JPH03116733A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To manufacture a semiconductor device having a silica insulating film including excellent insulation, excellent mechanical strength, chemical resistance, moisture resistance, etc., by coating a semiconductor substrate with silica film forming coating solution containing condensate of alkoxysilane partial hydrolyzate, and heating it. CONSTITUTION:Alkoxysilane represented by a general formula R1nSi(OR<2>)4-n (where R<1> is a hydrocarbon group, R<2> is 1-4C alkyl group, and n is 0-3) is partially hydrolyzed in the presence of organic solvent, water and acid, then obtained partial hydrolyzate is brought into contact with alkali to be prepared. A board 11 is coated with this silica film forming coating solution before the layer 13 is formed or the board 11 formed with the layer 13 is coated with the solution, then heated to provide a silica insulating film 15 on the substrate 11.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device provided with a silica-based insulating film having a specific dielectric constant.

TECHNICAL BACKGROUND OF THE INVENTION In order to increase the degree of integration of semiconductor integrated circuits, multilayer interconnections as shown in FIG. 1, for example, are used. To explain the manufacturing process of such multilayer wiring, a thermal oxide film 12 as an insulating film is formed on a substrate 11 made of silicon or the like, and then a first wiring layer 13 made of an aluminum film or the like is formed. Next, CVD method or plasma CV is applied on this.
An interlayer insulating film 14 such as a silica film or a silicon nitride film is deposited by the D method or the like, and a silica insulating film 15 is formed on this interlayer insulating film 14 to planarize this insulating film 14. A second layer is further formed on the insulating film 15 as necessary.
After depositing the interlayer insulating film 16, a second wiring layer (not shown) is formed.

The silica-based insulating film 15 described above has conventionally been applied by a so-called SOG method (Spin on Gl! II method) using a spin coating method or the like using a coating solution prepared by dissolving or dispersing an organosilicon compound such as silanol in alcohol. It was formed by heating and curing the obtained coating film (SOC film).

By the way, the silica-based insulating film provided on the substrate on which the wiring layer is formed as described above may have pinholes or voids, and may have poor insulation, mechanical strength, chemical resistance, moisture resistance, etc. In this respect, I was not completely satisfied.

In addition, the silica-based insulating film 15 formed as described above is
The problem is that the film is porous and has poor density, and that the etching solution permeates into the film when the through-hole is opened, etching unnecessary parts.

Furthermore, in a semiconductor device having multilayer wiring as described above,
In particular, during sputtering when opening through holes and forming the second wiring layer, wiring such as aluminum in the wiring layer may be oxidized and become aluminum oxide, increasing the resistance value and causing poor conductivity. there were.

Such poor conductivity in the wiring layer is caused by the fact that the silica-based insulating film contains re-adsorbed moisture, and this moisture oxidizes the sputtered aluminum particles, causing the insulating AI to oxidize.
It is presumed that this is caused by the generation of 203.

Furthermore, the silica-based insulating film formed by the above-mentioned coating method has a higher dielectric constant than the silica-based insulating film formed by the CVD method, and there is also a problem that the dielectric constant is larger.

In other words, in semiconductor devices of 1M or more, when the diameter of the through hole is 1 μm and the insulating film in the vicinity has a high dielectric constant, the impedance of the AI electrode increases due to electrostatic induction, resulting in a delay in response speed and an increase in power consumption. It has the disadvantage of inviting

Purpose of the Invention The present invention has been made in view of the above-mentioned prior art. It is an object of the present invention to provide a method for manufacturing a semiconductor device provided with a silica insulating film that has excellent properties such as mechanical strength, chemical resistance, and moisture resistance.

Summary of the Invention The method for manufacturing a semiconductor device according to the present invention is represented by the formula (wherein R1 is a hydrocarbon group, R2 is an alkyl group having 1 to 4 carbon atoms, and n is 0 to 3). An alkoxysilane is partially hydrolyzed in the presence of an organic solvent, water, and an acid, and the resulting partially hydrolyzed solution is then brought into contact with an alkali to produce a silica containing a condensate of a partially hydrolyzed alkoxysilane. A coating solution for forming a silica-based film or a coating solution for forming a silica-based film made by adding an acid to this coating solution to make it acidic is applied onto a semiconductor substrate and then heated to provide a silica-based insulating film on the semiconductor substrate. It is characterized by including a process.

DETAILED DESCRIPTION OF THE INVENTION A method for manufacturing a semiconductor device according to the present invention will be specifically described below.

In the semiconductor device obtained by the manufacturing method according to the present invention, for example, as shown in FIG. 1, a wiring layer 13 is provided on a substrate 11 such as silicon with a first insulating film 12 such as a thermal oxide film interposed therebetween. An interlayer insulating film 14 is provided on this wiring layer 13.

A silica-based insulating film 15 is provided on this interlayer insulating film 14 , and this silica-based insulating film 15 covers the glabella insulating film 14 .
This is a film for flattening the surface and forming a second wiring layer (not shown) thereon.

It is desirable that the silica-based insulating film formed on the semiconductor device obtained by the manufacturing method of the present invention has a dielectric constant of 3.0 to 4.5, preferably 3.0 to 4.0. If the dielectric constant of this silica-based insulating film exceeds 4.5, the above-mentioned problems will become noticeable and speed-up of semiconductor devices will be hindered, while if it is lower than 3.0, other properties of the film will be affected. There is a tendency for this to be harmed.

Furthermore, this silica-based insulating film was exposed to hydrogen fluoride in 1 liter of water.
The etching rate (input/min) calculated from the film thickness after 5 minutes of immersion in a cc-dissolved hydrogen fluoride aqueous solution and the film thickness before immersion is 25 people/min or less, preferably 20 people/min or less. It is desirable that there be.

Therefore, this silica-based insulating film is dense.

Note that the wiring layer 13 as described above is formed of a metal such as aluminum, for example. Also, interlayer insulating film 1
Specifically, 4 is a silicon nitride film, a silica film, etc., and these can be formed by a CVD method, a plasma CVD method, or the like.

In the semiconductor device obtained by the manufacturing method according to the present invention, the second wiring layer can also be formed directly on the silica-based insulating film 15, as shown in FIG.

Furthermore, in the semiconductor device obtained by the manufacturing method according to the present invention, as shown in FIG. Alternatively, the silica-based insulating film 15 described above may be directly formed as an interlayer insulating film. In this case, the second interlayer insulating film 1
6 can also be omitted.

Furthermore, in the semiconductor device obtained by the manufacturing method according to the present invention,
The first insulating film 12 shown in FIG. 1 may be formed using the coating liquid of the present invention.

Next, a method for manufacturing a semiconductor device according to the present invention will be explained.

In the method for manufacturing a semiconductor device according to the present invention, a coating liquid for forming a silica-based film prepared as described below is used.
A silica-based insulating film is provided on a semiconductor substrate by heating before the wiring layer is formed or after being applied onto the substrate on which the wiring layer is formed.

This coating liquid for forming a silica-based film contains an alkoxysilane represented by (wherein R is a hydrocarbon group, R2 is an alkyl group having 1 to 4 carbon atoms, and n is 0 to 3). It is prepared by partial hydrolysis in the presence of an organic solvent, water and an acid, and then contacting the resulting partial hydrolysis solution with an alkali.

The alkoxysilane used in the present invention is represented by (wherein R is a hydrocarbon group, R2 is an alkyl group having 1 to 4 carbon atoms, and n is 0 to 3).

Specific examples of the hydrocarbon group for R1 include a methyl group, an ethyl group, and a vinyl group.

Specifically, such alkoxysilanes include tetramethoxysilane, tetraethoxysilane, monomethyltrimethoxysilane, monomethyltriethoxysilane, dimethyldimethoxysilane, dimethyljethoxysilane, monoethyltrimethoxysilane, and monoethyltriethoxysilane. Silane, diethyldimethoxysilane, diethyljethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, etc. are used.

These alkoxysilanes may be used alone or in combination.

Examples of organic solvents for dissolving the alkoxysilanes mentioned above include alcohols such as methanol, ethanol, propatool, and butanol, ethylene glycol ethers such as methyl cellosolve and ethyl cellosolve, ethylene glycol, and propylene. Glycols such as glycol, ester acids such as methyl acetate, ethyl acetate, and methyl lactate are used.

These organic solvents may be used alone or in combination.

Specifically, the acid used is a compound that exhibits acidity in an aqueous solution, such as inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid, and organic acids such as acetic acid and oxalic acid.

In the present invention, first, the alkoxysilane as described above is
Partially hydrolyzed in the presence of organic solvents, water and acids.

At this time, the alkoxysilane is SiO2 in the reaction mixture.
It is desirable to use the amount of 3 to 25% by weight, preferably 5 to 20% by weight.

Water is used in an amount of 0.1 to 2 mol, preferably 0.5 to 1 mol, per mol of 5t-OR group of the alkoxysilane. If the amount of water is less than 0.1 mole per mole of 5t-OR group of the alkoxysilane, the hydrolysis of the alkoxysilane will tend to be insufficient, while if it exceeds 2 moles, the hydrolysis of the alkoxysilane will be insufficient. If the rate becomes too high, it tends to become difficult to control the degree of condensation polymerization of the alkoxysilane.

It is desirable to use the acid in an amount such that the pH of the reaction mixture is 0-6, preferably 2-4. pH of reaction mixture
The lower the value, the faster the hydrolysis rate of the alkoxysilane becomes, making it possible to reduce the amount of water added and to lower the partial hydrolysis rate.

The partial hydrolysis reaction of alkoxysilane is 10 to 10
It is desirable to carry out the reaction at a temperature of 0°C, preferably 20 to 60°C, and the above reaction time is extremely fast at high temperatures and low pH, but it is usually carried out within 5 hours, preferably within 3 hours.

When the partial hydrolysis reaction of alkoxysilane is carried out in the presence of an acid as described above, the alkoxysilane is partially hydrolyzed and a condensation product of a partially hydrolyzed alkoxysilane is produced. The molecular weight (polystyrene equivalent molecular weight) of this condensation product is 100 to 5.000, preferably 500 to 2.
000 is desirable.

If the molecular weight of the condensation product of the alkoxysilane partial hydrolyzate produced at this time is less than 100, organic residues (for example, OR groups) will remain in the silica-based film finally obtained, forming a dense film. On the other hand, 5.00
When it exceeds 0, the silica-based coating finally obtained tends to become porous.

Next, as described above, the alkoxysilane is dissolved in an organic solvent,
The reaction mixture obtained by partial hydrolysis in the presence of water and acid is contacted with an alkali.

At this time, water may be added to the reaction mixture as necessary, or new alkoxysilane may be added.

When the reaction mixture obtained by partial hydrolysis as described above is brought into contact with an alkali, the remaining alkoxysilane is partially hydrolyzed, and if necessary, new alkoxysilane is partially hydrolyzed. It is thought that conversion of the OH groups and OR groups remaining in the polycondensation product obtained in step 1 to siloxane bonds and promotion of the polycondensation reaction proceed.

Examples of alkalis include ammonia, amines, alkali metal hydroxides, quaternary ammonium compounds, etc.
A compound exhibiting alkalinity in aqueous solution is used in an amount such that the pH of the reaction mixture is 6-11, preferably 6-9.

Contact with alkali is carried out at 10-100°C, preferably 20-100°C.
Preferably, it is carried out at a temperature of 60°C.

The above-mentioned contact time varies greatly depending on the contact temperature, but is usually about 0.5 to 5 hours, preferably about 1 to 3 hours.

In this way, by partially hydrolyzing alkoxysilane in the presence of an acid and then contacting it with an alkali, a coating solution for forming a silica-based film containing a condensation product of a partially hydrolyzed alkoxysilane is obtained. The coating solution is usually alkaline. Then, by adding acid again to this coating liquid to make it acidic, preferably to a pH of 6 or less, the pot life of the coating liquid is improved and it becomes possible to store it for a longer period of time.

The coating liquid for forming a silica-based film obtained as described above is applied onto a semiconductor substrate, and then dried and baked to form a film on the substrate. The molecular weight of the condensation product of the alkoxysilane partial hydrolyzate is usually 100 to 10,000.
0, preferably 500 to 5,000. In order to apply the coating liquid onto the substrate, a conventional method such as a spray method, a spin code method, a dip coating method, a roll coating method, a screen printing method, a transfer printing method, etc. can be employed.

The above firing temperature is usually 300 to 900°C, preferably 4°C.
The temperature is about 50 to 800°C.

It is desirable that the silica-based film formed using the above-described coating liquid for forming a silica-based film has a dielectric constant of 3.0 to 4.5, preferably 3.0 to 4.0. Further, the etching rate of this silica-based coating is desirably 25 people/min or less, preferably 20 people/min or less. This silica-based coating is free from defects such as pinholes and cracks, is dense, and has excellent mechanical strength as well as chemical resistance, moisture resistance, and insulation properties. The reason why the above-mentioned dense silica-based coating can be obtained in the present invention is because a coating film with a low content of organic residues can be obtained by partially hydrolyzing alkoxysilane in the presence of an acid and then contacting it with an alkali. It is thought that this is because the generation of voids caused by decomposition of these residues is suppressed when the coating film is fired.

For example, in the case of an insulating film 12 formed on a semiconductor substrate, the thickness of the silica-based film formed in the present invention is usually 1,000 mm.
In the case of an interlayer insulating film, a silica-based film having a thickness of 5000 Å or more may be required. In such cases, as the alkoxysilane, use a single trialkoxysilane such as monomethyltrimethoxysilane, or a mixture of tetraalkoxysilane and trialkoxysilane such as monomethyltrimethoxysilane, or dialkoxysilane such as dimethyldimethoxysilane. It is preferable. In addition, in order to obtain a silica-based film with a film thickness of less than 5000, tetramethoxysilane, tetramethoxysilane,
Preferably, a tetraalkoxysilane such as tetraethoxysilane is used.

Tetraalkoxysilane and trialkoxysilane or dialkoxysilane may be used as a mixture from the beginning. For example, a partial hydrolysis step with an acid is performed using only tetraalkoxysilane, and upon contact with an alkali, trialkoxysilane is used. Alkoxysilane or dialkoxysilane may be added.

The mixing ratio of tetraalkoxysilane and trialkoxysilane or dialkoxysilane is 0.5 to 4.5:5 to 9:0 to 2 (weight ratio of tetraalkoxysilane nitrialkoxysilane: dialkoxysilane as 5102). ) is desirable.

When the amount of tetraalkoxysilane increases, the resulting silica-based film has excellent heat resistance and moisture resistance, but when a silica-based film is formed with a thick film thickness, cracks tend to occur easily. If the amount of silane or dialkoxysilane is large, the resulting silica-based coating tends to have poor heat resistance and moisture resistance.

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

Example 1 Tetraethoxysilane (Tama Chemical Industry Co., Ltd. Ethylsilicate-28,5+ 02 equivalent tetraethoxysilane concentration 2
8% by weight) 357g, 120g of water, and IPA 52
3g and stir, then add concentrated nitric acid to adjust the pH to 1.
Adjusted to. The resulting mixture was kept at 50°C for 1 hour,
Partial hydrolysis of tetraethoxysilane was carried out. The condensation product of the alkoxysilane partial hydrolyzate obtained after partial hydrolysis has a molecular weight of 1,500 in terms of polystyrene.
Met.

Next, 1% ammonia water was added to this reaction mixture to
After adjusting the temperature to H6, the temperature was maintained at 30° C. for 12 hours to prepare a coating solution for forming a silica-based film.

Example 2 250 g of tetraethoxysilane (manufactured by Tama Chemical Industry Co., Ltd., ethyl silica 1'-40,3+ 02 equivalent tetrafunctional toxysilane concentration 40% by weight), 60 g of water, and 690 g of ethyl cellosolve were mixed and stirred, and concentrated hydrochloric acid was added. pH
Adjusted to 2. The resulting mixed solution was kept at 50° C. for 2 hours to partially hydrolyze tetraethoxysilane. The condensation product of the alkoxysilane partial hydrolyzate obtained after the partial hydrolysis had a molecular weight of 1.000.

Next, 1% monoethanolamine was added to this reaction mixture [I] to adjust the pH to 7, and then the mixture was kept at 50° C. for 2 hours.

Concentrated hydrochloric acid was added again to the solution obtained in this way to adjust the pH.
4, and a coating liquid for forming a silica-based film was prepared.

Example 3 98 g of tetramethoxysilane (methyl silicate-51 manufactured by Tama Chemical Industries, tetramethoxysilane concentration 51% by weight in terms of S i 02), 90 g of water, and 812 g of propylene glycol monopropyl ether were mixed and stirred,
Tin octylate (TN-12 manufactured by Sakai Chemical Industries) was added to adjust the pH to 3. The resulting mixed solution was kept at 50° C. for 30 minutes to partially hydrolyze tetramethoxysilane. The condensation product of the alkoxysilane partial hydrolyzate obtained after the partial hydrolysis had a molecular weight of 800.

Next, 1% triethanolamine was added to this reaction mixture to adjust the pH to 7, and the mixture was kept at 30° C. for 1 hour to prepare a coating solution for forming a silica-based film.

Example 4 Methyl silicate-51118g used in Example 3,
72 g of water and 556 g of ethyl cellosolve were mixed and stirred, and the pH was adjusted to 1 by adding concentrated nitric acid. The resulting mixture was kept at 50° C. for 1 hour to partially hydrolyze tetramethoxysilane.

The condensation product of the alkoxysilane partial hydrolyzate obtained after the partial hydrolysis had a molecular weight of 1,200.

Next, 1% ammonia water was added to this reaction mixture to
After adjusting to H6, 30 g of dimethyldimethoxysilane, 170 g of methyltrimethoxysilane, and 54 g of water were added with stirring and kept at 50° C. for 3 hours to prepare a coating solution for forming a silica-based film.

Example 5 Methyl silicate-51118g used in Example 3,
72 g of water and 491 g of propylene glycol monopropyl ether were mixed and stirred, and concentrated nitric acid was added to adjust the pH to 2.
Adjusted to. The resulting mixture was kept at 50°C for 1 hour,
Partial hydrolysis of tetramethoxysilane was carried out. The condensation product of the alkoxysilane partial hydrolyzate obtained after the partial hydrolysis had a molecular weight of 1000.

Next, 1% monoethanolamine was added to this reaction mixture to adjust the pH to 7, and then 205 g of methyltrimethoxysilane and 54 g of water were added with stirring, and the mixture was heated at 50°C.
The mixture was kept for 1 hour to prepare a coating solution for forming a silica-based film.

Example 6 In order to compare the pot lives of the coating solutions obtained in Examples 1 to 5, the viscosity of each coating solution was measured immediately after preparation and after storage for one month.

In addition, storage was placed in a constant temperature bath at 25°C.

Viscosity is the value at 25°C.

The results are shown in Table 1.

Comparative Example 1 While mixing and stirring 28,357 g of ethyl silica, 240 g of water, and 403 g of ethanol, the pH was adjusted to 1 by adding concentrated nitric acid. The resulting mixture was heated to 50℃ for 1
Tetraethoxysilane was partially hydrolyzed for a certain period of time to prepare a coating solution for forming a silica film. The condensation product of the alkoxysilane partial hydrolyzate contained in this coating liquid had a molecular weight of 1,500.

Comparative Example 2 30 g of dimethyldimethoxysilane, 170 g of methyltrimethoxysilane, and 51118 g of methyl silicate
After mixing and stirring with 126 g of water, acetic acid was added to adjust the pH to 4, and the mixture was kept at 50°C for 10 hours to partially hydrolyze the alkoxysilane to prepare a coating solution for forming a silica-based film. did. The condensation product of the alkoxysilane partial hydrolyzate contained in this coating solution has a molecular weight of 220.
It was 0.

The coating liquids obtained in the above Examples and Comparative Examples were applied onto a silicon wafer using a spinner at 400 Orpm.
After drying at 50°C for 10 minutes, drying at 800°C for 30 minutes in nitrogen
Fired separately. The thickness of the obtained SiO□ film was 1,100 to 2,500 as shown in Table 1, and no cracks were observed. Table 2 shows the dielectric constant and etch rate of these films.

Surface etch rate: HF aqueous solution (HF 5cc/820
The etching rate was calculated from the change in the film thickness after 5 minutes of immersion in No. 1 and the change in the film thickness before immersion.

As can be seen from Table 2, the dielectric constant is low. Furthermore, the etch rate value is also small. That is, a dense film is formed.

Next, the coating liquids obtained in Examples (4), (5) and Comparative Example (2) were applied to A with a line and space pitch of 2 μm.
It was applied onto a silicon wafer provided with I wiring by a spin code method and dried at 150° C. for 15 minutes. Next, it was baked at 450° C. for 30 minutes in nitrogen to form a silica-based insulating film. The thickness of this silica-based insulating film was 5000 mm.

Furthermore, on this film, a thickness of 2,000 people was coated using the CVD method.
An interlayer insulating film was formed by applying a jO2 film.

A 0.8 μm contact hole was formed in this interlayer insulating film by dry etching using the RIE method, and then a second layer of A1 wiring was formed by sputtering to create a two-layer A1 wiring element. Upper and lower A1 of the element thus obtained
The contact resistance between interconnects and the dielectric constant of the interlayer insulating film were measured. Table 3 shows the results.

Table 3 From Table 3, the silica-based insulating film formed as described above has a low contact resistance because there is no oxidation of the AI wiring due to zero resorption and desorption of water. It also has a low dielectric constant.

[Brief explanation of drawings]

1 to 3 are cross-sectional views of a semiconductor device provided with a silica-based insulating film according to the present invention.

Claims (2)

[Claims] (1) General formula R^1_nSi(OR^2)_4_-_n
(In the formula, R^1 is a hydrocarbon group, and R^2 is a carbon number of 1
-4 alkyl group, n is 0 to 3) is partially hydrolyzed in the presence of an organic solvent, water and an acid, and then the obtained portion is A coating solution for forming a silica film containing a condensation product of a partial hydrolyzate of an alkoxysilane obtained by contacting a hydrolysis solution with an alkali is applied onto a semiconductor substrate and then heated to form a silica insulating film. 1. A method of manufacturing a semiconductor device, comprising the step of providing on a semiconductor substrate. (2) General formula R^1_nSi(OR^2)_4_-_n
(In the formula, R^1 is a hydrocarbon group, and R^2 is a carbon number of 1
-4 alkyl group, n is 0 to 3) is partially hydrolyzed in the presence of an organic solvent, water and an acid, and then the obtained portion Contacting the hydrolyzed solution with an alkali,
A coating solution for forming a silica-based film containing a condensation product of a partial hydrolyzate of alkoxysilane made acidic by adding an acid to the obtained coating solution is applied onto a semiconductor substrate, and then heated.
A method for manufacturing a semiconductor device, comprising the step of providing a silica-based insulating film on a semiconductor substrate.