JPH0353529A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent such defects as a pinhole or a void from occurring by decreasing specific dielectric constant by a method wherein a silica base insulating film in specific relative permittivity having specified value is provided. CONSTITUTION:Wiring layers 13 are provided on a silicon substrate, etc., through the intermediary of the first insulating film 12 such as thermal oxide film while an interlayer insulating film 14 is provided on these wiring layer 13. A silicon base insulating film 15 is provided on the interlayer insulating film 14 while this silicon base insulating film 15 is formed to flatten the surface of the interlayer insulating film 14 as well as to further form the second wiring layer 16 on the film 15. The relative permittivity of the second silica base insulating film 15 formed on a semiconductor device is to be 3.0-4.5.

Description

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

TECHNICAL BACKGROUND OF THE INVENTION AND PROBLEMS THEREOF 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, and a silica insulating film 15 is formed on this interlayer R film 14 to planarize the insulating film 14. Further, if necessary, a second layer is formed on the silica insulating film 15.
After depositing the interlayer insulating film 16, a second wiring layer (not shown) is formed.

The above-mentioned silica-based insulating film 15 has conventionally been obtained by applying a coating liquid prepared by dissolving or dispersing an organosilicon compound such as silanol in alcohol by a so-called SOG method (Spin on Glass method) such as a spin coating method. It was formed by heating and curing the coated film (SOG film).

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

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

Furthermore, in a semiconductor device having multilayer wiring as described above,
In particular, during etching to open through holes and form the second wiring layer, wiring such as aluminum in the wiring layer may be oxidized to aluminum oxide, etc., increasing the resistance value and causing poor conductivity. there were.

It is presumed that such poor conductivity in the wiring layer occurs because the silica-based insulating film contains re-adsorbed moisture, and this moisture oxidizes the wiring, producing insulating Ag203. be done.

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 a semiconductor device of 1 Mega or more, when the diameter of the through hole is 1 μm and the dielectric constant of the adjacent insulating film increases, the impedance of the AfI 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. The object of the present invention is to provide a semiconductor device provided with a silica insulating film that has excellent properties, mechanical strength, chemical resistance, moisture resistance, etc., and a method for manufacturing the same.

Summary of the Invention A semiconductor device according to the present invention has a dielectric constant of 3.0 to 4.5.
A silica-based insulating film is provided on a semiconductor substrate.

Further, the method for manufacturing a semiconductor device according to the present invention includes (where R
1 is a hydrocarbon group, R2 is an alkyl group having 1 to 4 carbon atoms, and n is O to 3) is partially hydrolyzed in the presence of an organic solvent, water, and an alkali catalyst. Then, the obtained partial hydrolysis solution is further partially hydrolyzed in the presence of water and an acid catalyst to obtain a coating solution for forming a silica-based film system containing a condensate of an alkoxysilane partial hydrolysis product. The silica-based insulating film is coated on the semiconductor substrate and then heated to provide a silica-based insulating film on the semiconductor substrate.

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

In the semiconductor device according to the present invention, for example, as shown in FIG.
A wiring layer 13 is provided via an insulating film 12, and 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 .
This is a film for flattening the surface and forming a second wiring layer (not shown) thereon.

The silica-based insulating film formed in the semiconductor device of the present invention has a dielectric constant of 3.0 to 4.5, preferably 3.0 to 4.0. If the relative dielectric constant of this silica-based insulating film exceeds 4.5, the above-mentioned problems will become noticeable and speeding up of semiconductor devices will be hindered.

Further, if it is lower than 3.0, other properties of the coating will be impaired, which is not preferable.

In addition, this silica-based insulating film has hydrogen fluoride in 1 g of water.
The etching rate (human limit) 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 25λ or less, preferably 20^ or less. This is desirable.

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 according to the present invention, the second wiring layer can also be formed directly on the silica-based insulating III 15, as shown in FIG.

Furthermore, in the semiconductor device according to the present invention, as shown in FIG. The silica-based insulating film 15 may be formed as an interlayer insulating film. In this case, the second interlayer insulating film 16 may be omitted.

Furthermore, in the semiconductor device according to the present invention, the first insulator 11i112 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 coated on the substrate on which the wiring layer is formed.

This coating liquid for forming a silica-based film is I (in the formula, R is a hydrocarbon group, and R2 has a carbon number of 1 to 4
(n is an alkyl group of 0 to 3) is partially hydrolyzed in the presence of an organic solvent, water and an alkali catalyst, and then the resulting partially hydrolyzed solution is treated with water and an acid catalyst. prepared by further partial hydrolysis in the presence of

The alkoxysilane used in the present invention is l (wherein R is a hydrocarbon group and R2 has 1 to 4 carbon atoms.
is an alkyl group, and n is 1 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, dimethyldiethoxysilane, monoethyltrimethoxysilane, and monoethyltrimethoxysilane. Ethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, 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, propanol, and butanol, ethylene glycol ethers such as methyl cellosolve and ethyl cellosolve, ethylene glycol, and propylene glycol. Glycols such as, ester acids such as methyl acetate, ethyl acetate, and methyl lactate are used.

These organic solvents may be used alone or in combination.

As the alkali catalyst, specifically, a compound showing alkalinity in an aqueous solution such as ammonia, amine, metal hydroxide such as sodium hydroxide, potassium hydroxide, calcium hydroxide, etc. is used.

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

At this time, the alkoxysilane is S t O
It is desirable that the amount of 2 is used in an 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 Si-OR group of the alkoxysilane. The amount of water is S i-OR group 1 of alkoxysilane
When the amount is less than 0.1 mol, the hydrolysis angle of the alkoxysilane tends to be insufficient, while when it exceeds 2 mol, the hydrolysis rate of the alkoxysilane becomes too fast, and the alkoxysilane is This tends to make it difficult to control the degree of polycondensation.

The alkaline catalyst is desirably used in an amount such that the pH of the reaction mixture is 6-12, preferably 7-10. The higher the pH of the reaction mixture, the faster the rate of hydrolysis of the alkoxysilane, the amount of water added can be reduced, and the rate of partial hydrolysis can be lowered.

The partial hydrolysis reaction of alkoxysilane is 10 to 100
It is desirable to carry out the reaction at a temperature of preferably 20 to 60°C. Further, the above reaction time varies greatly depending on the reaction temperature, but is usually about 0.5 to 5 hours, preferably about 1 to 3 hours.

When the partial hydrolysis reaction of alkoxysilane is carried out in the presence of an alkali catalyst as described above, the alkoxysilane is partially hydrolyzed and a condensation product of a partially hydrolyzed alkoxysilane is produced. The molecule Il (polystyrene equivalent molecular weight) of this condensation product is preferably 100 to 5,000, preferably 500 to 2,000.

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 final silica-based coating, resulting in a dense coating. There is a tendency not to
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,
An acid catalyst is added to the reaction mixture obtained by partial hydrolysis H L in the presence of water and an alkali catalyst to partially hydrolyze the remaining alkoxysilane.

As the acid catalyst, specifically, inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid, and organic acids such as acetic acid and oxalic acid are used.

The acid catalyst is used when the pH of the reaction mixture is 0 to 6. Preferably 1~
It is used in an amount such that 5.

Since the partial hydrolysis reaction of alkoxysilane becomes faster as the pH decreases, it is preferable to appropriately control the pH of the reaction system, the amount of water, and the partial hydrolysis temperature.

When partially hydrolyzing an alkoxysilane in the presence of an acid catalyst as described above, water may be added to the reaction mixture as necessary, or fresh alkoxysilane may be added.

The acid-catalyzed partial hydrolysis reaction of alkoxysilane is
It is desirable to conduct the reaction at a temperature of 10 to 100°C, preferably 20 to 60°C. Further, the above reaction time varies greatly depending on the reaction temperature, but is usually about 0.5 to 5 hours, preferably about 1 to 3 hours.

When alkoxysilane is partially hydrolyzed in the presence of an alkali catalyst and then partially hydrolyzed in the presence of an acid catalyst in this way, a silica-based film containing a condensation product of the alkoxysilane partial hydrolyzate can be formed. This coating solution is applied onto a semiconductor substrate.
Next, by drying and baking, a film is formed on the substrate. The molecular weight of the condensation product of the alkoxysilane partial hydrolyzate is usually 100 to 10.000, preferably 50.
It is desirable that it is 0 to 5,000. In addition, in order to apply the coating liquid onto the substrate, spray method, subin coating method,
Conventional methods such as dip coating, roll coating, screen printing, and transfer printing can be used.

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

The silica-based coating formed using the coating liquid for forming a silica-based coating as described above has a dielectric constant of 3.0 to 4.5, preferably 3.0 to 4.0. Further, the etching rate of this silica-based film is desirably 25 μm/min or less, preferably 20 μm/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. Is the present invention a dense silica system like the one mentioned above? 11m is obtained by partially hydrolyzing alkoxysilane in the presence of an alkali catalyst and then an acid catalyst to obtain a coating film with a low content of organic residues. This is thought to be because the generation of voids caused by decomposition of residues is suppressed.

For example, in the case of the insulating film 12 formed on a semiconductor substrate, the thickness of the silica-based film formed in the present invention is usually 1.00 mm.
It is about 0 to 2,000λ, but in the case of interlayer insulation film, it is about 5
There may be cases where a silica-based coating having a thickness of 000λ or more is required. In such a case, it is preferable to use a mixture of a tetraalkoxysilane and a trialkoxysilane such as monomethyltrimethoxysilane or a dialkoxysilane such as dimethyldimethoxysilane as the alkoxysilane. In order to obtain a silica-based coating having a thickness of less than 5000λ, it is preferable to use a tetraalkoxysilane such as tetramethoxysilane or tetraethoxysilane as the alkoxysilane.

Tetraalkoxysilane and trialkoxysilane or dialkoxysilane may be used as a mixture from the beginning, and for example, the partial hydrolysis step using an alkali catalyst is performed using only the tetraalkoxysilane, and the partial hydrolysis step using an acid catalyst is performed using only the tetraalkoxysilane. Trialkoxysilane or dialkoxysilane may be added during the process.

The mixing ratio of tetraalkoxysilane and trialkoxysilane or dialkoxysilane is 0.5-4.5:5-920-2 (weight as Sto2). ratio) is desirable.

When the amount of tetraalkoxysilane increases, the resulting silica-based coating has excellent heat resistance and moisture resistance, but when forming a silica-based corrugated film with a thick film thickness, cracks tend to occur easily. When the amount of trialkoxysilane or dialkoxysilane increases, 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 1 357 g of tetraethoxysilane (ethyl silica manufactured by Tama Chemical Industry Co., Ltd.) -28.S i 02 equivalent tetraethoxysilane concentration 28% by weight), 120 g of water, and IPA
523 g was mixed and stirred, and then 1% NH3 water was added to adjust the pH to 8. The resulting mixture was kept at 50° C. for 1 hour to partially hydrolyze tetraethoxysilane. The condensation product of the alkoxysilane partial hydrolyzate obtained after the partial hydrolysis had a molecular weight of 800 in terms of boristyrene.

Next, concentrated nitric acid was added to this reaction mixture to adjust the pH to 2, and the mixture was kept at 30°C for 12 hours to further partially hydrolyze tetraethoxysilane to prepare a silica-based arytenoid coating liquid. .

Example 2 250 g of tetraethoxysilane (ethyl silicate manufactured by Tama Chemical Industry - 40.3 I O2 equivalent tetraethoxysilane concentration 40% by weight), 60 g of water, and 690 g of ethyl cellosolve were mixed and stirred, and 1% monoethanol was added. Amine was added to adjust pH to 9. 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 500.

Concentrated hydrochloric acid was then added to the reaction mixture to adjust the pH to 1, and the mixture was kept at 50° C. for 2 hours to further partially hydrolyze tetraethoxysilane to prepare a silica-based film coating solution.

Example 3 98 g of tetramethoxysilane (manufactured by Tama Chemical Industry Co., Ltd., methyl silicate-51.8 1 02 equivalent tetramethoxysilane concentration 5L weight %), 90 g of water, and 812 g of propylene glycol monopropyl ether were mixed and stirred,
Triethanolamine was added to adjust pH to 7. 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 2,000.

Next, phosphoric acid was added to this reaction mixture to adjust the pH to 2, and the mixture was kept at 30° C. for 1 hour to further partially hydrolyze the tetratoxysilane, thereby preparing a coating solution for forming a silica-based film.

Example 4 Methyl silicate-51118g used in Example 3,
Water 72. and 556 g of ethyl cellosolve were mixed and stirred, and the pH was adjusted to 7 by adding 1% NH3 water. 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, acetic acid was added to this reaction mixture to adjust the pH to 4, and then 30 g of dimethyldimethoxysilane, 170 g of methyltrimethoxysilane, and 54 g of water were added with stirring, and the mixture was kept at 50°C for 3 hours to further add the alkoxysilane. Partial hydrolysis M was carried out 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 monobrobyl ether were mixed and stirred, and the pH was adjusted to 7 by adding 0.1% NH3 water.

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 1000.

Next, acetic acid was added to this reaction mixture to adjust the pH to 5, and then 205 g of methyltrimethoxysilane and 54 g of water were added.
were added with stirring, kept at 50° C. for 1 hour, and the alkoxysilane was further partially hydrolyzed to prepare a coating solution for forming a silica-based film.

Comparative Example 1 28,357 g of ethyl silica, 240 g of water, and 403 g of ethanol were mixed.While stirring, concentrated nitric acid was added to adjust the pH to 1. The resulting mixture was heated to 50°C.
The mixture was kept for 1 hour to partially hydrolyze the tetraethoxysilane, thereby preparing 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 methyl silicate-51 1
18 g and 126 g of water were mixed and stirred, 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.
A silica-based coating solution was prepared. The condensation product of alkoxysilane partial hydrolyzate contained in this coating solution is
The molecular weight was 2200.

The coating liquids obtained in the above Examples and Comparative Examples were applied onto a silicon wafer using a spinner at 4000 rpm.
After drying at 150°C for 10 minutes, drying at 800°C in nitrogen for 3
Baked for 0 minutes. The thickness of the obtained S502 film is shown in Table-
As shown in No. 1, it was 1100 to 250 OA, and no cracks were observed. Table 1 shows the dielectric constant and etch rate of these films.

Table-1 Etch rate: HF aqueous solution (HF5cc/H20IN)
The etching rate was calculated from the change in the film thickness after 5 minutes of immersion and the change in the film thickness before immersion.

As can be seen from Table 1, 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 by spin coating onto a silicon wafer provided with l wiring, and dried at 150° C. for 15 minutes. Next, a silica-based insulating film was formed by baking in nitrogen at 450° C. for 30 minutes. The thickness of this silica-based insulating film was 5000 mm.

Furthermore, on this film, a 2000 mm thick S
An interlayer insulating film was formed by applying an iO2 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 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 wiring and the dielectric constant of the interlayer insulating film are 81
It was fixed at 1. The results are shown in Table 2 below.

Table 2 From Table 2, it can be seen that the silicate insulating film formed as described above has a low contact resistance due to the desorption of re-adsorbed moisture, since there is no oxidation of the wiring. 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) A semiconductor device characterized in that a silica-based insulating film having a dielectric constant of 3.0 to 4.5 is provided on a semiconductor. (2) General formula R^1_nSi(OR^2)_4_-_
n (in the formula, R^1 is a hydrocarbon group, R has 1 to 1 carbon atoms)
is an alkyl group of 4, and n is 0 to 3), one or more alkoxysilanes represented by
A condensation product of an alkoxysilane partial hydrolyzate obtained by partial hydrolysis in the presence of water and an alkali catalyst, and then further partial hydrolysis of the obtained partial hydrolysis liquid in the presence of water and an acid catalyst. A method for manufacturing a semiconductor device, comprising the step of applying a silica-based film-forming coating liquid contained therein onto a semiconductor substrate and then heating it to form a silica-based insulating film on the semiconductor substrate.