JPH0829932B2 - Method for improving film quality of silica-based coating - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the quality of a silica-based film, and more particularly to a method for improving the density and etching resistance of a silica-based film formed on a substrate surface. .

(Prior Art) Silica-based coatings have been widely used in various applications in recent years. For example, surface stabilizing films or interlayer insulating films of semiconductor devices; insulating films or alignment control films of liquid crystal display devices; ceramics, plastics or metals. It is used as a surface protection film against.

The properties required for silica coatings used in such applications are that they are uniform without defects such as pinholes and cracks, have excellent mechanical strength, and have excellent chemical resistance and moisture resistance. Is.

Among these properties, mechanical strength, chemical resistance, and moisture resistance are known to be greatly influenced by the denseness of the silica-based coating itself, and this denseness generally increases the refractive index of the coating and It can be evaluated by the reduction of the film reduction rate by the etching treatment. Conventionally, there has been proposed a method of applying a heat treatment after depositing a silica-based coating in order to improve the density of the silica-based coating (Japanese Patent Publication No. 52-37353). This heat treatment is usually performed in an atmosphere of oxygen, nitrogen or air.

Further, a method has also been proposed in which the silica-based coating is irradiated with ultraviolet rays in the atmosphere to increase the denseness of the silica-based coating. This method has the effect of improving the denseness as compared with the method of only heat treatment.

(Problems to be Solved by the Invention) According to the above-mentioned conventional method, densification of the silica-based coating can be achieved to some extent, but pinholes and cracks are still liable to occur, and the film characteristics are inferior. Properties required for the silica-based coating to be used cannot be satisfied.

Further, in the case of the method of irradiating with ultraviolet rays, since it is processed in the atmosphere, it is not possible to sufficiently remove the hydroxyl groups from the silica-based coating and it is not possible to completely mineralize it. Therefore, pinholes and cracks may occur, which is not a complete method for treating a silica-based coating used for electronic parts.

(Means for Solving Problems) As a result of intensive studies to solve the above problems, the present invention has found that it is effective to irradiate a silica-based coating film with ultraviolet rays under reduced pressure. The findings have led to the present invention.

That is, the present invention is characterized in that the silica coating is irradiated with ultraviolet rays under reduced pressure.

(Example) Hereinafter, the present invention will be described in detail.

As the silica-based coating used in the method of the present invention, in addition to a method using a coating liquid for forming a silica-based coating containing an organic solvent solution of a silicon compound as a main component (coating method), a CVD method,
It can be formed by a sputtering method, a vapor phase growth method, or the like, but the coating method is particularly advantageous because it has higher production efficiency than other methods.

The silica-based coating film forming coating solution used in the coating solution contains an organic solvent solution of a silicon compound as a main component, and a halogenated silane or an alkoxysilane is useful as the silicon compound. Halogenated silane is
General formula R _n SiX _4-n (wherein X is a halogen atom, R is an alkyl group, an aryl group, a glycidoxyalkyl group or a vinyl group, and n is 0 or an integer of 1 to 3) A compound represented by, for example, silicon tetrachloride, silicon tetrabromide, tetrachlorosilane, dibromodichlorosilane, vinyltrichlorosilane, methyltrichlorosilane, ethyltrichlorosilane, phenyltrichlorosilane, dimethyldichlorosilane, diphenyldichlorosilane, diethyl. Examples thereof include dichlorosilane and β-glycidoxyethyltrichlorosilane.

The alkoxysilane has the general formula (RO) _n SiX _4-n or (RO) _n SiR ′ _4-n (wherein X is a halogen atom, R and R ′ are each independently an alkyl group, an aryl group, Glycidoxyalkyl group,
An acryloxyalkyl group, a methacryloxyalkyl group or a vinyl group, and n is 0 or an integer of 1 to 4), for example, monomethoxytrichlorosilane, dimethoxydichlorosilane, trimethoxymonochlorosilane, Monoethoxytrichlorosilane,
Diethoxydichlorosilane, triethoxymonochlorosilane, monoallyloxytrichlorosilane, diaryloxydichlorosilane, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, monomethyltrimethoxysilane, monoethyltrimethoxysilane, monomethyl Triethoxysilane, monoethyltriethoxysilane, monoethyltributoxysilane, monophenyltrimethoxysilane, monophenyltriethoxysilane, dimethyldimethoxysilane, diethyldiethoxysilane, diphenyldimethoxysilane,
Diphenyldiethoxysilane, diethyldibutoxysilane, vinylmethyldimethoxysilane, vinylethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyl Triethoxysilane, β-methacryloxyethyltrimethoxysilane, β-methacryloxyethyltriethoxysilane, β-glycidoxyethyltrimethoxysilane, β-glycidoxyethyltriethoxysilane, γ-glycidoxypropyltrimethoxy Silane, γ
-Glycidoxypropyltriethoxysilane and the like can be mentioned.

The above-mentioned halogenated silanes and alkoxysilanes can be used alone or in combination of two or more.

These silicon compounds are dissolved in an organic solvent and prepared as a coating liquid, but as the organic solvent used,
Alcohols, esters, ketones and aromatic hydrocarbons are preferable, and examples of alcohols include methanol, ethanol, propanol, butanol, cyclohexanol, benzyl alcohol, dimethylolbenzene, furfuryl alcohol and tetrahydrofurfuryl. Examples thereof include alcohol, diacetone alcohol, ethylene glycol monoalkyl ether, diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, and propylene glycol monoalkyl ether. Examples of the esters include acetic acid alkyl ester and diethylene glycol monoalkyl ether. Acetate, triethylene glycol monoalkyl ether acetate, propylene glycol monoalkyl ether Ether acetate, ethyl acetoacetate, alkyl lactate, alkyl benzoate, benzyl acetate, and glycerin diacetate. Examples of ketones include acetone, methyl ethyl ketone, cyclohexanone, acetylacetone, isophorone, diethyl ketone,
Methyl isobutyl ketone, methyl n-butyl ketone, acetonyl acetone, etc. can be mentioned, and examples of the aromatic hydrocarbons include benzene, toluene, xylene, ethylbenzene, diethylbenzene, cumene, tetralin and the like. These may be used alone or in combination of two or more.

The solution obtained by dissolving the above-mentioned silicon compound in an organic solvent and concentrating it can be used as a coating liquid for forming a silica-based film, but usually, an organic solvent containing a hydrolyzate of the above-mentioned silicon compound. A solution obtained by preparing a solution and concentrating it is preferably used as a coating liquid for forming a silica-based film.

As a method for preparing an organic solvent solution containing a hydrolyzate, for example, a method of adding water and an organic acid or an inorganic acid to an organic solvent solution of a silicon compound, or a reaction product of a halogenated silane and a carboxylic acid is reacted with an alcohol. And a method of adding an inorganic acid to a mixture of an alkoxysilane, an organic carboxylic acid and an alcohol (Japanese Patent Publication No. 56-34234), and the like. A hydrolyzate of a silicon compound, which is easily produced, is dissolved in the above-mentioned organic solvent to a concentration of usually 1 to 50% by weight, preferably 2 to 20% by weight, and this solution is then heated to a temperature of less than 200 ° C (pressure reduction if necessary). By performing _a dehydration condensation reaction in (below) and adjusting the viscosity to about 2 × 10 ^{−3 to} 0.2 Pa _{· s} , a practically suitable coating liquid for forming a silica-based coating film can be obtained.

In addition, the coating solution for forming a silica-based film, if necessary, as a vitreous forming agent, Li, B, Na, K, Fe, Ni, Cr, Mg,
Al, P, Ca, Ti, Zr, Mo, In, Sn, Sb, Ba, Ta, W, Mn, Pb, Pt, Au, Ce and other metal halides, hydroxides, oxides, inorganic acid salts , Organic acid salts, alkoxy compounds, chelate compounds and organometallic compounds can be added. The addition amount of these is 1 to 50% by weight in terms of metal, based on the silicon compound.
Is preferred.

These silica-based coating film forming liquids are applied to substrates such as glass, ceramics, metals, and silicon wafers by a conventional method such as a spinner method, a dipping method, a spray method, and a printing method to a predetermined film thickness, and 200 ° C. A silica-based coating is formed on the substrate by drying at the temperature below.

In the method of the present invention, the above silica-based coating is irradiated with ultraviolet rays under reduced pressure, and an example of an apparatus used for carrying out the method will be described with reference to the drawings.

A chamber 3 made of aluminum, synthetic quartz, or the like is provided on the opening 2 formed in the table 1, and an ultraviolet ray generation lamp 4 is arranged in the chamber 3.
An illuminance monitor 5 and a gas introduction pipe 6 are attached to the.

Here, examples of the ultraviolet ray generating lamp 4 include a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, and a xenon lamp.
Irradiance at a wavelength of 7 nm is 10 mW / cm ² or more and 1
A device that outputs a wavelength of 85 nm is preferable.

Further, an exhaust passage 7 communicating with the outside is formed in the table 1, and a stage 8 which moves up and down from the bottom faces the opening 2, and a substrate W on which a silica coating 10 is formed is mounted on the stage 8. A heating member 9 such as a hot plate whose temperature can be controlled is embedded inside.

When the method of the present invention is shown by the apparatus shown in the drawings, after the substrate W on which the silica-based coating is formed is placed on the stage 8, the stage 8 is raised to seal the opening 2 and the inside of the chamber 3 is exhausted. The pressure is reduced by a vacuum pressure reducing device (not shown) provided at the end of the passage 7. Then, after adjusting to a predetermined vacuum degree, the ultraviolet lamp 4 is applied to the silica coating 10.
To irradiate ultraviolet rays. In this case, the pressure in the chamber 3 is usually 4000Pa or less, and especially 1500Pa.
The following are practically preferable. When the pressure is higher than this, the effect of the present invention cannot be sufficiently achieved, which is not preferable. Further, in the method of the present invention, it is preferable to irradiate with ultraviolet rays while heating the substrate W by the heating member 9 embedded in the stage 8. The heating temperature is equal to or lower than the heat treatment temperature applied after the treatment of the method of the present invention. Temperature is good, specifically
It is less than 400 ° C, preferably 100 to 300 ° C.

By performing the above treatment, it is possible to reduce the OH groups in the film, which adversely affects the film properties of the silica-based film, so that the denseness of the entire film is improved, and there are no pinholes or cracks in the silica-based film. A coating can be obtained. Further, the effect can be further improved by performing heat treatment in an inert gas such as nitrogen after the above treatment. For such post-treatment, by using the apparatus shown in the drawing, an inert gas such as nitrogen gas is introduced into the chamber 3 through the gas introduction port 6 and the heating member 9 is used to irradiate ultraviolet rays. Although it is preferable that the treatment can be performed after the treatment, the post-treatment may be performed by another heat treatment apparatus. The ultraviolet lamp may be provided inside or outside the chamber.

Next, examples and comparative examples will be described with specific numerical values to further clarify the effect of the method of the present invention.

Example 1 OCD Type-6 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), which is a coating liquid for forming a silica-based coating film containing a hydrolyzate of alkoxysilane, was applied onto a 4-inch silicon wafer by a spinner method at 3000 rpm for 20 seconds, After drying at 140 ° C for 30 minutes, the silicon wafer is treated with a gas introducing port and an exhaust passage, and the rising of the process chamber hermetically closes the processing chamber, and the stage has a hot plate as a heating member. Place it on the stage of TVC-5002 (Tokyo Ohka Kogyo Co., Ltd.), which is a processing unit, raise the stage to close the processing chamber, and then depressurize the processing chamber to 26.6 Pa with an external vacuum decompression device, and set the stage temperature. The silica coating was irradiated with UV light having an illuminance of 20 mW / cm ² at a wavelength of 253.7 nm under the condition of 180 ° C. for 5 minutes. Next, this silicon wafer was heat-treated in nitrogen gas at 400 ° C. for 10 minutes. The silica-based coating thus obtained has an IR
As a result of the analysis, no OH group was observed in the film, and pinholes and cracks did not occur, and a uniform film was formed.
Further, in order to check the compactness, the silica-based coating was dipped in a 0.25 wt% HF aqueous solution at 25 ° C. for 3 minutes, and the amount of film slippage was measured from the change in film thickness before and after that, and the results are shown in the table.

Example 2 OCDTYPE, which is a coating liquid for forming a silica-based film, which contains a hydrolyzate of an alkoxysilane and contains 14.9% by weight of Al ₂ O _{3 based} on SiO ₂ calculated from the alkoxysilane.
-7 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) and the silica-based coating obtained by performing the same operation as in Example 1 except that the pressure inside the processing chamber was reduced to 1333 Pa, the presence of OH groups was not recognized by IR analysis, and pinholes were not observed. A uniform film was formed without the occurrence of cracks or cracks. Further, the results of examining the amount of film slip in the same manner as in Example 1 are shown in the table.

Example 3 OCD Type-2 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), which is a coating liquid for forming a silica-based coating film containing a hydrolyzate of a halogenated silane, was used, and the treatment chamber was set to 1333 Pa under the conditions of a stage temperature of 100 ° C. The silica-based coating film obtained by performing the same operation as in Example 1 except that the pressure was reduced did not show the presence of OH groups by IR analysis, and did not generate pinholes or cracks, and a uniform coating film was formed. Further, the results of examining the amount of film slip in the same manner as in Example 1 are shown in the table.

Comparative Examples 1 to 3 In Examples 1 to 3, obtained by subjecting the silica-based coating to heat treatment at 400 ° C. for 30 minutes in a nitrogen gas atmosphere without UV irradiation treatment under reduced pressure in a UV treatment device. The results of examining the amount of film slippage of the silica-based coating film in the same manner as in Example 1 are shown in the table.

From this table, it was confirmed that the silica-based coating film obtained by the method of the present invention was excellent in denseness.

(Effect of the Invention) According to the method for improving the quality of a silica-based coating film of the present invention, by irradiating the silica-based coating film with ultraviolet rays under reduced pressure, the silica-based coating film has a high degree of denseness and is uniform with no pinholes or cracks. Since a silica-based coating can be obtained, it is useful in fields requiring mechanical strength, chemical resistance and moisture resistance.

[Brief description of drawings]

The drawing shows an example of an apparatus used for carrying out the method of the present invention. In the drawing, 3 is a chamber, 4 is an ultraviolet ray generating lamp,
Reference numeral 6 is a gas inlet, 10 is a silica coating, and W is a substrate.

Front page continued (72) Inventor Akira Hashimoto 2-551 Kuriki, Isogo-ku, Yokohama, Kanagawa Prefecture (72) Toshihiro Nishimura 5-19-4 Oda, Kawasaki-ku, Kanagawa Prefecture

Claims (1)

[Claims] 1. A method for improving the quality of a silica-based coating, which comprises irradiating the silica-based coating with ultraviolet rays under reduced pressure.