JPH0766188A - Semiconductor device - Google Patents

Abstract

PURPOSE:To provide a semiconductor device having a silica based insulation film excellent in insulation, mechanical strength, chemical resistance, etc., in which crack is prevented by setting low dielectric constant, low etching, and low shrinkage ratio at the time of film deposition. CONSTITUTION:The semiconductor device has a silica based insulation film formed of a coating liquid having ion concentration of 1.0 millimol/l or less and containing a reaction product of a silica sol (A) obtained through hydrolytic polycondensation of alkoxy silane shown by a general formula RnS(OR')4-n (R, R' represent 1-8C alkyl group, aryl group, or vinyl group, and n is an integer of 0-3) and an alkoxy silane or partial hydrolyzate thereof.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD OF THE INVENTION The present invention has a low relative permittivity and an etch rate, and a low shrinkage rate during film formation. Therefore, it is free from cracks and is excellent in insulation, mechanical strength, chemical resistance and the like. The present invention relates to a semiconductor device having a silica-based insulating film.

[0002]

BACKGROUND OF THE INVENTION Conventionally, silica-based insulating films have been formed for various purposes in semiconductor devices. In a conventional semiconductor device, for example, a silica-based insulating film is formed on a silicon substrate. In a semiconductor integrated circuit having a multilayer wiring structure, the silica-based insulating film is used to insulate the wiring layers from each other. A silica-based insulating film is used to protect the element surface or the PN junction part of a semiconductor device.

Such a silica-based insulating film is generally a CV.
It is formed by a vapor phase method such as D method or plasma CVD method.
Further, conventionally, such a silica-based insulating film has a coating film obtained by applying a coating solution containing an organosilicon compound such as silanol dissolved or dispersed in alcohol to a substrate by a spin coating method or the like to obtain a coating film of about 800. It is also practiced to form a silica-based insulating film by heating at a temperature of ℃ and curing.

However, the silica-based insulating film obtained by the conventional coating film forming method such as the spin coating method is caused by the decomposition of undecomposed organic residues of the organosilicon compound contained in the film. There is a problem that defects such as voids and pinholes are generated, and thus the denseness of the film is lost and the relative dielectric constant cannot be reduced.

Further, in the above-mentioned conventional method, there is a problem that the shrinkage rate of the film is large in the process of forming the film, so that the silica-based insulating film is apt to be cracked especially when the film is thick. .

Prior to the present invention, the present inventors have found that the general formula R
_n Si (OR ') _4-n (In the formula, R and R'have 1 to 8 carbon atoms.
Represents an alkyl group, an aryl group or a vinyl group of
Is an integer of 0 to 3. ) A silica-based coating liquid containing a silica sol (A) obtained by hydrolytic polycondensation of an alkoxysilane and a reaction product of the alkoxysilane or a partial hydrolyzate thereof (B). When the insulating film is formed, defects such as voids and pinholes do not occur, it is extremely dense, the relative dielectric constant and the etching rate are small, and the shrinkage rate during film formation is small.
It has been found that a silica-based insulating film excellent in adhesiveness, mechanical strength, chemical resistance, moisture resistance, insulating properties, etc. can be obtained without cracking during film formation (JP-A-4-10418).
issue).

By the way, in the semiconductor device having the silica-based insulating film as described above, it is said that the more defects the silica-based insulating film has, the more dense it is.

[0008] Therefore, the inventors of the present invention, more voids,
As a result of extensive studies to provide a semiconductor device having a dense silica-based coating with few pinholes, an alkali used as a catalyst in obtaining a silica sol by hydrolytic polycondensation of an alkoxysilane represented by the above formula, or When a semiconductor device having a silica-based insulating film is manufactured using a coating liquid in which an acid or alkali used as a catalyst when partially hydrolyzing an alkoxysilane remains as an ion, the silica-based insulating film causes It has been found that the film has voids, pinholes, etc., or the film properties such as insulation are deteriorated.

As a result of further studies, the present inventors have found that
When a silica-based insulating film is formed on a semiconductor device by using a coating solution having an extremely low ion concentration such as an ion concentration of 1.0 mmol / liter or less, a dense silica-based insulating film with few voids and pinholes is formed. The inventors have found that a semiconductor device having the same can be obtained, and completed the present invention.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems of the prior art, and is extremely dense with almost no voids, pinholes, etc., and has excellent adhesion, mechanical strength and resistance. It is an object of the present invention to provide a semiconductor device having a silica-based insulating film which is excellent in chemical resistance, moisture resistance, insulation, etc., has a low relative dielectric constant, and has a low etching rate.

[0011]

SUMMARY OF THE INVENTION A semiconductor device according to the present invention has the general formula R _n
Alkoxysilane represented by Si (OR ') _4-n (in the formula, R and R'represent an alkyl group, an aryl group or a vinyl group having 1 to 8 carbon atoms, and n is an integer of 0 to 3). A silica-based insulating film-forming coating solution containing a reaction product of the silica sol (A) obtained by hydrolytic polycondensation of the alkoxysilane or its partial hydrolyzate (B). It is characterized by having a silica-based insulating film formed from a coating liquid for forming an insulating film having an ion concentration of 1.0 mmol / liter or less.

[0012]

DETAILED DESCRIPTION OF THE INVENTION The semiconductor device according to the present invention will be specifically described below. The semiconductor device according to the present invention is
For example, when a PN junction is included in a semiconductor device on a silicon substrate, between wiring layers of a semiconductor integrated circuit having a multilayer wiring structure, a specific silica-based insulating film is provided on the PN junction or the element surface. Have

The specific silica type insulating film is formed from the following coating liquid. The silica-based insulating film formed on the semiconductor device according to the silica-based insulating film-forming coating liquid present invention, the general formula _{R n Si (OR ') 4} -n ( wherein, R, R' is 1 to the number of carbon atoms 8 represents an alkyl group, an aryl group or a vinyl group, n is an integer of 0 to 3), and a silica sol (A) obtained by hydrolytic polycondensation of an alkoxysilane represented by A reaction product with the hydrolyzate (B) is included.

The ion concentration in the coating liquid for forming a silica-based insulating film is 1.0 mmol / liter or less, preferably 0.6 mmol / liter or less. This ion concentration means the total ion concentration of cations and anions in the coating liquid, and in the present invention, the cation concentration and anion concentration are measured as follows, for example.

90 ml of 10 ml of coating liquid for forming a silica type insulating film
After mixing with ml of purified pure water and stirring for 1 hour at room temperature, this mixed solution is filtered, and 100 ml of purified pure water is passed through the filter medium after filtration to collect the filtrate.

The metal ion concentration contained in the recovered filtrate is measured by the atomic absorption method, and the ammonium ion concentration and the anion concentration are measured by the ion chromatography method. In the present invention, the ion concentration in the coating liquid for forming a silica-based insulating film is extremely low at 1.0 mmol / liter or less, so that there are almost no voids, pinholes, etc. as compared with the conventional coating, and it is dense. It is possible to form a silica-based insulating film having excellent adhesion, mechanical strength, chemical resistance, moisture resistance, insulation, etc. and a low relative dielectric constant on a semiconductor device.

That is, the silica-based insulating film forming coating solution containing the reaction product of the silica sol (A) with the alkoxysilane or its partial hydrolyzate (B) was used as a catalyst during the hydrolysis of the alkoxysilane. It contains acid or alkali and exists as ions in the coating liquid.

These acids or alkalis act as a polycondensation catalyst when the polycondensation of the alkoxysilane contained in the coating liquid proceeds further to form a film.
For this reason, the polycondensation rate of the alkoxysilane contained in the coating solution becomes faster during the film formation, and the film is formed with the acid or alkali in the coating solution or part of the organic solvent taken up. May progress. Of these, a part of the organic solvent is gasified and removed when the coating formed on the substrate is heated and cured, but the traces may become voids or pinholes, and therefore The denseness of the obtained silica-based insulating film is reduced.

Even after the coating is heated and cured, if some of the above-mentioned acids or alkalis or metal ions remain in the coating, they act as impurities and, for example, a silica-based insulating film. In some cases, the insulation properties of the

In the present invention, ions contained in the coating liquid such as acid ions or alkali ions remaining in the coating liquid as described above, and trace amounts of metal ions used as catalysts or remaining as impurities. By removing the cause of the occurrence of voids, pinholes, etc. during film formation, the insulating property of the silica-based insulating film obtained at the same time is improved, and a silica-based insulating film with a low relative dielectric constant is obtained. You can

Manufacturing Method of Coating Liquid for Forming Silica Insulating Film The coating liquid for forming a silica type insulating film as described above contains silica sol (A) used as a raw material and alkoxysilane or its partial hydrolysis during the manufacturing process. Either the liquid containing the substance (B) or the coating liquid obtained from these raw materials is treated with a cation exchange resin and an anion exchange resin to adjust the ion concentration in the coating liquid to 1. It can be produced by adjusting the amount to 0 mmol / liter or less.

When the treatment with the cation exchange resin and the treatment with the anion exchange resin are performed, the cation exchange resin and the anion exchange resin may be alternately treated, or the cation exchange resin and the cation exchange resin may be used. It may be treated with a mixed resin with an anion exchange resin.

The silica sol (A) used as a raw material for the coating liquid can be obtained by the following method.
That is, the silica sol (A) is obtained by subjecting an alkoxysilane represented by the following general formula to hydrolysis polycondensation in the presence of water, an organic solvent and an alkali catalyst.

R _n Si (OR ') _{4-n In the} formula, n represents an integer of 0 to 3, and R and R'have 1 carbon atoms.
Represents an alkyl group, an aryl group, or a vinyl group.

Specific examples of such alkoxysilanes include tetramethoxysilane, tetraethoxysilane,
Tetraisopropoxysilane, tetrabutoxysilane,
Tetraoctylsilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane,
Examples thereof include methyltriisopropoxysilane, methyltributoxysilane, octyltriethoxysilane, phenyltrimethoxysilane, vinyltrimethoxysilane, dimethyldimethoxysilane, diethyldiethoxysilane, trimethylmonomethoxysilane, and triethylmonoethoxysilane.

In the present invention, these alkoxysilanes may be used alone or in combination of two or more kinds. Examples of the organic solvent include alcohols, ketones, ethers, esters and the like, and more specifically,
For example, alcohols such as methanol, ethanol, propanol and butanol, ethylene glycol ethers such as methyl cellosolve and ethyl cellosolve, glycols such as ethylene glycol and propylene glycol, and ethers such as methyl acetate, ethyl acetate and methyl lactate are used. To be

As the alkali catalyst, compounds showing alkalinity in an aqueous solution such as ammonia, amine, alkali metal catalyst, quaternary ammonium compound and amine coupling agent are used, and the pH of the reaction mixture is preferably 7 to 12. Is used in an amount such that it is 8-11.

The method for preparing the silica sol (A) will be described in more detail. For example, while stirring a water-alcohol mixed solvent, an alkoxysilane and an alkali catalyst such as aqueous ammonia are added to the mixed solvent. React with alkoxysilane.

At this time, water is 5 to 50 moles, preferably 5 to 1 mole of Si-OR groups contained in the alkoxysilane.
The amount of the alkali catalyst used is such that the above-mentioned pH is reached, for example, 0.01-1.0.
It is blended in an amount such that it is mol / SiO ₂ mol, preferably 0.05 to 0.8 mol / SiO ₂ mol.

The hydrolysis polycondensation reaction of the alkoxysilane is usually carried out at a temperature not higher than the boiling point of the solvent used under normal pressure, preferably at a temperature 5 to 10 ° C. lower than this boiling point. It can also be carried out under pressure in a pressure vessel, and in this case, it is carried out at a temperature higher than the boiling point of the solvent under normal pressure.

When the alkoxysilane is hydrolyzed under such conditions, polycondensation of the alkoxysilane proceeds three-dimensionally, silica particles are produced, and the produced silica particles grow.

In this way, silica particles are produced.
After the growth, the heat treatment may be performed at a temperature not higher than the boiling point of the solvent used for a certain period of time. By carrying out such heat treatment, polycondensation of alkoxysilane is further promoted, and a silica sol in which silica particles having a high density are dispersed can be obtained.

A silica sol is thus obtained,
The silica sol (A) component of the coating liquid for forming a silica-based insulating film used when manufacturing the semiconductor device according to the present invention has a uniform average particle size of about 50 to 500 angstroms, particularly 100 to 500 angstroms. A silica sol in which particles are dispersed in a solvent is preferable. When the particle size is less than 50 angstroms, when a silica-based insulating film is formed on a semiconductor device by using a coating liquid obtained by using silica sol containing such silica particles as a raw material, the formed silica-based insulating film has a film surface. When cracks may occur, and when the average particle size of silica particles contained in the silica sol exceeds 500 angstroms, many voids occur in the coating film, and a dense silica-based insulating film cannot be formed in the semiconductor device. There is.

In the silica sol, silica particles are S
Approximately 50 wt% or less, preferably 40 wt% in terms of iO _2.
It is desirable that the content is as follows. The content of silica particles contained in this silica sol is 50% by weight.
If it exceeds, gelation tends to occur easily.

As the silica sol (A), the unpurified silica sol obtained by the above method can be used as it is, but as will be described later, the silica sol (A) and the alkoxysilane or its partial hydrolyzate (B) are used. Before carrying out the reaction, by means such as ultrafiltration from silica sol in advance,
It is preferable to replace the solvent with water from a mixed solvent of water and an organic solvent in order to obtain a silica-based insulating film forming coating solution used in manufacturing the semiconductor device according to the present invention as described above. .

Such solvent replacement operation may be carried out before the above-mentioned heat treatment of the silica sol. The ion concentration in the coating liquid for forming a silica-based insulating film used when manufacturing the semiconductor device according to the present invention depends on the cation exchange resin and the anion exchange resin with respect to the silica sol obtained as described above. It can also be adjusted by performing deionization treatment.

The silica sol (A) thus obtained and the alkoxysilane or its partial hydrolyzate (B) are used in the coating liquid for forming a silica-based insulating film used when manufacturing the semiconductor device according to the present invention. ) And the reaction product obtained by reacting with.

Used in the reaction with the above silica sol (A)
Alkoxysilane as a raw material for silica sol (A)
Similar to the used alkoxysilane, the general formula R_nSi (O
R ') _4-n(In the formula, R and R'are alkyl having 1 to 8 carbons.
Represents a group, an aryl group or a vinyl group, and n is 0 to 3
It is an integer. ) Alkoxysilane
Selected as a raw material for silica sol (A)
It does not have to be the same as the alkoxysilane used.

During the reaction process between the silica sol (A) and the alkoxysilane or its partial hydrolyzate (B), the growth of silica particles or the formation of new silica particles does not occur in the silica sol, and the silica sol (A) is contained in the silica sol (A). On the surface of the present silica particles, a binding reaction between the silica particles and a new alkoxysilane or its partial hydrolyzate (B) occurs, and as a result, a semiconductor having a silica-based insulating film that meets the object of the present invention. A coating liquid suitable for use in manufacturing a device can be obtained.

A reaction product of silica sol (A) and an alkoxysilane can be used as an insulating film forming component of such a coating liquid for forming a silica-based insulating film. It is preferable to use a reaction product with a decomposition product. When the silica sol (A) and the partial hydrolyzate of the alkoxysilane are mixed and reacted as described above, gelation due to aggregation of the sol tends not to occur.

When the partial hydrolysis of the alkoxysilane is carried out, water, an organic solvent, an acid or an alkali catalyst is usually used. Examples of the organic solvent and the alkali catalyst include those mentioned above. As the acid catalyst, specifically, an inorganic acid such as hydrochloric acid, nitric acid, sulfuric acid, an organic acid such as acetic acid or oxalic acid, or a compound showing acidity in an aqueous solution such as metal soap is used.

The amount of water used for partial hydrolysis of the alkoxysilane is usually the amount of Si contained in the alkoxysilane.
0.1 to 2 mol, preferably 0.5 per mol of the OR group.
~ 2 moles. When an acid catalyst is used in the partial hydrolysis of alkoxysilane, the pH of the reaction solution is usually 0 to 6, preferably 1 to 3, and when an alkali catalyst is used. The reaction solution is used in such an amount that the pH is usually 7 to 10, preferably 7 to 8.

The molecular weight of the partially hydrolyzed alkoxysilane obtained under the above conditions is about 100 to 10,000, preferably 500 to 5, in terms of polystyrene equivalent molecular weight.
It is desirable that it is 000.

The partial hydrolyzate of alkoxysilane can be obtained by the above method, but can also be obtained by the following method. 1) General formula R ¹ _n Si (OR ² ) _4-n (In the formula, R ¹ represents an alkyl group having 1 to 8 carbon atoms, an aryl group or a vinyl group, and R ² represents an alkyl group having 1 to 4 carbon atoms. , An aryl group or a vinyl group, and n is an integer of 0 to 3.)
One or more of the alkoxysilanes represented by
A method in which partial hydrolysis is carried out in the presence of an organic solvent, water and an alkali catalyst, and then the resulting partially hydrolyzed product is further partially hydrolyzed in the presence of water and an acid catalyst (Japanese Patent Laid-Open Publication No. HEI 3-30083).
54279).

2) General formula R ¹ _n Si (OR ² ) _4-n (In the formula, R ¹ represents an alkyl group having 1 to 8 carbon atoms, an aryl group or a vinyl group, and R ² has 1 to 4 carbon atoms. Represents an alkyl group, an aryl group or a vinyl group, and n is an integer of 0 to 3) and partially hydrolyzes one or more alkoxysilanes represented by the formula (1) in the presence of an organic solvent, water and an acid catalyst. A method of decomposing, and then bringing the obtained partial hydrolyzate into contact with an alkali, and acidifying the liquid thus obtained by adding an acid if necessary (JP-A-3-115379).

Examples of the organic solvent, acid catalyst and alkali catalyst used in the above method include those mentioned above. The ion concentration in the coating liquid for forming a silica-based insulating film used when manufacturing the semiconductor device according to the present invention is positive relative to the liquid containing the partial hydrolyzate of alkoxysilane obtained as described above. It can also be adjusted by performing deionization treatment with an ion exchange resin and an anion exchange resin.

The silica sol (A) as described above and the alkoxysilane or its partial hydrolyzate (B) are contained in the coating liquid for forming a silica-based insulating film used when manufacturing the semiconductor device according to the present invention. Is the weight of the silica particles contained in the silica sol (A) in terms of SiO ₂ (W _A ) / alkoxysilane or its partial hydrolyzate (B).
₂ in terms of the weight (W _B) is 0.1 to 10.0, preferably preferably contains mixed in such a weight ratio becomes 0.25 to 4.0.

When the weight ratio (W _A / W _B ) exceeds 10.0, a coating solution containing a reaction product of such a silica sol (A) and an alkoxysilane or its partial hydrolyzate (B) is formed. The resulting coating has excellent heat resistance and moisture resistance, but cracks tend to occur as the film thickness increases. On the other hand, when the weight ratio (W _A / W _B ) is less than 0.1, The heat resistance and moisture resistance tend to be poor.

After the silica sol (A) as described above and the alkoxysilane or its partial hydrolyzate (B) are mixed, at a temperature of about 100 ° C. or lower, preferably 80 ° C. or lower, usually 0.5 to The heat treatment is carried out for 5 hours, preferably 1 to 3 hours, whereby a silica-based insulating film forming coating solution used in manufacturing the semiconductor device according to the present invention is obtained. The lower limit temperature of this heat treatment is not particularly limited, but the lower the temperature, the longer the reaction time and the lower the productivity. On the other hand, if the temperature exceeds 100 ° C, the hydrolysis reaction of the alkoxysilane proceeds too much, which is not preferable.

Next, the silica-based insulating film-forming coating liquid thus obtained is subjected to deionization treatment with a cation exchange resin and an anion exchange resin, so that the ion concentration in the coating liquid is below a specified value. . As described above, the liquid containing the silica sol (A) and the partial hydrolyzate of alkoxysilane (B) has been previously subjected to deionization treatment with a cation exchange resin and an anion exchange resin. If the ion concentration of the obtained coating liquid is not more than the specified value, it is not necessary to perform the above-mentioned deionization treatment on the coating liquid newly obtained.

Manufacture of Semiconductor Device The semiconductor device according to the present invention is 1) First, the silica-based insulating film forming coating solution obtained as described above is applied to a semiconductor integrated circuit having a multilayer wiring structure on a silicon substrate. A spray method, a spin coating method, a dip coating method, a roll coating method, a screen printing method, a transfer printing method, on a predetermined surface of the semiconductor device such as a wiring layer, a surface of an element mounted on the semiconductor device or a surface of a PN junction portion. Steps (1) and 2) of applying by a method such as the above, and then, the coating film thus formed on the predetermined surface of the semiconductor device at 300 to 900 ° C.
It is preferably produced by including a step (2) of heating to a temperature of 450 to 800 ° C.

By the above steps (1) and (2), a semiconductor device having a silica-based insulating film formed on a predetermined surface is obtained. Semiconductor Device A semiconductor device according to the present invention is provided on a predetermined surface of a semiconductor device, such as a silicon substrate, wiring layers of a semiconductor integrated circuit having a multilayer wiring structure, a surface of an element mounted on the semiconductor device or a surface of a PN junction portion. , And has the silica-based insulating film formed as described above.

The thickness of the silica-based insulating film thus formed on the semiconductor device varies depending on the position in the semiconductor device where the silica-based insulating film is formed. For example, the silica-based insulating film is formed on a silicon substrate. When formed, it is usually about 1000 to 2500 angstroms, and when the silica-based insulating film is formed between wiring layers of a semiconductor integrated circuit having a multilayer wiring structure, it is about 500.
It may be necessary to be 0 angstroms or more.

[0054]

According to the present invention, there are almost no voids, pinholes, etc., and it is extremely dense, has a low relative permittivity and an etch rate, has a low shrinkage rate during film formation, and has a crack during film formation. It is possible to obtain a semiconductor device having a silica-based insulating film which is free from cracking and is excellent in adhesion, mechanical strength, chemical resistance, moisture resistance, insulation and the like.

Further, as a remarkable effect of the present invention, it is possible to make the wiring multi-layered and the contact holes can be freely brought close to each other without fear of generation of unnecessary parasitic capacitance, and to realize a miniaturized and highly reliable semiconductor device. It is now possible to provide.

That is, the organic SOG film, which has been conventionally used as an interlayer insulating film for the purpose of ensuring flatness, generally has a very high relative permittivity of about 6, and the proximity of wirings by bringing multi-layered wirings and contact holes close to each other. As a result, an unnecessary capacitor tends to be parasitic between the wiring layers. On the other hand, in the semiconductor device according to the present invention, the relative dielectric constant of the interlayer insulating film is relatively low at about 4.5, and the wiring layers The parasitic capacitance is small even when they are close to each other. Therefore, the miniaturized and highly reliable semiconductor device as described above has become possible.

[0057]

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

[0058]

Example 1-Preparation of silica sol-To a mixed solution of 101.5 g of pure water and 406.1 g of methanol was added 110.4 g of ethyl silicate-28 (SiO ₂ concentration; 28% by weight, manufactured by Tama Chemical Industry Co., Ltd.). After the addition, 89.5 g of 5% aqueous ammonia was added over 3 hours while the liquid was heated to maintain the temperature of the liquid at 65 ° C., whereby silica particles were generated in the liquid. The liquid after the addition was maintained at the same temperature for 1 hour to age the silica particles in the liquid. Then, from the liquid containing the silica particles, unreacted ethyl silicate, methanol and ammonia contained in the liquid are removed by ultrafiltration, and pure water is added at the same time, and the SiO ₂ concentration is 5% by weight.
A silica sol A in which silica particles having an average particle diameter of 100 Å were dispersed was obtained.

-Preparation of Partial Hydrolyzed Alkoxysilane- Concentrated nitric acid was added to a mixed solution of 357.1 g of ethyl silicate-28, 402.9 g of ethanol and 240.0 g of pure water to adjust the pH of the mixed solution to 1 Adjusted to .5.
By heating this mixed solution at 50 ° C. for 1 hour, an alkoxysilane partial hydrolyzate a was obtained.

-Preparation of coating liquid-Silica sol A obtained as described above and alkoxysilane partial hydrolyzate a were mixed in a solid content weight ratio of 7/3 and then at 50 ° C for 1 hour. By heating, the silica sol and the alkoxysilane partial hydrolyzate were reacted. . Then, a liquid containing this reaction product is mixed with an equal amount of a cation exchange resin and an anion exchange resin (AG501,
Deionization was performed by passing through a column packed with Bio-Rad).

Next, the water and alcohol contained in this solution were distilled off by a rotary evaporator and then replaced with propylene glycol monopropyl ether to obtain Si.
A coating liquid I having an O ₂ concentration of 20% by weight was obtained.

-Evaluation of Coating Liquid for Forming Silica-based Insulating Film and Semiconductor Device-The ion concentration of the coating liquid thus obtained was measured, and this coating liquid was applied onto a silicon wafer by a spinner method to obtain 150 After drying at 5 ° C. for 5 minutes, baking was performed at 450 ° C. for 30 minutes in a nitrogen atmosphere to form a silica-based insulating film having a film thickness of 5000 Å, and the following evaluation was performed.

(1) Presence or absence of cracks: Presence or absence of cracks was judged by visual observation. (2) Etch rate: The film thickness before and after the silicon wafer with a silica-based insulating film was immersed for 5 minutes in an HF aqueous solution prepared by dissolving 5 ml of HF in 1 liter of pure water was measured, and the difference in film thickness before and after this was immersed. The value divided by the time was taken as the etch rate.

(3) Relative permittivity; An aluminum film was formed on the silica-based insulating film of the silicon wafer with the silica-based insulating film by a vapor deposition method, and the relative dielectric constant was measured with an impedance analyzer using this aluminum film as a measurement electrode. .

Table 1 shows the ion concentration of the coating liquid I and the evaluation results of the silica insulating film.

[0066]

EXAMPLE 2 - Preparation of silica sol - pure water 203.0g methyl silicate in a mixed solution of methanol 812.2g -51 (SiO ₂ concentration: 51 wt%, Tama Chemical Industry Co., Ltd.) 121.6g After the addition, while heating the liquid to maintain the liquid temperature at 45 ° C., 150 g of 5% ammonia water was added over 5 hours,
This produced silica particles in the liquid. The liquid after the addition was maintained at the same temperature for 1 hour to age the silica particles in the liquid. Then, unreacted ethyl silicate, methanol and ammonia contained in the liquid are removed from the liquid containing the silica particles by ultrafiltration, and pure water is added at the same time, and the SiO ₂ concentration is 5% by weight. A silica sol B having silica particles of 110 angstrom dispersed therein was obtained.

-Preparation of partial hydrolysis product of alkoxysilane- 196.1 g of methyl silicate-51, ethanol 6
1% ammonia water was added to a mixed solution of 83.9 g and pure water 120.0 g to adjust the pH of the mixed solution to 8.0. This mixed solution was heated at 50 ° C. for 1 hour to hydrolyze methyl silicate, and then the pH was adjusted to 2. with concentrated nitric acid.
It was adjusted to 5 and further heated at 50 ° C. for 30 minutes to obtain an alkoxysilane partial hydrolyzate b.

-Preparation of coating liquid-Same as in Example 1 except that the silica sol B thus obtained and the alkoxysilane partial hydrolyzate b were mixed in a solid content weight ratio of 1/1. Then, the reaction between the silica sol and the partial hydrolyzate of alkoxysilane, the deionization treatment of the solution containing the obtained reaction product and the solvent substitution were sequentially carried out to obtain a coating solution II having a SiO ₂ concentration of 20% by weight.

-Evaluation of Coating Liquid for Forming Silica-based Insulating Film and Semiconductor Device- The coating solution II obtained as described above was measured for ion concentration in the same manner as in Example 1, and further in the same manner as in Example 1. A semiconductor device evaluation sample was prepared, and the semiconductor device was evaluated using the obtained sample.

The results are shown in Table 1.

[0071]

[Example 3] -Preparation of silica sol-Silica sol A obtained in Example 1 was subjected to deionization treatment in the same manner as in the coating liquid of Example 1 to obtain silica sol C.

-Preparation of Partial Hydrolyzate of Alkoxysilane- Partial Hydrolyzate of Alkoxysilane Obtained in Example 2
The solution containing the same was subjected to deionization treatment in the same manner as in the coating solution of Example 1 to obtain an alkoxysilane partial hydrolyzate c.

—Preparation of Coating Solution— The silica sol C obtained as described above and the alkoxysilane partial hydrolyzate c were mixed in a solid content weight ratio of 3/7, and the same conditions as in Example 1 were applied. It was made to react with. Next, the liquid containing this reaction product was subjected to the same deionization treatment as in Example 1, and then water and alcohol contained in this liquid were distilled off with a rotary evaporator, followed by substituting with ethyl lactate to obtain SiO 2. ₂ Coating solution with a concentration of 20% by weight
I got III.

-Evaluation of Silica-based Insulating Film Forming Coating Liquid and Semiconductor Device- The coating liquid III obtained as described above was measured for ion concentration in the same manner as in Example 1, and further in the same manner as in Example 1. A semiconductor device evaluation sample was prepared, and the semiconductor device was evaluated using the obtained sample.

The results are shown in Table 1.

[0076]

[Example 4] -Preparation of silica sol-While maintaining a mixed solution of 139.1 g of pure water and 169.9 g of methanol at 60 [deg.] C., the mixed solution was mixed with a water / methanol mixed solution of ethyl silicate-28 (ethyl Silicate; 532.5 g, water / methanol mixed solvent; 2450 g, water / methanol weight ratio: 1/4) 2
982.5 g and 596.4 g of 0.25% aqueous ammonia were simultaneously added over 52 hours, thereby forming silica particles in the mixed solution. The liquid after the addition was maintained at the same temperature for 3 hours to age the silica particles in the liquid. Then, unreacted ethyl silicate, methanol and ammonia contained in the liquid are removed by ultrafiltration from the liquid containing the silica particles, and at the same time, pure water is added,
A silica sol D having a SiO ₂ concentration of 10% by weight and having silica particles having an average particle diameter of 250 Å dispersed therein was obtained.

-Preparation of partially hydrolyzed alkoxysilane-454.5 g of methyltrimethoxysilane, ethanol 1
Concentrated nitric acid was added to a mixed solution of 85.5 g and pure water 360.0 g to adjust the pH of the mixed solution to 1.0. By heating this mixed solution at 50 ° C. for 2 hours, partial hydrolysis of the alkoxysilane is carried out, and then 1% of this solution is added.
Aqueous ammonia was added to adjust the pH to 7.0, and this solution was heated at 50 ° C. for 2 hours to obtain an alkoxysilane partial hydrolyzate d.

-Preparation of coating liquid- Silica sol D obtained as described above and alkoxysilane partial hydrolyzate d were mixed at a solid content weight ratio of 7/3, and the same procedure as in Example 3 was carried out. Reaction of silica sol with partial hydrolysis product of alkoxysilane, deionization treatment of the liquid containing the obtained reaction product and solvent replacement are sequentially carried out, and Si
A coating liquid IV having an O ₂ concentration of 20% by weight was obtained.

-Evaluation of Coating Liquid for Forming Silica Insulating Film and Semiconductor Device- The ion concentration of the coating liquid IV obtained as described above was measured in the same manner as in Example 1, and further in the same manner as in Example 1. A semiconductor device evaluation sample was prepared, and the semiconductor device was evaluated using the obtained sample.

The results are shown in Table 1.

[0081]

[Example 5] -Preparation of silica sol-In place of ethyl silicate-28, 169.4 g of methyltrimethoxysilane and 266.3 g of ethyl silicate-28 were used.
A silica sol was prepared in the same manner as in Example 4 except that the above was used, the SiO ₂ concentration was 10% by weight, and the average particle size was 25.
A silica sol E having 0 angstrom silica particles dispersed therein was obtained.

-Preparation of Partial Hydrolyzate of Alkoxysilane- 227.3 g of methyltrimethoxysilane, 357.1 g of ethyl silicate-28, 175.0 g of ethanol and 240.0 g of pure water were added to a mixed solution of 1% ammonia water. The pH of the mixed solution was adjusted to 8.5. This mixed solution is heated at 50 ° C. for 2 hours to partially hydrolyze the alkoxysilane, and then a 95% aqueous acetic acid solution is added to adjust the pH to 4 and then the solution is adjusted to 5
By heating at 0 ° C. for 5 hours, an alkoxysilane partial hydrolyzate e was obtained.

-Preparation of coating liquid-Same as in Example 3 except that the silica sol E thus obtained and the alkoxysilane partial hydrolyzate e were mixed at a solid content weight ratio of 4/1. The silica sol was partially reacted with the alkoxysilane partial hydrolyzate, the liquid containing the obtained reaction product was subjected to deionization treatment and solvent substitution in order to obtain a coating liquid V having a SiO ₂ concentration of 20% by weight.

-Evaluation of Coating Solution for Forming Silica Insulating Film and Semiconductor Device- The ion concentration of the coating solution V obtained as described above was measured in the same manner as in Example 1, and further in the same manner as in Example 1. A semiconductor device evaluation sample was prepared, and the semiconductor device was evaluated using the obtained sample.

The results are shown in Table 1.

[0086]

[Comparative Examples 1 to 4] Coating liquids i to iv were prepared in the same manner as in Examples 1, 2, 4, and 5, respectively, except that the coating liquid was not deionized. The measurement was performed in the same manner as in Example 1, and a semiconductor device evaluation sample was prepared in the same manner as in Example 1, and the obtained sample was used to evaluate the semiconductor device.

The results are shown in Table 1.

[0088]

[Table 1]

[0089]

Example 6 Example 1 was formed on a semiconductor substrate provided with aluminum wiring having a line and space pitch of 1 μm.
The coating solution I obtained in 1 above was applied by spin coating, the obtained coated semiconductor substrate was dried at 150 ° C. for 5 minutes, and then heated at 400 ° C. for 30 minutes in a nitrogen atmosphere to form the aluminum wiring. A silica-based insulating film was formed on.
The thickness of the obtained silica-based insulating film was 5000 Å.

Further, a thickness of 300 is formed on the silica-based insulating film.
A 0 Å SiO ₂ film was provided by a CVD method to form an interlayer insulating film. RIE is applied to this interlayer insulating film.
After providing a 0.6 μm square contact hole by a dry etching method, a second-layer aluminum wiring was formed by a vapor deposition method to form a two-layer aluminum wiring element.

With respect to the interlayer insulating film of the two-layer aluminum wiring element thus obtained, the flatness and the presence or absence of cracks were measured. The flatness F of the interlayer insulating film was calculated by the following equation.

F = 1- (b / a) (where a and b represent the values shown in FIG. 1).
Indicates a cross section of the interlayer insulating film 1, reference numeral 2 indicates a semiconductor substrate, and the aluminum wiring layer 3 is formed on the semiconductor substrate 2.
Is formed and the interlayer insulating film 1 is formed on the semiconductor substrate 2 so as to cover the aluminum wiring layer 3.

In FIG. 1, symbol a indicates the height of the convex portion of the interlayer insulating film 1 measured with the surface of the semiconductor substrate 2 as a reference, and symbol b.
Indicates the uneven gap of the interlayer insulating film 2. The measurement results are shown in Table 2.

[0094]

[Examples 7 to 10 and Comparative Examples 5 to 8] Coating liquids II to V obtained in Examples 2 to 5 and coating liquids i to I obtained in Comparative Examples 1 to 4
A semiconductor device evaluation sample was prepared in the same manner as in Example 6 except that iv was used, and the obtained sample was used to evaluate the semiconductor device.

The results are shown in Table 2.

[0096]

[Table 2]

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an interlayer insulating film formed on a semiconductor substrate to cover an aluminum wiring layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Interlayer insulating film 2 Semiconductor substrate 3 Aluminum wiring layer a Height of convex portion b Concavity and convexity gap

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shindai ▲ Te ▼ 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Hideki Harada, Inventor 1015, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Within Fujitsu Limited

Claims (1)

[Claims] 1. The general formula R _n Si (OR ′) _4-n (wherein
R and R'represent an alkyl group having 1 to 8 carbon atoms, an aryl group or a vinyl group, and n is an integer of 0 to 3. ) A silica sol (A) obtained by hydrolytic polycondensation of an alkoxysilane represented by the formula (1), and the alkoxysilane or a partial hydrolyzate thereof (B).
A coating liquid for forming a silica-based insulating film, which comprises a reaction product with a silica-based insulating film, wherein the coating liquid for forming an insulating film has an ion concentration of 1.0 mmol / liter or less. A semiconductor device having.