JPH0827421A - Composition for spin coating - Google Patents

Abstract

PURPOSE:To obtain a composition for spin coating, consisting essentially of a tetraalkoxysilane (a partial hydrolyzate), an organic solvent having a specific boiling point, water and an organic carboxylic acid, good in preservation stability and capable of providing a film having a flat surface without any striation. CONSTITUTION:This composition for spin coating consists essentially of (A) a tetraalkoxysilane (e.g. tetramethoxysilane) and/or its partial hydrolyzate, (B) an organic solvent having 110-170 deg.C boiling point (e.g. 2-ethoxyethanol), (C) water and (D) an organic carboxylic acid (e.g. maleic acid). The composition for the spin coating is obtained by mixing the tetraalkoxysilane (a partial hydrolyzate) with the organic solvent, stirring the resultant mixture at ambient temperature, uniformly dissolving the tetraalkoxysilane therein, then adding water and organic carboxylic acid thereto in the order, stirring the prepared mixture until the organic carboxylic acid is dissolved and subsequently allowing the resultant solution to stand at ambient temperature for 4 days. Thereby, the composition for the spin coating is good in preservation stability of the liquid and capable of providing a silica film having an extremely small dispersion in thickness and a flat surface without any striation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spin coating composition, which provides a silica coating having good storage stability of liquid, no striation, extremely small variation in thickness, and a flat surface.

[0002]

2. Description of the Related Art It has been practiced in various fields to form silica coatings on various substrates using various silicates as raw materials and a sol-gel method. There are several possible methods for coating silicate substrates, but among them, spin coating is a simple and effective coating process for forming thin films. Specifically, it is a multilayer wiring process in the field of VLSI manufacturing processes. It is generally used for forming a flattening insulating film for fine wiring steps corresponding to the above and a protective film on an optical disk substrate.

[0003]

However, in general, when a base material such as a silicon wafer or glass is applied by a spin coating method, and the film is baked at a high temperature to form a coating film, the film thickness distribution of the coating layer is Are generated radially from the center of rotation of the substrate, resulting in a striped pattern called striation. That is, if there is striation, the surface of the coating becomes uneven and has no flatness. If the film thickness is uneven and the film surface is uneven, the step coverage of the underlying wiring is insufficient in the insulating film of the LSI multilayer wiring process, and the unevenness is enlarged by further multilayering There is a problem of disconnection and short circuit. Further, in the optical disc substrate, there arises a problem that a concave defect remains on the disc surface.

[0004]

Therefore, as a result of diligent studies on these conventional problems, the present inventors have found that by using a composition consisting of specific components as a coating liquid for spin coating, the storage stability of the liquid can be improved. The inventors have found that a silica coating having good properties, no striations, extremely small variation in thickness, and having a flat surface can be obtained, and reached the present invention.

That is, the gist of the present invention is as follows. A tetraalkoxysilane and / or a partial hydrolyzate thereof, B. An organic solvent having a boiling point of 110 ° C. or higher and 170 ° C. or lower, C.I. Water, and D.I. A spin coating composition containing an organic carboxylic acid as an essential component.

The present invention will be described in detail below. The component A used in the present invention is usually tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane,
Tetraalkoxysilanes such as tetrabutoxysilane and / or their partial hydrolysates are used. As these silanes, any of tetraalkoxysilane monomers and oligomers of dimers or more obtained by partially hydrolyzing them may be used, and the monomers and oligomers may be used in combination. The hydrolysis reaction itself can be carried out by a known method, for example, by adding a predetermined amount of water to the tetramethoxysilane in the presence of an acid catalyst and distilling off by-produced methanol, usually the reaction is carried out at room temperature to 100 ° C. Let Methoxysilane is hydrolyzed by this reaction, and a liquid decomposition product having two or more hydroxyl groups in the molecule by the subsequent condensation reaction (average degree of polymerization 2 to 8,
Most are obtained as 3-7). The degree of hydrolysis is
Although it can be appropriately adjusted depending on the amount of water used, in the present invention, it is usually selected from about 20 to 80%, more preferably about 30 to 60%. Hydrolysis rate 100%
The term means that water is added in an amount necessary for hydrolytically condensing all the hydrolyzable groups of tetramethoxysilane, that is, 1/2 the number of moles of these groups.
The tetramethoxysilane oligomer thus obtained usually contains about 2 to 10% of a monomer. Since these monomers have low boiling points, they can be easily removed outside the system by boiling the oligomer, and thus they can be used as an oligomer substantially containing no monomer.

The B component of the present invention has a boiling point of 110 ° C. or higher 17
There is no particular limitation as long as it is an organic solvent having a temperature of 0 ° C. or lower, and more preferably 115 ° C. or higher and 160 ° C. or lower, as long as it can uniformly dissolve the component A alkoxysilane and its oligomer. Specifically, aliphatic alcohols such as 1-pentanol, 2-pentanol, 1-hexanol, butyl acetate, n-propyl propionate, ethyl n-butyrate, ethyl lactate, methyl valerate, is.
Esters such as o-ethyl valerate, 2-hexanone, 3
-Ketones such as hexanone and 2-heptanone, ether alcohols such as 2-methoxyethanol, 2-ethoxyethanol and 2-methoxypropanol, propylene glycol-1-methyl ether-2-acetate, 3
-Ethyl ester such as methyl methoxypropionate can be used, and two or more kinds of these solvents may be mixed and used. When the boiling point of these solvents is lower than 110 ° C., during spin coating, the volatilization of the solvent during the rotation of the substrate is too fast, so that the spreading property of the liquid on the substrate is deteriorated and a uniform film thickness is obtained. The coat becomes impossible. As a result, striation and non-uniformity of film thickness occur.
On the contrary, when a solvent having a boiling point higher than 170 ° C. is used, the solvent volatilizes slowly during the rotation of the substrate during spin coating. Therefore, the reaction rate of the sol-gel reaction of tetraalkoxysilane that progresses as the solvent volatilizes becomes extremely low, and only a film having a small film thickness can be obtained. Also,
Depending on the solubility of the components A, C and D, a low boiling point solvent such as methanol, ethanol or isopropyl alcohol may be mixed with the component B solvent. However, when these low boiling point solvents are used in combination, the amount is preferably 20 parts by weight or less with respect to 100 parts by weight of the component B. When the amount is more than 20 parts by weight, the solvent volatilizes quickly, and it is difficult to obtain a film having a uniform film thickness. A suitable amount of the component B to the component A is 50 to 100 parts by weight of the solvent for 100 parts by weight of the component A.
0 parts by weight is preferred. When the amount of solvent is less than 50 parts by weight,
When spin-coated, the spreadability of the liquid on the substrate is poor, and the difference in the thickness of the coating between the center and the periphery of rotation tends to become large. On the other hand, if the amount of the solvent is more than 1000 parts by weight, only a film having an extremely small thickness can be obtained, and if the film thickness is smaller than the desired film thickness, the need for further recoating tends to occur.

The water of the component C of the present invention is necessary for promoting the hydrolysis reaction of the alkoxy group remaining in the alkoxysilane of the component A. The required amount of water varies depending on the hydrolysis rate of the remaining alkoxy groups of the component A itself used as a raw material, but is preferably 0.5 times or more the amount of 100% equivalent of the hydrolysis rate. If the amount of water is small, not only the thickness of the film obtained by baking at high temperature after coating but also the film thickness may be extremely reduced, but also the flatness of the film surface may be significantly impaired.

Like the C component, the organic carboxylic acid of the D component is also a catalyst necessary for the progress of the hydrolysis reaction of the alkoxy group remaining in the alkoxysilane of the A component and the subsequent condensation / curing reaction. It is not particularly limited as long as it can be dissolved in an alcohol / water solvent, but specifically,
Maleic acid, oxalic acid, trichloroacetic acid, formic acid, succinic acid, acetic acid and the like can be mentioned, and the preferable addition amount is 0.3 part by weight or more based on 100 parts by weight of the alkoxysilane as the component A. When a film is formed from a composition in which the amount of component D is less than or equal to this amount, the thickness of the obtained film tends to be extremely small. The present invention is mainly composed of the above four components,
The compounding method is generally to dissolve tetraalkoxysilane in the above solvent at room temperature and then add water and an organic carboxylic acid.

The composition of the present invention thus obtained is formed into a film on a substrate such as a ceramic or a metal by a spin coating method, and then the solvent is volatilized and then heat-cured at 400 ° C. or higher to eliminate striation. In addition, it is possible to obtain a silica coating having a very small variation in thickness and a flat surface.

[0011]

The present invention will be described in more detail with reference to the following examples.

(Synthesis example) In a 500 ml four-necked round bottom flask equipped with a stirrer, a condenser for reflux and a thermometer, 234 g of tetramethoxysilane and 74 g of methanol were added.
Was added and mixed, 22.2 g of 0.05% hydrochloric acid was added, and a hydrolysis reaction was performed at a liquid temperature of 65 ° C. for 2 hours. Then, the condenser was replaced with an extraction tube, the temperature of the liquid was raised to 130 ° C., and the mixture was extracted with methanol for condensation.
Thus, Hydrolyzate A was obtained. The degree of polymerization was 2 to 8 and the number of hydroxyl groups in one molecule was 10 or more. The amount of monomers in this tetramethoxysilane oligomer was 5%. Subsequently, the tetramethoxysilane oligomer was put into a jacket heated to 130 ° C., the vaporized monomer was discharged to the outside of the system together with an inert gas, the temperature was raised to 150 ° C., the temperature was maintained for 3 hours, and the amount of the monomer was 0.2%. A certain tetramethoxysilane partial hydrolyzate B was obtained.

Example 1 62.1 g of 2-ethoxyethanol was partially hydrolyzed with tetramethoxysilane B3 obtained by the above synthesis example.
1.0 g was mixed and stirred at room temperature to dissolve uniformly.
To this, 6.6 g of water and 0.31 g of maleic acid were added in this order, and the mixture was further stirred until maleic acid was dissolved, and allowed to stand at room temperature for 4 days, resulting in a viscosity of 0.2 poi at room temperature.
A spin coating composition of se was obtained. This composition was dropped onto a silicon wafer substrate having a diameter of 5 inches to obtain 4000
Spin-coated at a rotation speed of rotation / minute. Immediately thereafter, the solvent was volatilized on a hot plate at 120 ° C. for 2 minutes, and then heat-cured in an oven at 450 ° C. for 30 minutes. The characteristics of the obtained film are shown in the table.

When nine points were arbitrarily selected from the obtained coated surface and the film thickness was measured with a film thickness meter Lambda Ace, the variation in the film thickness was extremely small and uniform. Also, there was no occurrence of striation. Further, when the flatness of the film surface was examined by a palpation type surface roughness tester Taristep, it was found to be flat.

Example 2 Tetramethoxysilane (manufactured by Colcoat Co., Ltd .: “Methyl silicate 3” was added to 49.0 g of 2 -ethoxyethanol.
9 ") 39.9 g were mixed and stirred at room temperature to uniformly dissolve. To this, 10.7 g of water and 0.40 g of maleic acid were added in this order, and the mixture was further stirred until maleic acid was dissolved, and then allowed to stand at room temperature for 4 days, so that the viscosity was 0.2 poise at room temperature for spin coating. A composition was obtained. This composition was spin-coated under the same conditions as in Example 1 and heat-cured to form a silica coating. The characteristics of the obtained film are shown in the table.

Example 3 62.1 g of 2-ethoxyethanol was mixed with 31.0 g of a partial hydrolyzate A containing a monomer of tetramethoxysilane, and the mixture was stirred at room temperature and uniformly dissolved. Water 6.
6 g and 0.31 g of maleic acid were added in this order, the mixture was further stirred until maleic acid was dissolved, and then left standing at room temperature for 4 days to obtain a spin coating composition having a viscosity of 0.2 poise at room temperature. . This composition was spin-coated under the same conditions as in Example 1 and heat-cured to form a silica coating. The characteristics of the obtained film are shown in the table.

Comparative Example 1 57.1 g of tetramethoxysilane (“Ethyl silicate 28” from Colcoat Co., Ltd.) was dissolved in 31.4 g of ethanol, and 11.2 g of water and 0.57 g of maleic acid were added thereafter. A solution was prepared under the same conditions as in the example to obtain a composition. A film was formed by spin coating and thermosetting under the same conditions as in the example. The characteristics of the obtained film are shown in the table.

Comparative Example 2 Tetramethoxysilane partial hydrolyzate A obtained by the above synthesis example was added to 62.1 g of N-methyl-2-pyrrolidone.
Was dissolved in 31.0 g of water, 6.52 g of water, and maleic acid 0.3
1 g was added and a solution was prepared under the same conditions as in Example to obtain a composition. A film was formed by spin coating and thermosetting under the same conditions as in the example. The characteristics of the obtained film are shown in the table.

Comparative Example 3 Under the same conditions as in Example 1 except that 33.3 g of tetramethoxysilane partial hydrolyzate A was dissolved in 66.7 g of 2-ethoxyethanol and 0.34 g of maleic acid was added without adding water. A solution was prepared to obtain a composition. A film was formed by spin coating and thermosetting under the same conditions as in the example. The characteristics of the obtained film are shown in the table.

Comparative Example 4 36.3 g of tetramethoxysilane partial hydrolyzate A was dissolved in 66.7 g of 2-ethoxyethanol, and water 7.06
After adding g, spin coating and thermosetting were performed under the same conditions as in Example except that maleic acid was not added to form a film. The characteristics of the obtained film are shown in the table.

Comparative Example 5 A composition was prepared under the same conditions as in Example except that the same amount of pyridine was used in place of maleic acid, and the solution became cloudy and gelled 4 days after mixing the four components, and the composition could not be spin-coated. It became a thing.

[0022]

[Table 1]

(1) Measured with an E-type viscometer at room temperature (2) Using a film thickness meter "Lambda Ace" (manufactured by Dainippon Screen Mfg. Co., Ltd.), arbitrarily select 9 points from the coating film on the substrate. Select and measure film thickness (3) Maximum value (or minimum value) of film thickness measurement data at 9 points
Value obtained by dividing the absolute value of the difference between the average value and the average value (4) Visual diagnosis (5) Palpation with the surface shape roughness meter "Taristep" (manufactured by Rank Paler Hogson Co., Ltd.)

As is apparent from the table, the composition of the present invention has good storage stability, and spin coating gives a coating having no striation and a uniform thickness and a flat surface.

[0025]

Industrial Applicability According to the present invention, it is possible to obtain a spin-coating composition having a good storage stability, a uniform film thickness without striation, and a flat surface.

Front page continuation (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G11B 7/24 537 A 7215-5D H01L 21/027

Claims (1)

[Claims] 1. A. First Embodiment A tetraalkoxysilane and / or a partial hydrolyzate thereof, B. An organic solvent having a boiling point of 110 ° C. or higher and 170 ° C. or lower, C.I. Water, and D.I. A composition for spin coating containing an organic carboxylic acid as an essential component.