may not be formed.

  The atmosphere at the time of film formation by the melt is preferably an inert gas atmosphere such as nitrogen or argon which does not substantially contain oxygen or water vapor. This is because the presence of oxygen and water vapor narrows the temperature range obtained by melting the organic complex without decomposing, making it difficult to control the temperature. Here, “substantially free” means that the content of oxygen or water vapor is 1% by volume or less, particularly 0.1% by volume or less in the atmosphere.

  The organic complex film obtained as described above is baked in an oxidizing atmosphere (air, oxygen-containing gas) and converted into an oxide film. The temperature is changed to 400 to 1,500 ° C, preferably 400 to 1,000 ° C. If the firing temperature is too low, the film may not be completely converted to an oxide, and if it is too high, a crack may occur in the film. The firing time is preferably 1 to 100 hours, and more preferably 5 to 25 hours. Moreover, although the thickness of an oxide film is suitably selected, it is preferable that it is 0.1-100 micrometers, especially 1-50 micrometers.

  Examples of the substrate on which the film is formed include carbon, metal (Al, SUS), ceramic (alumina, zirconia, silicon nitride, boron nitride), quartz, and the like.

  The coating film of the present invention can be used as a protective film for a processing chamber wall member and a fluorescent lamp glass bulb inner wall that are in contact with plasma of a plasma etching apparatus.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Example 1]
A stainless steel plate of 100 mm × 100 mm × 2 mmt was heated to 130 ° C. in a closed container purged with nitrogen containing less than 0.1% by volume of oxygen and water vapor, and tris (benzoylacetonato) yttrium salt (melting point 114 ° C., decomposition point) (140 ° C.) 0.1 g was dropped on the surface, and after confirming that the whole was melted, a film was formed with a doctor blade having a gap of 5 μm that had been heated to 130 ° C. in advance. This was baked at 550 ° C. for 8 hours in the atmosphere to obtain a yttrium oxide coating on the surface. When the surface and cross section were observed with an electron microscope, a film having a thickness of about 1 μm was formed, but it was a dense smooth film free from cracks and foreign matter.

[Example 2]
A quartz glass plate of 100 mm × 100 mm × 2 mmt was heated to 150 ° C. in the sealed container described in Example 1, and 0 of tris (2,4-pentanedione) erbium salt (melting point 140 ° C., decomposition point 165 ° C.) was obtained. .1 g was dropped on the surface, and after confirming that the whole was melted, a film was formed with a doctor blade having a gap of 5 μm that had been heated to 150 ° C. in advance. This was baked at 550 ° C. for 8 hours in the atmosphere to obtain a coating of erbium oxide on the surface. When the surface and cross section were observed with an electron microscope, a film having a thickness of about 1 μm was formed, but it was a dense smooth film free from cracks and foreign matter.

[Comparative Example 1]
A 5% by mass ethanol solution of yttrium isopropoxide was applied to a 100 mm × 100 mm × 2 mmt aluminum plate by a dip coating method, gelled, and dried. This operation was repeated 20 times and then fired at 500 ° C. in the atmosphere. When the surface was observed with an electron microscope, a dense film having a thickness of about 1 μm was formed, but cracks having a width of 1 to several tens of μm were observed in various places.

[Comparative Example 2]
A 5% by mass ethanol solution of tris (2,4-pentanedione) erbium salt was applied to a 100 mm × 100 mm × 2 mmt quartz glass plate by a dip coating method, dried, and fired at 550 ° C. in the atmosphere. After repeating this operation 10 times, when the surface was observed with an electron microscope, it was confirmed that erbium oxide particles having an irregular shape of about 5 μm were unevenly distributed on the quartz glass surface. It is considered that crystals of the organic complex were precipitated, and these were transformed into oxides by thermal decomposition while losing their shape.

Claims (3)

It has a non-decomposing melting point, 8-quinolinol, dipivaloylmethane, 2,4-pentanedione, benzoylacetone, β-diketones, aromatic carboxylic acid, 1,10-phenanthroline, 2,2′-bipyridine, And an organic complex of a rare earth element having a ligand selected from triphenylphosphine oxide is heated and melted below the decomposition temperature of the organic complex, a film is formed by the melt, and this is heated to oxidatively decompose. A method for forming a rare earth oxide film. From heat melting to film forming method for forming a rare earth oxide film according to claim 1 in which the content of water vapor and carrying out at 1% by volume under the following ambient atmosphere. From heat melting to film forming method for forming a rare earth oxide film according to claim 1 or 2 content and performing in an atmosphere of less than 1 volume% in an atmosphere of oxygen.