JPH09324052A - Production of silicon resin, silicon resin and coating liquid for forming insulation film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a silicon resin which can give films having reduce shrinkage and improved cracking resistance by bringing a specified trialkoxysilane compound, an inorganic acid and a carboxylic acid into contact with each other in the absence of water. SOLUTION: A trialkoxysilane compound represented by the formula (wherein X is H or F; and R<1> to R<3> are each a 1-4C alkyl) is mixed with optionally a tetraalkoxysilane compound represented by formula II (wherein R<4> to R<7> are each a 1-4C alkyl) in a molar ratio of 1/1 or smaller to obtain an alkyxysilane mixture. This mixture is mixed with 0.0005-0.01 equivalent of an inorganic avid and 0.3-3.0 equivalents of a carboxylic acid, and the resulting mixture is condensed at 10-100 deg.C for 0.5-120hr in the absence of water to obtain a silicon resin having a weight-average molecular weight of 2,000-300,000 (as measured by GPC and expressed in terms of the polystyrene).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a silicon resin, a silicon resin and a coating liquid for forming an insulating film. More specifically, the present invention is a method for producing a silicon resin that is subjected to a condensation reaction by contacting one or more trialkoxysilane compounds with an inorganic acid and a carboxylic acid, and does not use water during production. The obtained silicon resin does not undergo recondensation due to residual water during storage and does not undergo hydrolysis of Si-H bond or Si-F bond, and thus has excellent storage stability and insulation containing the silicon resin as a resin component. Since the coating liquid for film formation can stably hold Si—H bond or Si—F bond in the resin, shrinkage during film formation is small, crack resistance is excellent, and film thickness is 1.0 μm or more. The present invention relates to a method for producing a silicon resin having an excellent feature that an insulating film can be formed, a silicon resin obtained by the production method, and an insulating film forming coating liquid containing the silicon resin as a resin component. Is shall. Here, the insulating film forming coating liquid is an insulating film forming coating liquid for forming a protective film or an interlayer insulating film by coating various base materials including an electronic device with a soluble silicon resin.

[0002]

2. Description of the Related Art In the manufacture of VLSIs, etc., multilevel wiring technology is indispensable in accompaniment with higher accumulation and more functions, and there is a step on the substrate when forming the wiring pattern and insulating film in the manufacturing process. Technology is being emphasized. As this flattening method, a spin-on-glass method (SOG method) is generally put to practical use. This uses a silicon resin soluble in an organic solvent, which is applied to the surface of the substrate by spin coating,
This is a method of filling an indented portion of a step and performing a heat treatment to form an insulating film and planarize it.

The silicon resin is a resin obtained by hydrolyzing a silane compound having no organic group directly on silicon, such as an alkoxysilane such as tetraethoxysilane or triethoxysilane, or a halogenated silane such as trichlorosilane, in the presence of an acid catalyst. Since the insulating film is completely inorganic, the characteristics are highly reliable, and many studies have been conducted so far. For example, Japanese Patent Application Laid-Open No. 4-216827 discloses "Formula HSi (OR) ₃
(Wherein each R is an independent organic group that becomes a substituent that can be hydrolyzed when bonded to silicon through an oxygen atom) is a method of hydrolyzing a hydridosilane to produce a soluble resinous hydrolyzate. A mixture of components comprising a hydridosilane, an oxygen-containing polar organic solvent, water and an acid is made, and hydrolysis of the hydridosilane in the mixture for a time sufficient to hydrolyze or partially hydrolyze the hydridosilane. A method for hydrolyzing a hydridosilane comprising a step of promoting decomposition "is disclosed, and JP-A-7-97448 discloses" a method for producing a soluble cohydrolyzate from a cohydrolyzable silane. " And HSi (OR) ₃ and Si
(OR) ₄ is a mixture of silanes represented by the formula:
A silane mixture in which the molar ratio of i (OR) ₃ to Si (OR) ₄ is less than 3: 1 and each R is an independent organic group which becomes a hydrolyzable substituent when bonded to silicon through an oxygen atom. And a cohydrolyzate that forms a mixture of components comprising an oxygen-containing polar organic solvent, water and an acid, and then accelerates the hydrolysis of the silane in the mixture for a time sufficient to form the cohydrolyzate. Manufacturing method ”. However, since these methods use hydrolysis in polymerization, water is likely to remain in the product, and the unreacted alkoxy group remaining in the resin is gradually decomposed to cause condensation even during product storage. It has been difficult to obtain a product having good storage stability because it is accelerated, the molecular weight is increased, and finally gelation occurs. As a method for dehydrating the product, for example, a method of adding zeolite or the like can be considered, but it is not suitable for semiconductor device manufacturing use because inorganic ions such as sodium ions are mixed in the product.

[0004]

Under such circumstances, the problem to be solved by the present invention is that silicon which is subjected to a condensation reaction by contacting one or more trialkoxysilane compounds with an inorganic acid and a carboxylic acid. Since the method for producing a resin does not use water during production, the obtained silicon resin does not undergo recondensation during storage due to residual water and does not undergo hydrolysis of Si-H bond or Si-F bond. The coating liquid for forming an insulating film, which is excellent in stability and contains the silicon resin as a resin component, can stably hold Si-H bond or Si-F bond in the resin, and thus the shrinkage during film formation is small, A method for producing a silicon resin having excellent crack resistance and capable of forming a dense insulating film having a thickness of 1.0 μm or more, a silicon resin obtained by the method, and The fluororesin in which resides in providing an insulating film-forming coating liquid containing a resin component.

The wet etch rate at room temperature with dilute hydrofluoric acid is often used as an index of the film density. A thermal oxide film obtained by oxidizing a wafer as a very dense insulating film at about 1000 ° C. usually has a wet etch rate of several tens of angstroms / minute at room temperature when 0.5% hydrofluoric acid is used. Further, the coating insulating film that is often used has a thickness of several hundred to 1000 angstroms / minute under the same conditions.

Depending on the type of electronic device, there is a step of partially etching the insulating film formed at the time of manufacturing, so that an insulating film having a wet etching rate that can be controlled during etching is desired. 0.5% by weight
With an insulating film having a low wet etch rate with hydrofluoric acid, the wet etch rate can be raised to an appropriate range by increasing the hydrofluoric acid concentration, but the wet etch rate with 0.5 wt% hydrofluoric acid is too high. With the insulating film, if the concentration of hydrofluoric acid is too low, almost no etching is possible. From this, the wet etch rate at room temperature when using 0.5 wt% hydrofluoric acid is 10 to 10.
It is desired that the coating liquid has a thickness of 00 angstroms / minute, and it is also a problem to be solved by the present invention to provide such a coating liquid for forming an insulating film.

[0007]

[Means for Solving the Problems] The first aspect of the present invention is to provide one or more trialkoxysilane compounds represented by the following general formula (1) with an inorganic acid and an inorganic acid in the absence of water. The present invention relates to a method for producing a silicon resin which is subjected to a condensation reaction by bringing it into contact with a carboxylic acid. X-Si- (OR < ¹ >) (OR < ² >) (OR < ³ >) (1) (X represents a hydrogen atom or a fluorine atom, R < ¹ > -R < ³ > represents the same or different C1-C4 alkyl group. )

The second invention of the present invention relates to a silicon resin obtained by the manufacturing method of the first invention.

Further, a third invention of the present invention relates to an insulating film forming coating solution containing the silicon resin of the second invention as a resin component.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The production method of the present invention comprises contacting one or more trialkoxysilane compounds represented by the following general formula (1) with an inorganic acid and a carboxylic acid in the absence of water. Is a method for producing a silicon resin subjected to a condensation reaction. X-Si- (OR < ¹ >) (OR < ² >) (OR < ³ >) (1) (X represents a hydrogen atom or a fluorine atom, R < ¹ > -R < ³ > represents the same or different C1-C4 alkyl group. )

Specific examples of the trialkoxysilane compound represented by the general formula (1) include trimethoxysilane, triethoxysilane, tripropoxysilane, tributoxysilane, monomethoxydiethoxysilane, monoethoxydimethoxysilane, and monoethoxysilane. Propoxydimethoxysilane, monopropoxydiethoxylane, monobutoxydiethoxylane, butoxyethoxymethoxysilane, fluorotrimethoxysilane, fluorotriethoxysilane,
Examples thereof include fluorotripropoxysilane, fluorotributoxysilane, and fluoromonomethoxydiethoxysilane. Among the trialkoxysilane compounds represented by the general formula (1), trialkoxysilane compounds in which X in the general formula (1) is a hydrogen atom, for example, trimethoxysilane, triethoxysilane, tripropoxysilane, tributoxysilane. Etc. are preferable, and particularly trimethoxylane and triethoxylane, which are industrially easily available, are preferable.

In the present invention, in addition to the trialkoxysilane compound represented by the general formula (1), a tetraalkoxysilane compound represented by the following general formula (2) may be present in the condensation reaction system. Si (OR ⁴ ) (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (2) (R ^{4 to} R ⁷ represent the same or different alkyl groups having 1 to 4 carbon atoms.)

Specific examples of the tetraalkoxysilane compound represented by the general formula (2) include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane,
Examples thereof include tetrabutoxylan, monomethoxytriethoxysilane, dimethoxydiethoxysilane, monoethoxytrimethoxysilane, monopropoxytriethoxysilane, and monobutoxytriethoxysilane. Of these, industrially available trimethoxysilane or triethoxysilane is preferable.

It is preferable that the ratio of the tetraalkoxysilane compound / trialkoxysilane compound used (molar ratio in the charging step) is 1/1 or less. If the ratio is too large, the degree of cross-linking of the resin becomes high, so that the insulating film becomes brittle and cracks are likely to occur.

Specific preferred examples of the inorganic acid of the present invention include sulfuric acid, nitric acid, fuming sulfuric acid and the like having a low water content, and sulfuric acid is particularly preferable.

The usual amount of the inorganic acid used is preferably 0.0005 to 0.01 equivalent with respect to the alkoxysilanes,
More preferably, it is 0.001 to 0.005 equivalent. If the amount used is too small, the rate of the condensation reaction may decrease significantly, while if the amount used is too large, it may be difficult to remove the inorganic acid after the reaction.

Specific examples of the carboxylic acid of the present invention include formic acid, acetic acid, propionic acid, butyric acid, lactic acid, 2-ethoxypropionic acid, monochloroacetic acid, trichloroacetic acid, cyanoacetic acid, trifluoroacetic acid, and the like. Of these, formic acid and acetic acid are preferred.

The usual amount of carboxylic acid used is preferably 0.3 to 3.0 equivalents, more preferably 0.8 to 2.0 equivalents, based on the alkoxysilanes. If the amount used is too small, the molecular weight may be low, while if the amount used is too large, the molecular weight may be remarkably high, and it may be difficult to dissolve in an organic solvent.

In the production method of the present invention, a condensation reaction is carried out by contacting one or more trialkoxysilane compounds represented by the following general formula (1) with an inorganic acid and a carboxylic acid in the absence of water. It is attached.

The usual reaction temperature for the condensation reaction is 10 to 100.
The reaction time is 0.5 ° C. and the usual reaction time is 0.5 to 120 hours, but the optimum value can be set depending on the type of alkoxysilane compound, the type of inorganic acid and the type of carboxylic acid. The order of preparation is also not particularly limited. To carry out the condensation reaction, the components of the present invention may be mixed and stirred. The condensation reaction produces an ester compound, which is eliminated.

The production method of the present invention is carried out in the absence of water, which achieves the object of the present invention.

As a preferred specific example of the production method of the present invention, a method of carrying out a condensation reaction by the following two steps can be mentioned.

First step: a step in which a trialkoxysilane compound is mixed with an inorganic acid and a carboxylic acid to carry out precondensation to obtain an oligomer having a polystyrene reduced weight average molecular weight of 300 to 1000 in GPC analysis. Second step: the first step A step of performing a condensation reaction by additionally adding a carboxylic acid to the oligomer obtained in step 1 to obtain a silicone resin

From the viewpoint of accelerating the reaction rate (polymerization rate), it is preferable to add the carboxylic acid in portions by repeating the second step a plurality of times.

After the condensation, it is preferable that the present inventors remove the added inorganic acid or carboxylic acid, if necessary, by subjecting it to a treatment with an ion exchange resin as disclosed in JP-A-6-9926.

The polystyrene-reduced weight average molecular weight of the obtained silicon resin in GPC analysis is 2000 to 3000.
It is preferably 00, more preferably 2000-
30,000. If the molecular weight is too small, the film shrinkage may be significantly increased in the preparation of the insulating film, while if the molecular weight is too large, the solubility may be lowered when the coating solution is prepared.

The insulating film-forming coating solution of the present invention is an insulating film-forming coating solution containing the above-mentioned silicon resin of the present invention as a resin component.

The organic solvent for preparing the insulating film coating liquid is not particularly limited, but examples thereof include alcohols such as methanol, ethanol, isopropanol, butanol, 2-ethoxyethanol, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, cyclohexanone, 2-heptanone, etc. Ketones, N, N-dimethylformamide, N, N-dimethylacetamide, N
-Amides such as methyl-2-pyrrolidone, esters such as ethyl acetate, butyl acetate, ethyl lactate and ethyl cellosolve, ethers such as dipropyl ether, dibutyl ether, tetrahydrofuran, diethoxyethane and dimethoxyethane, dichloromethane, Examples thereof include halogenated hydrocarbons such as trichloroethane, and hydrocarbons such as hexane, heptane, cyclohexane, toluene and xylene. These may be used alone or in combination of two or more. The organic solvent can be replaced with a desired organic solvent solution by a method such as adding the solvent to the reaction-completed mixture or the treatment liquid from which the inorganic acid / carboxylic acid has been removed, and then performing vacuum distillation.

The concentration for dissolving the silicon resin in the organic solvent is not particularly limited, but is preferably 1 to 50% by weight, particularly preferably 5 to 30% by weight. This can be selected depending on the type of the obtained silicon resin and the film thickness of the insulating film to be formed.

Further, additives such as an antioxidant may be mixed to the extent that the storage stability of the obtained insulating film coating liquid and the properties of the insulating film are not impaired.

As a method for forming an insulating film using the coating liquid for forming an insulating film of the present invention, first, the above coating liquid is applied by a spin coating method or a dipping method which is generally used, and then a solvent is dried by air drying or heating at a low temperature. After sufficient removal, 300 ℃
It is carried out by heating at the above temperature to decompose the unreacted alkoxy group and form a siloxane bond at this portion.

[0032]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

Example 1 14 g of triethoxylane (manufactured by Shin-Etsu Silicone Co., Ltd.) was charged into a 3-necked flask having an internal volume of 100 ml, and an acetic acid-sulfuric acid solution (50 g of acetic acid mixed with 0.1 ml of concentrated sulfuric acid) 4.9
g was added dropwise over about 10 minutes. Then, the internal temperature was raised to 55 ° C., and the mixture was stirred for 5 hours to obtain a solution containing an oligomer having a polystyrene reduced weight average molecular weight of 450 in GPC analysis. 0.8 ml of acetic acid was added to this, and the internal temperature was 55
The reaction was continued for another 2 hours at ℃. After cooling, mixed bed ion exchange resin MB-HP (made by Rohm and Haas) about 15 ml
The reaction mixture was passed through a column packed with to remove sulfuric acid and unreacted acetic acid. About 3 parts by weight of ethanol was added to the obtained solution, and the solvent was concentrated by an evaporator. The operation of adding ethanol and concentrating the solvent was repeated twice to remove the reaction by-product, ethyl acetate, to obtain 21.4 g of an ethanol solution of silicon resin. The resin solid content in the heating weight loss method was 17.3%. GP
The polystyrene-converted average molecular weight by C analysis (HLC-8120 type manufactured by Tosoh Corporation, analytical column: Shodex KF-802 manufactured by Showa Denko KK) was 8520. When this solution was aged at room temperature for 5 days, the molecular weight was 10200.
However, after that, it was stored in a refrigerator (5 ° C) for 20 days G
PC analysis was continued and molecular weight was traced, but no increase was observed. The obtained oxide film coating liquid was applied to a 4-inch wafer by a few ml spin coating method (Micasa Spinner 1H-360 type manufactured by Mikasa) to form a coating film. The film thickness (initial film thickness) was controlled by the rotation speed, and measured using a film thickness meter (Nanospec 210 type manufactured by Nanometric Co., Ltd.). After baking this wafer at 450 ° C. for 30 minutes, the presence or absence of cracks was visually observed with an optical microscope to determine the maximum film thickness without cracks, which was taken as crack resistance. The shrinkage ratio was calculated from (shrinkage ratio) = {(initial film thickness)-(film thickness after firing)} / (initial film thickness) × 100. The results are shown in Table 1.

Example 2 Example 1 except that the amount of acetic acid added in the second stage was changed to 1.7 ml.
The same reaction as described above was performed. As a product, 16.5 g of an ethanol solution of silicon resin was obtained. The resin solid content was 20.0%. The molecular weight immediately after the reaction was 11,200, which increased to 16500 after 11 days, but there was no change in the molecular weight after 20 days of refrigerated storage. Table 1 shows the crack resistance and the shrinkage ratio.

Example 3 10.5 g of triethoxysilane and 4.4 g of tetraethoxysilane (manufactured by Shin-Etsu Silicone Co., Ltd.) were charged into a three-necked flask having an internal volume of 100 ml (triethoxysilane / tetraethoxysilane molar ratio = 3/1), acetic acid-
Sulfuric acid solution (50 g of acetic acid mixed with 0.1 ml of concentrated sulfuric acid) 4.
9g was dripped over about 10 minutes. Then the internal temperature is 55 ℃
And stirred for 5 hours to obtain a solution containing an oligomer having a polystyrene reduced weight average molecular weight of 700 in GPC analysis. 0.6 ml of acetic acid was added to this, and the internal temperature was 5
The reaction was continued at 5 ° C. for 4 hours. After cooling, the same treatment as in Example 1 was performed, and the operation of adding butyl acetate and concentrating the solvent was repeated 3 times in the same manner as in Example 1 to remove the reaction by-products ethanol and ethyl acetate. After removal, 15.9 g of a butyl acetate solution of silicon resin was obtained. The resin solid content in the heating weight loss method was 10.3%, and the polystyrene reduced average molecular weight was 4,382. When this solution was aged at room temperature for 5 days, the molecular weight increased to 8500, but no particular increase in molecular weight was observed after 10 days of refrigerated storage. Table 1 shows the crack resistance and the shrinkage ratio.

Example 4 The same operation as in Example 3 except that the amounts of charged triethoxysilane and ethoxysilane were changed to 9.3 g and 5.9 g (triethoxylane / tetraethoxysilane molar ratio = 1/1), respectively. And butyl acetate solution of silicon resin 14.5
g was obtained. Resin solid content by heat loss method is 15.3%
And the polystyrene reduced average molecular weight was 5010. When this solution was aged at room temperature for 5 days, the molecular weight increased to 8200, but no particular increase in the molecular weight was observed in the subsequent 8 days. Table 1 shows the crack resistance and the shrinkage ratio.

Comparative Example 1 The charging conditions were as follows: 14 g of triethoxylane and 0.
The same operation as in Example 1 was performed except that the amount was changed to 51 g (triethoxysilane charged / ion-exchanged water = 3/1). The obtained silicon resin ethanol solution was 26.3 g, and the resin solid content in the heating weight loss method was 16.1%. GPC analysis polystyrene equivalent average molecular weight is 1125
When the solution was aged at room temperature for 3 days, the molecular weight increased to 22500, and gelation occurred on the 5th day of refrigerated storage.

[0038]

[Table 1]

Example 5 An ethanol solution of a silicon resin obtained in the same manner as in Example 1 was applied on a 4-inch wafer by spin coating. After drying at 100 ℃ on a hot plate, 45
Baking was performed at 0 ° C. for 30 minutes. The obtained wafer with an insulating film was immersed in an aqueous solution of 0.5% by weight of hydrofluoric acid at 23 ° C. for a predetermined time, immediately washed with ultrapure water, and then dried. When the etch rate was measured from the difference in oxide film thickness before and after immersion in the hydrofluoric acid aqueous solution, it was 350 Å / min.

Comparative Example 2 A coating solution containing a silicon resin obtained in the same manner as in Comparative Example 1 was applied onto a 4-inch wafer by spin coating. After drying at 100 ℃ on a hot plate, 45
A wafer with an insulating film, which was baked at 0 ° C. for 30 minutes and dried at 100 ° C. on a hot plate, was obtained. When the etch rate was measured by the same method as in Example 5, it was 3300 angstroms / minute, which was extremely large.

[0041]

As described above, according to the present invention, there is provided a method for producing a silicon resin which is subjected to a condensation reaction by bringing one or more trialkoxysilane compounds into contact with an inorganic acid and a carboxylic acid. Since water is not used, the obtained silicon resin does not undergo recondensation during storage due to residual water and hydrolysis of Si-H bond or Si-F bond does not occur. Since the insulating film-forming coating liquid contained as the resin component can stably hold Si-H bond or Si-F bond in the resin,
Silicon resin having excellent features that it is possible to form an insulating film which has a small shrinkage during film formation, is excellent in crack resistance, has a film thickness of 1.0 μm or more, and is dense and easy to control by wet etching. It was possible to provide the method for producing, the silicon resin obtained by the method, and the coating solution for forming an insulating film containing the silicon resin as a resin component.

Claims (12)

[Claims] 1. Production of a silicon resin which is subjected to a condensation reaction by contacting one or more trialkoxysilane compounds represented by the following general formula (1) with an inorganic acid and a carboxylic acid in the absence of water. Method. X-Si- (OR < ¹ >) (OR < ² >) (OR < ³ >) (1) (X represents a hydrogen atom or a fluorine atom, R < ¹ > -R < ³ > represents the same or different C1-C4 alkyl group. ) 2. The production method according to claim 1, wherein X is a hydrogen atom. 3. The production method according to claim 1, wherein the trialkoxysilane compound represented by the general formula (1) is trimethoxysilane or triethoxysilane. 4. The production method according to claim 1, wherein a tetraalkoxysilane compound represented by the following general formula (2) is present in the condensation reaction system in addition to the trialkoxysilane compound represented by the general formula (1). . Si (OR ⁴ ) (OR ⁵ ) (OR ⁶ ) (OR ⁷ ) (2) (R ^{4 to} R ⁷ represent the same or different alkyl groups having 1 to 4 carbon atoms.) 5. The method according to claim 4, wherein the tetraalkoxysilane compound represented by the general formula (2) is tetramethoxysilane or tetraethoxysilane. 6. The production method according to claim 4, wherein the amount ratio (molar ratio) of the tetraalkoxysilane compound / trialkoxysilane compound is 1/1 or less. 7. The method according to claim 1, wherein the carboxylic acid is formic acid or acetic acid. 8. The production method according to claim 1, wherein the condensation reaction is performed by the following two steps. First step: GPC is performed by pre-condensation by mixing a trialkoxysilane compound with an inorganic acid and a carboxylic acid.
Polystyrene conversion weight average molecular weight in analysis 300-
Step of making 1000 oligomers Second step: Step of obtaining a silicone resin by performing a condensation reaction by additionally adding a carboxylic acid to the oligomer obtained in the first step 9. The production method according to claim 1, wherein the polystyrene-reduced weight average molecular weight in the GPC analysis of the silicon resin is 2000 to 300,000. 10. A silicon resin obtained by the manufacturing method according to any one of claims 1 to 9. 11. An insulating film-forming coating liquid containing the silicon resin according to claim 10 as a resin component. 12. The insulating film after firing at 23.degree.
The etching rate with a 5 wt% hydrofluoric acid aqueous solution is 10 to 1
The coating liquid for forming an insulating film according to claim 11, which has a coating rate of 000 Å / min.