JPH05179202A - Coating solution for forming silica coating film - Google Patents

Abstract

PURPOSE:To provide a coating solution comprising the reaction product of an alkylsilicate condensate with a carboxylic acid and the hydrolytic product of a tetraalkoxysilane and used for forming silica coating films having excellent etching processing characteristics and not generating cracks. CONSTITUTION:A silica solution for forming coating film comprises (A) a silica condensation product and (B) a hydrolysis product in a ratio of 1/0.1 to 1/0.7, preferably 1/0.2 to 1/0.5, between the Si atom of the component A and the Si atom of the component B. The hydrolysis product is obtained by reacting A1: an alkoxysilicate condensate of formula I (R1 to R5 are alkyl, alkoxyalkyl; R6 is alkyl, alkoxyalkyl; m is an integer of >=2; n is an integer satisfied with 0<=n<m with A2: a 1-18C carboxylic acid in a rate of >=0.2 mole to the moles of an ienquality II (m+n is an average degree of condensation) per g atom of the Si of the component A1. The hydrolysis product B is obtained by mixing B1: 1 mole of a tetraalkoxysilane of formula III (R7 is alkyl, phenyl) with B2: >=2 moles of water in an organic solvent.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a coating liquid for forming a silica film. More specifically, the present invention relates to a coating liquid for forming a silica film, which is most suitable for forming an insulating film for semiconductors by a coating film method.

[0002]

2. Description of the Related Art As a method for forming an insulating film for a semiconductor, a vapor phase growth method and a coating film method are known. By the way, in recent years, the degree of integration of semiconductors has become more sophisticated, and along with this, the line width of wiring has become narrower and the gap between them has become narrower.
In order to realize a fine wiring pattern, it is necessary to form an insulating film having a flat surface on a substrate having complicated irregularities. However, the vapor phase growth method has a problem that it is difficult to form a uniform and flat film when it is used on a surface having irregularities. On the other hand, the coating film method is an excellent method since it can be applied to a surface having irregularities. The important characteristics required for the insulating film for semiconductor are excellent etching processing characteristics and crack generation characteristics. The etching processing characteristics are characteristics relating to the denseness of the film, and the film having poor denseness, in other words, the porous film is fragile, and the control during etching becomes ineffective because the etching progresses extremely rapidly, Precise etching becomes impossible. Further, in forming the insulating film, it is necessary to apply the coating liquid and then to bake, but the film thickness is 400 to flatten the surface irregularities and enhance the insulating property.
Even when the thickness is increased to about 0 angstrom or more, it is necessary that cracks do not occur during firing, that is, the crack generation characteristics are excellent. By the way, JP-A-6
Japanese Patent Publication No. 1-55164 discloses a method of using a silica-based condensate obtained by reacting a specific alkyl silicate condensate with a carboxylic acid. However, this method has a problem in that the etching processing characteristics are insufficient.

[0003]

In view of the present situation, the problem to be solved by the present invention is that it has excellent etching processing characteristics, and that cracks do not occur even when a thick film of about 4000 angstroms or more is generated. The present invention is to provide a coating liquid for forming a silica film, which is capable of obtaining an insulating film for a semiconductor, which is also excellent in the generation characteristics of

[0004]

The present inventors have arrived at the present invention as a result of extensive studies to solve the above problems. That is, the present invention relates to a coating liquid for forming a silica film, which comprises the following X component and Y component. Component X: With respect to the alkyl silicate condensate represented by the following general formula (A), carboxylic acid having 1 to 18 carbon atoms is 0.2 mol or more per gram atom of silicon in the alkyl silicate condensate and (2- ( <M + n> -1) / <m +
n>) a silica-based condensate obtained by reacting at a ratio of less than (where <m + n> represents an average degree of condensation) Y component: general formula Si (OR ₇ ) ₄ (here, R ₇ alkyl) Group or a phenyl group), a silica-based compound obtained by mixing 2 moles or more of water per 1 mole of tetraalkoxysilane in an organic solvent. (In the formula, R _{1 to} R ₅ are the same or different alkyl groups or alkoxyalkyl groups, R ₆ is an alkyl group, an alkoxy group or an alkoxyalkyl group, and m is an integer of 2 or more,
n represents an integer of 0 ≦ n <m. )

The details will be described below. The coating liquid for forming a silica film of the present invention comprises an X component and a Y component. The component X means that the carboxylic acid having 1 to 18 carbon atoms is 0.2 mol or more per 1 gram atom of silicon in the alkyl silicate condensate with respect to the alkyl silicate condensate represented by the general formula (A) and (2- (<M + n> -1) /
It is a silica-based condensate obtained by reacting at a ratio of <m + n>) mol (here, <m + n> represents an average condensation degree).

The alkyl silicate condensate represented by the general formula (A) is removed by hydrolyzing a tetraalkoxysilane monomer with water, or by hydrolyzing an alkoxychlorosilane monomer or a tetrachlorosilane monomer with water and then reacting with an alcohol. A method of carrying out a hydrogen chloride reaction, a tetraalkoxysilane monomer, obtained by a method of adding a smaller number of moles of a monoalkyltrialkoxysilane monomer and hydrolyzing the same, and further a commercially available alkylsilicate condensate,
It may be used as it is or after being further condensed. In addition, R
The carbon number of _{1 to} R ₆ is usually 1 to 18, preferably 1
-10, most preferably 1-6.

Specific examples of the monomer used for producing the above alkyl silicate condensate include monoalkoxysilanes such as methyltrimethoxysilane, ethyltriethoxysilane and propyltriethoxysilane; methyltrichlorosilane and ethyl. Examples thereof include monoalkylchlorosilanes such as trichlorosilane; tetraalkoxysilanes such as tetramethoxysilane and tetraethoxysilane; trialkoxychlorosilanes such as trimethoxychlorosilane and triethoxychlorosilane. In addition, you may mix and use 2 or more types of these compounds. The alkoxyalkyl group in the general formula (A) means a group represented by R'OR- (wherein R'and R are alkyl groups).

The carboxylic acid has 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, and most preferably 2 to 6 carbon atoms.
What is used. When a carbon number of 19 or more is used, cissing is likely to occur when applied to the surface of the substrate.
Specific examples include formic acid, acetic acid, acetic anhydride, propionic acid, valeric acid, caproic acid, caprylic acid, benzoic acid and acrylic acid.

The amount of the carboxylic acid to be reacted with the alkyl silicate condensate is 0.2 mol or more per (1) gram atom of silicon in the alkyl silicate condensate and (2-(<m +
n> -1) / <m + n>) less than mol (where <m + n
> Represents the average degree of condensation. ), Preferably (1.3-
(<M + n> -1) / <m + n>) to (1.8-(<m
+ N> -1) / <m + n>) mol. If the amount of carboxylic acid is excessive, cracks are likely to occur in the resulting insulating film for semiconductors, while if the amount of carboxylic acid is insufficient, it is difficult to obtain a uniform film.

The reaction between the alkyl silicate condensate and the carboxylic acid is carried out by mixing both components. In order to accelerate the progress of the reaction, it is preferable to heat or add as a catalyst for a strong acid such as hydrochloric acid, sulfuric acid, or a sulfonic acid compound. The reaction is preferably carried out without a solvent or in the presence of an organic solvent having no hydroxyl group. The preferred specific reaction method is as follows.

In the alkyl silicate condensate, a mixed solution of a carboxylic acid and a catalyst is added dropwise or mixed at one time,
While stirring, the reaction is carried out at room temperature for 4 to 5 hours to 5 days or under heating under reflux for 0.5 to 8 hours. The reaction time is inversely proportional to the amount of the catalyst, and the reaction is extremely fast when a large amount of a catalyst, for example, about 2 × 10 ⁻² mol times of silicon is added, while the reaction is slow at about 2 × 10 ⁻⁶ mol times or less. However, if a considerable amount of the strong acid that is the catalyst remains in the coating liquid,
It is not preferable to use a too large amount of catalyst because it corrodes the substrate and metals on the substrate. Thus, the X component of the present invention is obtained.

The Y component of the present invention means the general formula Si (O
R ₇ ) ₄ (wherein R ₇ represents an alkyl group or a phenyl group) is a silica-based compound obtained by mixing 2 moles or more of water per mole of tetraalkoxysilane in an organic solvent. Specific examples of the tetraalkoxysilane represented by the general formula Si (OR ₇ ) ₄ include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, and tetraphenoxysilane. The carbon number of R ₇ is usually 1-18, preferably 1-10, and most preferably 1-6.

The amount of water used is 2 mol or more, preferably 2 to 10 mol, and most preferably 2 to 6 mol, per 1 mol of tetraalkoxysilane. If the amount of water is too small, the denseness and chemical resistance of the obtained insulating film for a semiconductor will deteriorate. On the other hand, if the amount of water is too large, the storage stability of the obtained coating liquid may be decreased, and gel may be generated,
Not preferable.

As the organic solvent, for example, methanol,
Alcohols such as ethanol and isopropanol; esters such as methyl acetate and ethyl acetate; ketones such as acetone are used. By mixing tetraalkoxysilane and water in an organic solvent, the tetraalkoxysilane is hydrolyzed, and at the same time, decomposition products are condensed,
A silica-based compound that is the Y component of the present invention is obtained.

The coating liquid for forming a silica film of the present invention is obtained by mixing the X component and the Y component. When the X component is absent, the crack generation characteristics are inferior, while when the Y component is absent, the etching processing characteristics are inferior. The amount ratio of X component and Y component is X
In the ratio of silicon atoms in the component and silicon atoms in the Y component,
The range of 1 / 0.1 to 1 / 0.7 is preferable, and 1 / 0.2
~ 1 / 0.5 is more preferable. If the X component is too small,
When the film thickness is set to about 4000 angstroms or more, cracks may occur, while when the Y component is too small, the etching processing characteristics may be deteriorated, which is not preferable. In order to mix the X component and the Y component, for example, both components may be charged in a container that can be sealed and sufficiently mixed with a magnetic stirrer or a stirrer with a rotation motor.

The thus-obtained mixed solution is adjusted in concentration with an organic solvent, if necessary, and filtered through a filter to obtain a final product, a silica film-forming coating solution. As the organic solvent for adjusting the concentration, ethers such as ethyl cellosolve, isopropyl cellosolve and butyl cellosolve; esters such as ethyl acetate and butyl acetate; alcohols such as ethanol; ketones such as acetone are used.

In order to improve the film-forming property, a polymer compound such as polyvinyl acetate, polyvinyl formal, polyvinyl ether, polyethylene oxide, polypropylene glycol or ethyl cellulose may be added to the coating solution for forming a silica coating film of the present invention. Good. Further, in order to improve the film quality, boron compounds such as boron oxide, boric acid, and alkyl borate esters; phosphorus compounds such as phosphorus pentoxide, phosphoric acid, and alkyl phosphate esters; arsenic oxide, arsenic acid, alkyl arsenate esters, and the like. Arsenic compounds; antimony compounds such as antimony oxide, antimonic acid, and alkyl antimonate and mixtures thereof are contained in an amount of 1% by weight or more and 50% by weight or less, preferably 2% by weight or less, relative to SiO ₂ derived from silicon of the X component and the Y component. 10% by weight or more
You may add in the following ratios. The above compound is preferably used in a state of being dissolved in the coating liquid. The substrate to which the coating liquid for forming a silica film of the present invention is applied may be glass, metal, resin, ceramic or the like. As a coating method, a dipping method in which a substrate is immersed in a liquid and pulled up and the film thickness is changed by adjusting the pulling speed, or a spin coating method in which the substrate is rotated at a high speed for coating is used. After coating using these methods, the substrate is dried and then heated in the range of 350 ° C to 1000 ° C to obtain a dense and smooth silica coating. When the coating liquid for forming a silica film of the present invention is used, the thickness is 0.5 μm.
Since a silica film of m or more can be obtained at a relatively low temperature of about 350 ° C., it is possible to manufacture a semiconductor in which a high temperature process cannot be used and to coat a heat-resistant polymer ceramic molded body. Further, when treated at a high temperature, a film having excellent electrical and mechanical properties can be obtained.
The coating liquid for forming a silica coating film of the present invention having such excellent characteristics is particularly suitable for use as an interlayer insulating film or a surface protective film for multilayer wiring of electronic parts.

[0018]

EXAMPLES The present invention will now be described with reference to examples. Example 1 Commercially available alkyl silicate condensate (ethyl silicate 4
0, trade name ES-40, manufactured by Nippon Colcoat Co., Ltd .: R _{1 to} R ₅ in the general formula (A) are ethyl, R ₆ is ethoxy, n = 0, and the average degree of condensation is 4.63. Is. ) 100 g and acetic acid 28 g (acetic acid / Si (molar ratio) =
0.7), 0.14 g of 96% sulfuric acid is added, and the mixture is stirred at a temperature of 70 ° C. for 5 hours to obtain X.
The ingredients were obtained. The amount of silicon in the X component is 0.67 mol. Next, 100 g of tetraethoxysilane was added to 8 parts of ethanol.
It was dissolved in 0 g, and 52 g of water (H ₂ O / Si molar ratio =
6.0) and 0.13 g of nitric acid were added, and the mixture was reacted in a 500 ml flask under reflux for 2 hours to obtain a Y component. This Y
The amount of silicon in the component is 0.48 mol. Then 5
The components X and Y were charged in a 00 ml flask, stirred at room temperature for 30 minutes, diluted with butyl cellosolve, and filtered through a 0.2 μm filter to obtain a coating solution. The mixing ratio of the X component and the Y component was adjusted so that the ratio of the silicon and the Y component in the X component was 1 / 0.1. A coating film was formed by applying a spinner coating on a silicon wafer having a diameter of 3 inches using the above coating solution and baking the same at 450 ° C. for 30 minutes. The evaluation was performed as follows. With respect to the crack generation characteristics, an experiment was conducted by sequentially increasing the thickness of the coating film, and the minimum thickness at which cracks were generated was evaluated. The thickness of the coating film was adjusted by adjusting the degree of dilution with butyl cellosolve within the range of 10% to 20%. Regarding the etching processing characteristics, for the film without cracks,
It was evaluated by the etching rate with 0.5 wt% hydrofluoric acid (if it is too fast, the etching processing characteristics are poor). As a result, the minimum film thickness for cracking was 7,000 Å, and the etching rate was 8,000 Å /
It was a minute.

Examples 2 to 4 and Comparative Examples 1 to 2 As shown in Table 1, the same procedure as in Example 1 was performed except that the ratio of the X component and the Y component was changed. The results are shown in Table 1. In all of the examples according to the present invention, both the crack generation characteristics and the etching processing characteristics show satisfactory results. On the other hand, Comparative Example 1 in which the Y component was not used was inferior in etching processing characteristics, and Comparative Example 2 in which the X component was not used was inferior in crack generation characteristics.

[0020]

[Table 1] ------------------------------------------ Actual Example Comparative Example 1 2 3 4 1 2 Y component / X component mixture ratio * 1 1 / 0.1 1 / 0.2 1 / 0.4 1 / 0.7 0/1 1/0 Minimum film thickness for crack generation (× 100 Å) * 2 70 70 70 60 70 40 Etching rate (× 100 (Angstrom / min) * 3 80 27 27 20 170 3 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

* 1 Ratio based on the amount of silicon of each component * 2 The thicker the better * 3 If the speed is too fast, the etching process characteristics will be poor

[0022]

As described above, according to the present invention, cracks do not occur even when the etching processing characteristics are excellent and a thick film of about 4000 angstroms or more is formed.
It was possible to provide a coating liquid for forming a silica film, which is capable of obtaining an insulating film for a semiconductor, which is also excellent in crack generation characteristics.

Claims (2)

[Claims] 1. A coating liquid for forming a silica film, which comprises the following X component and Y component. Component X: With respect to the alkyl silicate condensate represented by the following general formula (A), carboxylic acid having 1 to 18 carbon atoms is 0.2 mol or more per gram atom of silicon in the alkyl silicate condensate and (2- ( <M + n> -1) / <m +
n>) a silica-based condensate obtained by reacting at a ratio of less than (where <m + n> represents an average degree of condensation) Y component: general formula Si (OR ₇ ) ₄ (here, R ₇ alkyl) Group or a phenyl group), a silica-based compound obtained by mixing 2 moles or more of water per 1 mole of tetraalkoxysilane in an organic solvent. (In the formula, R _{1 to} R ₅ are the same or different alkyl groups or alkoxyalkyl groups, R ₆ is an alkyl group, an alkoxy group or an alkoxyalkyl group, and m is an integer of 2 or more,
n represents an integer of 0 ≦ n <m. ) 2. The content ratio of the X component and the Y component is 1 / 0.1 / 1 / in the ratio of silicon in the X component and silicon in the Y component.
The coating liquid for forming a silica film according to claim 1, which is 0.7.