JPH1129744A - Coating solution for formation of silica-based film, its preparation and silica-based film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating solution for formation of a silica-based film which forms a film having high storage stability, thick-film formability, crack resistance and surface smoothness, and a silica-based film with high crack resistance and surface smoothness the thickness, of which can be increased, and to provide its preparation method. SOLUTION: A coating solution for formation of a silica-based film comprises (A) a siloxane polymer obtained by allowing an alkoxysilane compound of the formula Rn Si(OR)4-n (wherein R is a 1-4C alkyl; (n) is an integer of from 0 to 2) to undergo hydrolysis and polycondensation, and (B) a hexaalkyldisiloxane compound of the formula R'3 Si-O-SiR'3 (wherein R' is a 1-4C alkyl). A silica-based film is formed by using this coating solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coating solution for forming a silica-based film, a method for producing the same, and a silica-based film. More specifically, the present invention relates to a silica-based film having excellent liquid stability even at a high concentration and good film-forming properties. The present invention relates to a coating solution for forming a silica-based film capable of adjusting a film, a method for producing the same, and a silica-based film.

[0002]

2. Description of the Related Art Conventionally, as a method of flattening an interlayer insulating film of a semiconductor element such as an IC or an LSI, SiO ₂ , SiN is formed on a substrate having a patterned wiring layer by a vapor deposition method such as vacuum deposition or CVD. The first layer of an interlayer insulating film is formed, and the second layer is spin-coated with an SOG solution (oligomer of organosiloxane), followed by heat treatment to form an organosiloxane-based film. Next, an SOG planarization process using a three-layer interlayer film in which a third interlayer insulating film is formed in the same manner as the first layer is widely used.

In recent years, there has been an increasing demand for multilayer wiring, and a demand for an improvement in a focus margin in a fine wiring processing process has led to a flattening technique that can replace a conventional flattening technique using a silica-based coating liquid. A new flattening technology that is excellent in lithography has become indispensable. In order to meet this demand, in recent years, SiO formed by a vapor phase growth method such as CVD has been used.
Planarization by the CMP method ₂ has been proposed. But,
There are problems such as improvement in throughput, reduction in cost, and establishment of a cleaning technique after polishing.

At present, in order to solve these problems, it is possible to improve the throughput by spin-coating a siloxane oligomer (SOG) on a substrate, curing it, and then flattening it by a CMP method. It is considered that the cost can be reduced. However, SO
In order to flatten the film made from G by the CMP method, for example, the flatness after polishing becomes insufficient unless the film thickness of the silica-based film is equal to or larger than the wiring step. When the wiring step is 1 μm or more, the coating liquid for forming a silica film must have a thick film forming property. In order to form a silica coating of 1 μm or more,
It is difficult to form a film having good film-forming properties and good applicability unless the resin component concentration of the silica-based film-forming coating solution is increased in addition to controlling the number of coating revolutions. However, when the concentration of the resin component is increased, there is a problem that the storage stability of the coating solution for forming a silica-based film decreases.

[0005]

SUMMARY OF THE INVENTION The first aspect of the present invention is to form a silica-based film capable of forming a film excellent in storage stability and thick film forming property, and excellent in crack resistance and surface smoothness. To provide a coating solution for use. Claim 2
The invention described in (1) provides a method for producing a coating solution for forming a silica-based film, which is capable of forming a film having excellent storage stability and thick film-forming properties, and excellent crack resistance and surface smoothness. . The third aspect of the present invention is to provide a silica-based coating which can increase the film thickness and is excellent in crack resistance and surface smoothness.

[0006]

According to the present invention, there is provided (A) a compound represented by the following general formula (I):

Embedded image (Wherein R is an alkyl group having 1 to 4 carbon atoms, n is an integer of 0 to 2, and a plurality of Rs may be the same or different), Siloxane polymer obtained by polycondensation and (B) general formula (II)

Embedded image (Wherein R ′ represents an alkyl group having 1 to 4 carbon atoms;
R's may be the same or different.) The present invention relates to a coating solution for forming a silica-based film, comprising a hexaalkyldisiloxane compound represented by the following formula:

Further, the present invention relates to (A) the above-mentioned general formula (I)
An aqueous solution of a siloxane polymer obtained by hydrolyzing and polycondensing an alkoxysilane compound represented by the formula (B):
The present invention relates to a method for producing a coating liquid for forming a silica-based film, which comprises mixing a hexaalkyldisiloxane compound represented by the general formula (II). The present invention also relates to a silica-based coating formed using the above-described coating liquid for forming a silica-based coating.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The alkoxysilane compound represented by the general formula (I) is specifically described below.

Embedded image Such as tetraalkoxysilane,

Embedded image Monoalkyl trialkoxysilane such as,

Embedded image And the like, and one or more of these may be used.

The alkoxysilane oligomer represented by the general formula (I) used in the present invention is not limited in the proportion of tetraalkoxysilane, monoalkyltrialkoxysilane and dialkyldialkoxysilane, but it has good silica coating. The dialkyldialkoxysilane is preferably used in an amount of 50 mol% or less based on the total amount of the alkoxysilane compound to be used.

[0010] The siloxane polymer in the present invention is produced by hydrolyzing and polycondensing the alkoxysilane compound represented by the above general formula (I). It is preferable to use inorganic acids such as nitric acid and hydrofluoric acid, and organic acids such as oxalic acid, maleic acid, sulfonic acid and formic acid, and basic catalysts such as ammonia and trimethylammonium.
These catalysts are used in an appropriate amount in accordance with the amount of the alkoxysilane compound represented by the general formula (I), and preferably from 0.001 to 1 mol per mol of the alkoxysilane compound represented by the general formula (I). It is used in a range of 0.5 mol.

The above-mentioned hydrolysis / polycondensation is preferably carried out without solvent. In this reaction, water is present. The amount of water is also determined as appropriate. However, if the amount is too small or too large, there is a problem that the storage stability of the coating solution is lowered. Therefore, the amount of water is determined by the alkoxysilane represented by the general formula (I). 0.5 to 1 mole of compound
It is preferably in the range of 4 to 4 mol. The hydrolysis / polycondensation product (alkoxysilane oligomer) obtained as described above is obtained as a solution using the alcohol produced by hydrolysis and the water remaining unreacted as a solvent, and this (reaction liquid) is used as it is. It can be used as an alkoxysilane oligomer liquid. Further, another solvent may be added to this, and the solvent may be once removed from the above reaction solution and used as an alkoxysilane oligomer. You may use as.

The hexaalkyldisiloxane compound represented by the general formula (II) used in the present invention is specifically described below.

Embedded image and so on.

The amount of the hexaalkyldisiloxane compound represented by the general formula (II) used in the present invention is determined by the amount of hydrolysis / polycondensate (alkoxysilane oligomer) of the alkoxysilane compound represented by the general formula (I). From the viewpoint of the storage stability of (1) and the film quality of the silica-based coating film, the ratio is preferably in the range of 1.8 mol to 2.8 mol with respect to 1 mol of the raw material alkoxysilane compound of the alkoxysilane oligomer.

The above alkoxysilane oligomer and a hexaalkyldisiloxane compound represented by the general formula (II) are mixed and used as a coating solution for forming a silica-based film.
In this case, the alkoxysilane oligomer is used as it is or in the form of the alkoxysilane oligomer liquid. When the alkoxysilane oligomer itself is used, it is dissolved in an appropriate solvent and used as a silica-based coating solution. Is used, a silica-based coating liquid is formed by mixing with a hexaalkyldisiloxane compound represented by the general formula (II), but a solvent may be further added. It is preferable to use an organic solvent as the solvent. Examples of the organic solvent include alcohols such as methanol, ethanol, propanol and butanol; acetates such as methyl acetate, ethyl acetate, propyl acetate and butyl acetate; glycol acetate solvents such as ethylene glycol monomethyl acetate and ethylene glycol diacetate; Various solvents such as amide solvents such as N, N-methyl-2-pyrrolidone and glycol ether solvents are used, and one or more of these solvents are used.

The solvent is contained in a coating solution for forming a silica-based film.
It is preferable to use the alkoxysilane oligomer and the hexaalkyldisiloxane compound in an amount such that the total amount is 15 to 50% by weight. When the prepared coating solution for forming a silica-based film is separated into two layers, the upper layer is almost always a solvent. Therefore, it is preferable that the lower layer is separated and used as a silica-based film-forming coating solution.

In order to form an oxide film using the coating solution thus obtained, the coating solution is formed by forming a silicon wafer, a metal plate such as aluminum, a silicon wafer having a metal formed on its surface, and a circuit. After coating on a substrate such as a silicon wafer by a dipping method, a spin coating method, or the like, drying is performed at 50 to 200 ° C., preferably 100 to 150 ° C., and then 300 to 500 ° C. in a nitrogen atmosphere. Preferably, firing is performed at 300 to 450 ° C. A semiconductor device can be obtained by using this silica-based coating as an interlayer film (insulating interlayer film) having a multilayer wiring structure.

The oxide film obtained by using the coating solution of the present invention has improved adhesion to metal as compared with an oxide film obtained by using a conventional hydrolysis condensate of alkoxysilane. In addition, an oxide film having the same thermal stability and film formability as an oxide film obtained by using a conventional hydrolysis condensate of alkoxysilane is formed.

[0018]

The present invention will be described below in more detail with reference to examples. Example 1 51.0 g of tetramethoxysilane, 45.0 g of dimethyldimethoxysilane, and 40.0 g of trimethyltrimethoxysilane were mixed, and 50.50 g of water was added to the mixture (liquid).
An aqueous solution in which 0.5 g of maleic acid was dissolved in 0 g was added dropwise over 1 hour under stirring. After stirring for 5 hours after dropping,
32 g of hexamethyldisiloxane was added, and the mixture was further stirred for 1 hour to obtain a coating solution for forming a silica-based film. When this coating solution was placed in a beaker and kept in a constant temperature bath at 23 ° C. for one week, the coating solution was separated into two layers. This coating solution is 23 ° C
Even when left in a constant temperature bath for 1 month, it was stable without separating into two layers and gelling. The upper layer of the coating liquid separated into the two layers was separated and removed from the lower layer liquid by decantation.

The remaining lower layer was coated on a silicon wafer at 2,000 rpm using a spinner as a coating solution, dried for 5 minutes on a hot plate controlled at 150 ° C., and subsequently controlled at 250 ° C. 5 on hot plate
After drying for 1 minute and sintering at 450 ° C. for 1 hour in an electric furnace under a nitrogen atmosphere, a colorless and transparent coating having no cracks and no irregularities on the surface was obtained. When the film thickness of this film was measured, it was 2.7 μm.

Example 2 75.0 g of tetramethoxysilane and 70.0 g of dimethyldimethoxysilane were mixed, and this mixture (liquid) was mixed.
An aqueous solution in which 0.6 g of maleic acid was dissolved in 55.0 g of water was added dropwise over 1 hour with stirring. After stirring for 5 hours after the completion of the dropwise addition, 49 g of hexaethyldisiloxane was added,
The mixture was further stirred for 1 hour to obtain a coating liquid for forming a silica-based film.
When this coating solution was placed in a beaker and kept in a constant temperature bath at 23 ° C. for one week, the coating solution was separated into two layers. This coating solution was stable without being gelled while being separated into two layers even when left in a thermostat at 23 ° C. for one month. The upper layer of the coating liquid separated into the two layers was separated and removed from the lower layer liquid by decantation.

The remaining lower layer was coated on a silicon wafer at 3000 rpm using a spinner as a coating solution, dried on a hot plate controlled at 150 ° C. for 5 minutes, and then controlled at 250 ° C. 5 on hot plate
After drying for 1 minute and sintering at 450 ° C. for 1 hour in an electric furnace under a nitrogen atmosphere, a colorless and transparent coating having no cracks and no irregularities on the surface was obtained. When the film thickness of this film was measured, it was 1.8 μm.

Comparative Example 1 51.0 g of tetramethoxysilane, 45.0 g of dimethyldimethoxysilane and 40.0 g of trimethyltrimethoxysilane were mixed, and 50.50 g of water was added to the mixture (liquid).
An aqueous solution in which 2.0 g of phosphoric acid was dissolved in 0 g was added dropwise over 1 hour with stirring, and after the completion of the addition, the mixture was stirred for 5 hours. Then, the coating solution was put into a beaker and left in a thermostat at 23 ° C. for 3 days. However, the coating solution gelled.

Comparative Example 2 75.0 g of tetramethoxysilane and 70.0 g of dimethyldimethoxysilane were mixed, and this mixture (liquid) was mixed.
An aqueous solution in which 0.5 g of maleic acid was dissolved in 55.0 g of water was added dropwise over 1 hour with stirring. After stirring for 5 hours after completion of the dropping, 80 g of hexamethyldisiloxane was added,
The mixture was further stirred for 1 hour to obtain a coating liquid for forming a silica-based film.
When this coating solution was placed in a beaker and kept in a constant temperature bath at 23 ° C. for one week, the coating solution was separated into two layers. The upper layer of the coating liquid separated into the two layers was separated and removed from the lower layer liquid by decantation.

The remaining lower layer was applied as a coating liquid on a silicon wafer at 3000 rpm using a spinner, dried on a hot plate controlled at 150 ° C. for 5 minutes, and then controlled at 250 ° C. 5 on hot plate
After drying for 1 minute and firing for 1 hour at 450 ° C. in an electric furnace in a nitrogen atmosphere, irregularities were generated on the surface of the coating.

[0025]

According to the first aspect of the present invention, the coating liquid for forming a silica-based film can form a film having excellent storage stability and excellent film-forming properties, and excellent crack resistance and surface smoothness. According to the method of the second aspect, a coating liquid for forming a silica-based film, which can form a film having excellent storage stability and thick film-forming properties, and excellent crack resistance and surface smoothness, can be obtained. The silica-based coating according to claim 3 can have a large thickness, and is excellent in crack resistance and surface smoothness.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takenori Narita 4-3-1-1, Higashicho, Hitachi City, Ibaraki Pref. Hitachi Chemical Co., Ltd. Semiconductor & Liquid Crystal Materials Division Development Center (72) Inventor Shigeru Nobe Ibaraki 3-1 Higashi-cho, Hitachi City, Hitachi Pref. Hitachi Chemical Co., Ltd.

Claims (3)

[Claims] (A) General formula (I) (Wherein R represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 0 to 2). A siloxane polymer obtained by hydrolyzing and polycondensing an alkoxysilane compound represented by the formula (B): Formula (II) (Wherein R ′ represents an alkyl group having 1 to 4 carbon atoms)
A coating liquid for forming a silica-based film, comprising a hexaalkyldisiloxane compound represented by the formula: (A) General formula (I) Wherein R represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 0 to 2. An aqueous solution of a siloxane polymer obtained by hydrolyzing and polycondensing an alkoxysilane compound represented by the formula (B): ) General formula (II) (Wherein R ′ represents an alkyl group having 1 to 4 carbon atoms)
A method for producing a coating solution for forming a silica-based film, characterized by mixing a hexaalkyldisiloxane compound represented by the formula: 3. A silica-based coating formed using the coating solution for forming a silica-based coating according to claim 1.