JP2006096813A - Silica base film-forming coating liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silica base film-forming coating liquid which can fill a micro space with no generated void. <P>SOLUTION: The silica base film-forming coating liquid comprises a siloxane polymer and a solvent, wherein the solvent contains n-butanol and methyl 3-methoxypropionate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a coating liquid for forming a silica-based film.

  Conventionally, silica-based coatings by the SOG (spin on glass) method are often used as planarization films and interlayer insulating films used in the manufacture of substrates for semiconductor elements and liquid crystal elements. This method is a method of forming a silica-based film by applying a coating solution obtained by dissolving alkoxysilane in a solvent to cause a hydrolysis reaction on a substrate and then heat-treating it.

Various proposals have been made regarding coating solutions (silica-based coating forming coating solutions) for forming a silica-based coating by the SOG method (for example, Patent Documents 1, 2, and 3 below).
JP 2001-131479 A JP 2001-115029 A JP 2004-96076 A

In recent years, in the field of semiconductor elements and liquid crystal elements, in order to meet the demands for higher integration, higher speed, more functions, etc., the miniaturization of patterns formed on a substrate is rapidly progressing. For this reason, in the flattening film and the interlayer insulating film, it is required to fill a narrower space without voids, but it is difficult to meet such a request with a conventional coating liquid for forming a silica-based film.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a coating solution for forming a silica-based film that can embed a minute space without voids.

  In order to achieve the above object, the silica-based film forming coating solution of the present invention is a silica-based film forming coating solution containing a siloxane polymer and a solvent, wherein the solvent includes n-butanol and methyl-3-methoxy. It contains propionate.

  According to the present invention, it is possible to obtain a coating solution for forming a silica-based film that is excellent in embedding property and can form a silica-based film by filling a minute space without voids.

  As the siloxane polymer contained in the coating solution for forming a silica-based film of the present invention, those known as a material for forming a silica-based film by the SOG method can be appropriately used. Preferably, a reaction product obtained by hydrolyzing at least one selected from silane compounds represented by the following general formula (I) is used.

R _4-n Si (OR ′) _n (I)
In general formula (I), R represents a hydrogen atom, an alkyl group or a phenyl group, R ′ represents an alkyl group or a phenyl group, and n represents an integer of 2 to 4. When a plurality of R are bonded to Si, the plurality of R may be the same or different. The plurality of (OR ′) groups bonded to Si may be the same or different.
The alkyl group as R is preferably a linear or branched alkyl group having 1 to 20 carbon atoms, and more preferably a linear or branched alkyl group having 1 to 4 carbon atoms.
The alkyl group as R ′ is preferably a linear or branched alkyl group having 1 to 5 carbon atoms. The alkyl group as R ′ preferably has 1 or 2 carbon atoms from the viewpoint of hydrolysis rate.

The reaction product obtained by hydrolyzing the silane compound includes a low molecular weight hydrolyzate and a condensate (siloxane oligomer) produced by causing a dehydration condensation reaction between molecules simultaneously with the hydrolysis reaction. Can be. When the siloxane polymer in the present invention includes such a hydrolyzate or condensate, it refers to the whole including these.
The mass average molecular weight (Mw) (polystyrene conversion standard by gel permeation chromatography, the same shall apply hereinafter) of the siloxane polymer contained in the coating solution for forming a silica-based film of the present invention is preferably 1000 to 3000. A more preferable range is 1200 to 2700, and a further preferable range is 1500 to 2000. When the Mw of the siloxane polymer is at least the lower limit of the above range, good film forming ability is obtained, and when the Mw is at most the upper limit of the above range, good embedding and flatness are obtained.

The silane compound (i) when n in the general formula (I) is 4 is represented by the following general formula (II).
Si (OR ¹ ) _a (OR ² ) _b (OR ³ ) _c (OR ⁴ ) _d (II)
In the formula, R ¹ , R ² , R ³ and R ⁴ each independently represent the same alkyl group or phenyl group as the above R ′.
a, b, c and d are integers satisfying the condition of 0 ≦ a ≦ 4, 0 ≦ b ≦ 4, 0 ≦ c ≦ 4, 0 ≦ d ≦ 4 and a + b + c + d = 4.

The silane compound (ii) when n in the general formula (I) is 3 is represented by the following general formula (III).
R ⁵ Si (OR ⁶ ) _e (OR ⁷ ) _f (OR ⁸ ) _g (III)
Wherein, R ⁵ represents a hydrogen atom, the same alkyl groups as the R or a phenyl group. R ⁶ , R ⁷ , and R ⁸ each independently represent the same alkyl group or phenyl group as R ′ described above.
e, f, and g are integers that satisfy 0 ≦ e ≦ 3, 0 ≦ f ≦ 3, 0 ≦ g ≦ 3, and satisfy the condition of e + f + g = 3.

The silane compound (iii) when n in the general formula (I) is 2 is represented by the following general formula (IV).
R ⁹ R ¹⁰ Si (OR ¹¹ ) _h (OR ¹² ) _i (IV)
In the formula, R ⁹ and R ^{10 each} represent a hydrogen atom, the same alkyl group as R, or a phenyl group. R ¹¹ and R ¹² each independently represents the same alkyl group or phenyl group as the above R ′.
h and i are integers that satisfy 0 ≦ h ≦ 2, 0 ≦ i ≦ 2, and satisfy the condition of h + i = 2.

  Specific examples of the silane compound (i) include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetrapentyloxysilane, tetraphenyloxysilane, trimethoxymonoethoxysilane, dimethoxydiethoxysilane, and triethoxy. Monomethoxysilane, trimethoxymonopropoxysilane, monomethoxytributoxysilane, monomethoxytripentyloxysilane, monomethoxytriphenyloxysilane, dimethoxydipropoxysilane, tripropoxymonomethoxysilane, trimethoxymonobutoxysilane, dimethoxydibutoxy Silane, triethoxymonopropoxysilane, diethoxydipropoxysilane, tributoxymonopropoxysilane, dimethoxymonoethoxymonobutyl Xysilane, diethoxymonomethoxymonobutoxysilane, diethoxymonopropoxymonobutoxysilane, dipropoxymonomethoxymonoethoxysilane, dipropoxymonomethoxymonobutoxysilane, dipropoxymonoethoxymonobutoxysilane, dibutoxymonomethoxymonoethoxysilane, Examples thereof include tetraalkoxysilanes such as dibutoxymonoethoxymonopropoxysilane and monomethoxymonoethoxymonopropoxymonobutoxysilane, among which tetramethoxysilane and tetraethoxysilane are preferable.

  Specific examples of the silane compound (ii) include trimethoxysilane, triethoxysilane, tripropoxysilane, tripentyloxysilane, triphenyloxysilane, dimethoxymonoethoxysilane, diethoxymonomethoxysilane, dipropoxymonomethoxysilane, Dipropoxymonoethoxysilane, dipentyloxylmonomethoxysilane, dipentyloxymonoethoxysilane, dipentyloxymonopropoxysilane, diphenyloxylmonomethoxysilane, diphenyloxymonoethoxysilane, diphenyloxymonopropoxysilane, methoxyethoxypropoxysilane, monopropoxydimethoxy Silane, monopropoxydiethoxysilane, monobutoxydimethoxysilane, monopentyloxydiethoxysilane, Phenyloxydiethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltripentyloxysilane, ethyltrimethoxysilane, ethyltripropoxysilane, ethyltripentyloxysilane, ethyltriphenyloxysilane, propyl Trimethoxysilane, propyltriethoxysilane, propyltripentyloxysilane, propyltriphenyloxysilane, butyltrimethoxysilane, butyltriethoxysilane, butyltripropoxysilane, butyltripentyloxysilane, butyltriphenyloxysilane, methylmono Methoxydiethoxysilane, ethylmonomethoxydiethoxysilane, propylmonomethoxydiethoxysilane, butylmonomethoxydiet Sisilane, methylmonomethoxydipropoxysilane, methylmonomethoxydipentyloxysilane, methylmonomethoxydiphenyloxysilane, ethylmonomethoxydipropoxysilane, ethylmonomethoxydipentyloxysilane, ethylmonomethoxydiphenyloxysilane, propylmonomethoxydipropoxysilane , Propylmonomethoxydipentyloxysilane, propylmonomethoxydiphenyloxysilane, butylmonomethoxydipropyloxysilane, butylmonomethoxydipentyloxysilane, butylmonomethoxydiphenyloxysilane, methylmethoxyethoxypropoxysilane, propylmethoxyethoxypropoxysilane, butyl Methoxyethoxypropoxysilane, methyl monomethoxymonoethoxy monobutoxy Examples include silane, ethyl monomethoxy monoethoxy monobutoxy silane, propyl monomethoxy monoethoxy monobutoxy silane, butyl monomethoxy monoethoxy monobutoxy silane, among which trimethoxy silane, triethoxy silane, methyl trimethoxy silane are preferable.

  Specific examples of the silane compound (iii) include dimethoxysilane, diethoxysilane, dipropoxysilane, dipentyloxysilane, diphenyloxysilane, methoxyethoxysilane, methoxypropoxysilane, methoxypentyloxysilane, methoxyphenyloxysilane, ethoxypropoxy. Silane, ethoxypentyloxysilane, ethoxyphenyloxysilane, methyldimethoxysilane, methylmethoxyethoxysilane, methyldiethoxysilane, methylmethoxypropoxysilane, methylmethoxypentyloxysilane, methylmethoxyphenyloxysilane, ethyldipropoxysilane, ethylmethoxy Propoxysilane, ethyldipentyloxysilane, ethyldiphenyloxysilane, propyldimethoxysilane, Propylmethoxyethoxysilane, propylethoxypropoxysilane, propyldiethoxysilane, propyldipentyloxysilane, propyldiphenyloxysilane, butyldimethoxysilane, butylmethoxyethoxysilane, butyldiethoxysilane, butylethoxypropoxysilane, butyldipropoxysilane , Butylmethyldipentyloxysilane, butylmethyldiphenyloxysilane, dimethyldimethoxysilane, dimethylmethoxyethoxysilane, dimethyldiethoxysilane, dimethyldipentyloxysilane, dimethyldiphenyloxysilane, dimethylethoxypropoxysilane, dimethyldipropoxysilane, diethyldimethoxysilane , Diethylmethoxypropoxysilane, diethyldiethoxysilane, die Luethoxypropoxysilane, dipropyldimethoxysilane, dipropyldiethoxysilane, dipropyldipentyloxysilane, dipropyldiphenyloxysilane, dibutyldimethoxysilane, dibutyldiethoxysilane, dibutyldipropoxysilane, dibutylmethoxypentyloxysilane, dibutyl Methoxyphenyloxysilane, methylethyldimethoxysilane, methylethyldiethoxysilane, methylethyldipropoxysilane, methylethyldipentyloxysilane, methylethyldiphenyloxysilane, methylpropyldimethoxysilane, methylpropyldiethoxysilane, methylbutyldimethoxysilane, Methylbutyldiethoxysilane, methylbutyldipropoxysilane, methylethylethoxypropoxysilane , Ethylpropyldimethoxysilane, ethylpropylmethoxyethoxysilane, dipropyldimethoxysilane, dipropylmethoxyethoxysilane, propylbutyldimethoxysilane, propylbutyldiethoxysilane, dibutylmethoxyethoxysilane, dibutylmethoxypropoxysilane, dibutylethoxypropoxysilane, etc. Among them, dimethoxysilane, diethoxysilane, methyldimethoxysilane, and methyldiethoxysilane are preferable.

The silane compound used to obtain the reaction product can be appropriately selected from the silane compounds (i) to (iii).
A more preferred combination is a combination of a silane compound (i) and a silane compound (ii). When the silane compound (i) and the silane compound (ii) are used, these silane compounds (i) are preferably used in a range of 5 to 90 mol% and the silane compound (ii) in a range of 95 to 10 mol%. More preferably, the silane compound (i) is 10 to 80 mol%, the silane compound (ii) is more preferably 90 to 20 mol%, the silane compound (i) is 15 to 75 mol%, and the silane compound (ii). Is more preferably in the range of 85 to 25 mol%. The silane compound (ii) is more preferably one in which R ⁵ in the general formula (III) is an alkyl group or a phenyl group, preferably an alkyl group.

  The reaction product is prepared by, for example, a method in which one or more selected from the silane compounds (i) to (iii) are hydrolyzed and condensed in the presence of an acid catalyst, water, and an organic solvent. Can do.

As the acid catalyst, either an organic acid or an inorganic acid can be used.
As the inorganic acid, sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid and the like can be used, among which phosphoric acid and nitric acid are preferable.
Examples of the organic acid include carboxylic acids such as formic acid, oxalic acid, fumaric acid, maleic acid, glacial acetic acid, acetic anhydride, propionic acid, and n-butyric acid, and organic acids having sulfur-containing acid residues. Examples of the organic acid having a sulfur-containing acid residue include organic sulfonic acids, and examples of esterified products thereof include organic sulfates and organic sulfites. Among these, organic sulfonic acids, for example, compounds represented by the following general formula (V) are particularly preferable.

R ¹³ -X (V)
(In the formula, R ¹³ is a hydrocarbon group which may have a substituent, and X is a sulfonic acid group.)

In the general formula (V), the hydrocarbon group as R ¹³ is preferably a hydrocarbon group having 1 to 20 carbon atoms. The hydrocarbon group may be saturated or unsaturated, or linear. , May be branched or cyclic.
When the hydrocarbon group of R ¹³ is cyclic, for example, an aromatic hydrocarbon group such as a phenyl group, a naphthyl group, and an anthryl group is preferable, and among them, a phenyl group is preferable. One or more hydrocarbon groups having 1 to 20 carbon atoms may be bonded to the aromatic ring in the aromatic hydrocarbon group as a substituent. The hydrocarbon group as a substituent on the aromatic ring may be saturated or unsaturated, and may be linear, branched or cyclic.
Further, the hydrocarbon group as R ¹³ may have one or more substituents, and examples of the substituent include halogen atoms such as fluorine atoms, sulfonic acid groups, carboxyl groups, hydroxyl groups, amino Group, cyano group and the like.
The organic sulfonic acid represented by the general formula (V) is particularly nonafluorobutanesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, dodecylbenzenesulfonic acid or a mixture thereof from the viewpoint of the effect of improving the shape of the lower part of the resist pattern. Etc. are preferable.

The acid catalyst acts as a catalyst when the silane compound is hydrolyzed in the presence of water. The amount of the acid catalyst used is 1 to 1000 ppm, particularly 5 to 800 ppm, in the reaction system of the hydrolysis reaction. It is good to prepare so that it may become the range of.
The amount of water added is determined according to the hydrolysis rate to be obtained because the hydrolysis rate of the siloxane polymer changes accordingly.
In this specification, the hydrolysis rate of the siloxane polymer refers to the number of water molecules relative to the number of alkoxy groups (in moles) in the silane compound present in the reaction system of the hydrolysis reaction for synthesizing the siloxane polymer ( The number of moles) (unit:%).
In the present invention, the hydrolysis rate of the siloxane polymer is preferably 50 to 200%, and more preferably 75 to 180%. By setting the hydrolysis rate to be equal to or higher than the lower limit of the above range, good film quality in the silica-based film can be stably obtained. By making it below the lower limit of the above range, the storage stability of the coating liquid for forming a silica-based film is improved.

Examples of the organic solvent in the reaction system of the hydrolysis reaction include monohydric alcohols such as methanol, ethanol, propanol, and n-butanol, and alkylcarboxylic acids such as methyl-3-methoxypropionate and ethyl-3-ethoxypropionate. Acid esters, ethylene glycol, diethylene glycol, propylene glycol, glycerin, trimethylolpropane, hexanetriol and other polyhydric alcohols, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether , Diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol mono Monoethers of polyhydric alcohols such as chill ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, or their monoacetates, such as methyl acetate, ethyl acetate, butyl acetate Esters, ketones such as acetone, methyl ethyl ketone, methyl isoamyl ketone, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, And polyhydric alcohols ethers which all alkyl-etherified hydroxyl of a polyhydric alcohol such as ethylene glycol methyl ethyl ether.
The said organic solvent may be used independently and may be used in combination of 2 or more type.

Since the coating liquid for forming a silica film of the present invention contains n-butanol and methyl-3-methoxypropionate as essential components as solvents, n-butanol and organic solvents in the reaction system for synthesizing the siloxane polymer are used. It is preferable to use a mixed solvent of methyl-3-methoxypropionate.
When a mixed solvent of n-butanol and methyl-3-methoxypropionate is used, these mass ratios (n-butanol / methyl-3-methoxypropionate) are preferably in the range of 20/80 to 80/20, A more preferable range is 30/70 to 70/30.
By making the mass ratio of n-butanol and methyl-3-methoxypropionate within the above-mentioned range, the effect of improving repelling during coating and improving the coating property and improving the embedding property, the formation of a silica-based film An effect of reducing the amount of organic gas generated sometimes and an effect of improving the temporal stability of the coating solution are obtained. In particular, when the amount of butanol is not less than the lower limit of the above range, defects such as repellency are less likely to occur during application. Moreover, the storage stability of a coating liquid becomes good by making the amount of methyl-3-methoxypropionate more than the lower limit of the said range.

  A siloxane polymer is obtained by performing a hydrolysis reaction in such a reaction system. The hydrolysis reaction is usually completed in about 5 to 100 hours, but in order to shorten the reaction time, it is preferable to heat in a temperature range not exceeding 80 ° C.

After completion of the reaction, a reaction solution containing the synthesized siloxane polymer and the organic solvent used for the reaction is obtained. The reaction solution can be used as it is as a coating solution for forming a silica-based film, but in order to adjust to a preferable solid content concentration, a solution diluted with a dilution solvent is used as a coating solution for forming a silica-based film. Is preferred.
Although in terms of SiO ₂ concentration of the silica-based film-forming coating liquid of the present invention is not particularly limited, but it is preferably about 1 to 30 wt%, more preferably about 5 to 25 wt%.

The dilution solvent is preferably selected from those listed above as the organic solvent in the hydrolysis reaction, but other common organic solvents can also be used. A more preferable dilution solvent is a mixed solvent of the above n-butanol and methyl-3-methoxypropionate.
The solvent in the coating solution for forming a silica-based film may contain a solvent other than n-butanol and methyl-3-methoxypropionate as long as the effects of the present invention are not impaired. And the total content of methyl-3-methoxypropionate is preferably 50% by mass or more, more preferably 80% by mass or more, and still more preferably, of the solvent in the coating solution for forming a silica-based film. 98% or more, and 100% by mass is most preferable.

The silica-based coating-forming coating solution containing the reaction solution contains alcohol produced by the hydrolysis reaction of the silane compound. If the alcohol is excessively mixed, it may be removed by distillation under reduced pressure. The vacuum distillation has a degree of vacuum of 39.9 × 10 ^{2 to} 39.9 × 10 ³ Pa, preferably 66.5 × 10 ^{2 to} 26.6 × 10 ³ Pa, and a temperature of 20 to 50 ° C. within a range of 2 to 6 hours. It is better to do it.

  The coating liquid for forming a silica-based film of the present invention is suitably used for forming a silica-based film as a planarizing film or an interlayer insulating film. As a method of forming a silica-based film using the coating liquid for forming a silica-based film of the present invention, a normal SOG method can be used.

For example, first, a coating film is formed by applying a coating solution for forming a silica-based film on a substrate by a coating method such as spin coating, cast coating, or roll coating so as to have a predetermined film thickness. The thickness of the coating film is appropriately selected depending on the type of substrate to be applied.
It is then baked on a hot plate. The baking temperature at this time is about 80-500 degreeC, for example, More preferably, it is about 80-300 degreeC. Usually, the time required for this baking is 10 to 360 seconds, preferably 90 to 210 seconds. The baking process may be performed in a plurality of stages while changing the baking temperature.
Then, a silica-type film is obtained by baking at high temperature. The firing temperature is usually 350 ° C. or higher, preferably about 350 to 450 ° C.

The coating solution for forming a silica-based film of the present invention is excellent in embedding ability to fill a space between irregularities on the surface of a substrate without a gap, and can form a good silica-based film as a planarizing film or an interlayer insulating film.
For example, as shown in Examples described later, it is possible to achieve excellent embeddability such that a line and space pattern (1: 1) having a width of 0.1 μm can be embedded without voids.

Example 1
367.7 g (2.7 mol) of methyltrimethoxysilane, 411.0 g (2.7 mol) of tetramethoxysilane, 690.5 g of n-butanol and 690.5 g of methyl-3-methoxypropionate were mixed and stirred. . Thereto was added 340.2 g (19.0 mol) of water and 58.9 μL of nitric acid having a concentration of 60% by mass, and the mixture was further stirred for 3 hours to cause a hydrolysis reaction. The hydrolysis rate is about 100%.
Then, the reaction solution containing a siloxane polymer was obtained by making it react at 26 degreeC for 2 days. The mass average molecular weight (Mw) of the siloxane polymer in the reaction solution was 1559.
N-butanol 388.8g and methyl-3-methoxypropionate 388.8g were mixed with the said reaction solution 2415.2g as a diluent solvent, and the coating liquid for silica type film formation was obtained.

(Evaluation of embeddability)
A substrate on which a 0.1 μm 1: 1 line and space pattern was formed on a silicon wafer was prepared.
The silica-based coating-forming coating solution obtained above was applied onto the substrate by spin coating, and baked on a hot plate. The heating conditions in the baking treatment were multi-stage baking at 80 ° C. for 1 minute, then at 150 ° C. for 1 minute, and then at 200 ° C. for 1 minute. Then, it baked at 400 degreeC in the air, and obtained the silica-type film.
When the cross section of the obtained silica-based film was observed with an SEM (scanning electron microscope), no void was generated in the space between the patterns, there was no imbedding defect, and the embedding property was good.

(Example 2)
In the said Example 1, the hydrolysis rate was changed and the coating liquid for silica type film formation was prepared.
That is, 176.8 g (1.3 mol) of methyltrimethoxysilane, 197.6 g (1.3 mol) of tetramethoxysilane, 249.0 g of n-butanol, and 249.0 g of methyl-3-methoxypropionate were mixed. Stir. Thereto was added 327.6 g (18.3 mol) of water and 28.3 μL of nitric acid having a concentration of 60% by mass, and the mixture was further stirred for 3 hours to cause a hydrolysis reaction. The hydrolysis rate is about 200%.
Then, the reaction solution containing a siloxane polymer was obtained by making it react at 26 degreeC for 2 days. The mass average molecular weight (Mw) of the siloxane polymer in the reaction solution was 1741.
150 g of the reaction solution was mixed with 24.8 g of n-butanol and 24.8 g of methyl-3-methoxypropionate as dilution solvents to obtain a coating solution for forming a silica-based film.

  With respect to the obtained coating solution for forming a silica-based film, the embedding property was evaluated in the same manner as in Example 1. As a result, no void was generated in the space between patterns, there was no embedding failure, and the embedding property was good. there were.

(Comparative Example 1)
In Example 2, a coating solution for forming a silica-based film was prepared by using acetone and isopropyl alcohol (IPA) instead of n-butanol and methyl-3-methoxypropionate.
The hydrolysis rate in the hydrolysis reaction is about 200%. The mass average molecular weight (Mw) of the siloxane polymer in the reaction solution was 1956.

When the embedding property of the obtained coating solution for forming a silica-based film was evaluated in the same manner as in Example 1, a small amount of voids was observed in the space between patterns, and the embedding property in a fine pattern was inferior.

Claims (5)

In a coating solution for forming a silica-based film containing a siloxane polymer and a solvent,
The said solvent contains n-butanol and methyl-3-methoxypropionate, The coating liquid for silica type film formation characterized by the above-mentioned.   2. The coating liquid for forming a silica-based film according to claim 1, wherein the mass ratio of n-butanol and methyl-3-methoxypropionate is 20/80 to 80/20. The siloxane polymer has the following general formula (I)
R _4-n Si (OR ′) _n (I)
(In the formula, R represents a hydrogen atom, an alkyl group or a phenyl group, R ′ represents an alkyl group or a phenyl group, and n represents an integer of 2 to 4.)
The coating solution for forming a silica-based film according to claim 1, wherein the coating solution is a reaction product obtained by hydrolyzing at least one selected from the silane compounds represented by formula (1).   The silica-based film-forming coating solution according to any one of claims 1 to 3, wherein the siloxane polymer has a mass average molecular weight of 1000 to 3000. The said siloxane polymer is 50 to 200% of hydrolysis rate, The coating liquid for silica-type film formation of any one of Claims 1-4 characterized by the above-mentioned.