JP2002038091A - Silica-based coating film and semiconductor device having the silica-based coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silica-based coating film excellent in adhesive properties (particularly, adhesive properties in the CMP process) and a semiconductor device which causes less delay of signals and is of a high quality and a high reliability. SOLUTION: There are provided a silica-based coating film of which the surface has a critical surface tension of 29×10-3 N/m or more, and which is formed by coating and drying a coating fluid for forming the silica-based coating film comprising a polysiloxane, which has a substituting group having an unsaturated bond and a substituting group having no unsaturated bond, and an organic solvent, and a semiconductor device in which the silica-based coating film is used as an interlaminar insulating film for multilayer interconnection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a silica-based coating and a semiconductor device having the silica-based coating.

[0002]

2. Description of the Related Art With the miniaturization of wiring due to the increase in the speed of LSIs, an increase in signal delay time due to an increase in capacitance between wirings has become a problem. Conventionally, C having a relative dielectric constant of about 4.2
Although the SiO ₂ film formed by the VD method has been used as an interlayer silica-based film, the capacitance between devices has been reduced, and LSI
In order to improve the operation speed of the device, a film having a lower dielectric constant is required.

[0003] As a low dielectric constant film which is currently put into practical use, SiO 2 formed by a CVD method having a relative dielectric constant of about 3.5 is used.
F film. Organic SOG (Spin On Glass), organic polymers, and the like have been actively studied as silica-based coatings having a relative dielectric constant of less than 3.5.

[0004] With the development of multilayer wiring of LSI, CMP (Chemical Mechanical Polishing) has been used for global flattening.
Is becoming mandatory. In order to cope with this CMP process, low dielectric constant characteristics, mechanical strength and adhesion to an adjacent film are required as important characteristics for a silica-based film. Organic SOG and organic polymer which have been variously studied as a low dielectric constant film having a relative dielectric constant of less than 3.5 are formed of Si formed by a CVD method.
Although the relative dielectric constant is lower than that of the O ₂ film and the SiOF film, the adhesiveness between the film and the adjacent film is low, and there is a problem that the insufficient adhesiveness causes separation between the silica-based film and the upper film in the CMP process. .

[0005]

SUMMARY OF THE INVENTION The first aspect of the present invention provides a silica-based coating having excellent adhesiveness (particularly, adhesiveness in a CMP step). The invention described in claim 2 has the effects of the invention described in claim 1 and provides a silica-based coating having more excellent adhesion. The invention according to claim 3 has the effect of the invention according to claim 1 or 2,
Further, the present invention provides a silica-based coating excellent in low dielectric constant. A fourth aspect of the present invention is to provide a high-quality, high-reliability semiconductor device with little signal delay.

[0006]

The present invention provides a coating solution for forming a silica-based film, comprising a polysiloxane having a substituent having an unsaturated bond and a substituent having no unsaturated bond, and an organic solvent. The present invention relates to a silica-based coating having a critical surface tension of 29 × 10 ⁻³ N / m or more, which is applied and dried.
The present invention also relates to the silica-based coating, wherein the substituent having an unsaturated bond is a vinyl group. Also, the present invention
The present invention relates to the silica-based coating having a relative dielectric constant of 3.0 or less. The present invention also relates to a semiconductor device using the above-mentioned silica-based coating as an interlayer insulating film of a multilayer wiring.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A silica-based coating film according to the present invention is a coating solution for forming a silica-based coating film comprising a polysiloxane having a substituent having an unsaturated bond and a substituent having no unsaturated bond, and an organic solvent. Is applied and dried, and the critical surface tension of the surface must be 29 × 10 ⁻³ N / m or more.

In the present invention, the coating solution for forming a silica-based film containing a polysiloxane having a substituent having an unsaturated bond and a substituent having no unsaturated bond and an organic solvent is preferably a hydrolytic condensation of alkoxysilane. Compositions can be used.

The substituent having an unsaturated bond includes:
For example, alkenyl groups such as vinyl group, allyl group, cyclohexenyl group, methacryloxy group, and methacryloxypropyl group; alkynyl groups such as ethynyl group and 5-hexenyl group; aryl groups such as phenyl group and tolyl group; −
Acryloxypropyl group, methacryloxypropyl group,
Substituents containing a carbonyl such as an acetate group are exemplified. Among them, alkenyl groups are preferred, and vinyl and allyl groups are more preferred, and vinyl group is particularly preferred, from the viewpoints of adhesiveness, low dielectric constant, and the like. These can be present alone or in combination of two or more.

Examples of the substituent having no unsaturated bond include, for example, an alkyl group having 1 to 18 carbon atoms and a C 1 to C 1 group.
18 aryl groups. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and an octadecyl group. Examples of the aryl group include a phenyl group, a tolyl group, and a naphthyl group. Among them, a methyl group and a phenyl group are preferred, and a methyl group is more preferred, from the viewpoints of adhesiveness, low relative permittivity, and the like. These can be present alone or in combination of two or more.

The hydrolysis-condensation composition of the alkoxysilane may be, for example, an organic solvent containing an alkoxysilane having a substituent having an unsaturated bond and an alkoxysilane having a substituent having no unsaturated bond. It can be produced by a known method in which water is added in the presence of an organic solvent and, if necessary, a catalyst to carry out a hydrolytic condensation reaction. In this case, heating may be performed if necessary.

The alkoxysilanes having a substituent having an unsaturated bond include, for example, vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, allyltriethoxysilane and the like.
These are used alone or in combination of two or more.

The above-mentioned alkoxysilanes having a substituent having no unsaturated bond include, for example, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, tetramethoxysilane, tetraethoxysilane And the like.
These are used alone or in combination of two or more.

Examples of the catalyst include inorganic acids such as hydrochloric acid, nitric acid and sulfuric acid, and organic acids such as formic acid, oxalic acid, acetic acid and maleic acid.

Examples of the organic solvent include alcohol solvents such as methanol, ethanol, propanol and butanol, methyl acetate, ethyl acetate, propyl acetate, and the like.
Acetate solvents such as butyl acetate; glycol acetate solvents such as ethylene glycol monomethyl acetate and ethylene glycol diacetate; N-methyl-2
Examples include amide solvents such as pyrrolidone, glycol ether solvents, and lactone solvents such as γ-butyrolactone, and these are used alone or in combination of two or more.

The polysiloxane produced by the hydrolysis-condensation reaction has a weight-average molecular weight (gel permeation chromatograph) in view of compatibility with a heat-decomposable polymer described later, solubility in an organic solvent, mechanical properties, moldability and the like. (A value measured by a chromatography (GPC) and converted using a standard polystyrene calibration curve) is preferably from 500 to 20,000, and more preferably from 1,000 to 10,000.

Further, in the hydrolysis-condensation composition containing the synthesized polysiloxane, if necessary, water present in the system may be removed by distillation or the like, and the catalyst may be removed with an ion exchange resin or the like.

The silica-based coating of the present invention can be prepared, for example, by coating a coating liquid (hydrolysis-condensation composition) for forming a silica-based coating on a silicon wafer or metal substrate by dipping, spraying, screen printing, spin coating, or the like. , Applied on a substrate such as a ceramic substrate, and dried by heating in air or an inert gas such as nitrogen at 60 to 600 ° C. for about 10 seconds to 2 hours to remove an organic solvent. be able to.

The thickness of the silica-based coating is not particularly limited, but is preferably 0.01 to 10 μm, more preferably 0.05 to 5 μm, and more preferably 0.1 to 5 μm from the viewpoint of crack resistance and the like. It is particularly preferred that the thickness be 3 μm.

The critical surface tension of the surface of the silica-based coating in the present invention is 2 points from the viewpoint of exhibiting good adhesion between the silica-based coating and the film formed thereon in the CMP step.
It needs to be 9 × 10 ⁻³ N / m or more. If the critical surface tension exceeds 60 × 10 ⁻³ N / m, the dielectric constant tends to increase, and the film properties tend to decrease due to an increase in desorbed gas components.

The critical surface tension of the surface of the silica-based coating is 29
Adjusting to at least 10 ^-3 N / m can be performed, for example, by adjusting the type and amount of the alkoxysilane used.

In the present invention, the critical surface tension is determined by dropping a liquid having several different surface tensions onto a solid surface, measuring the contact angle (θ) of the droplet, and determining the surface tension of the liquid (horizontal axis).
After plotting cosθ value (vertical axis), surface tension and cosθ
A straight line equation is obtained from the values, and this straight line is expressed as cos θ = 1 (θ =
This is the value when extrapolated to 0).

The critical surface tension is a measure of the wetting characteristics of a solid surface and is defined as a characteristic value when the solid surface is completely wetted. It is said that a solid surface having a high critical surface tension is easily wettable by many liquids, and a small solid surface is hardly wettable by many liquids ("Adhesion Handbook" edited by The Japan Adhesion Association, 2nd edition, P20-P49) .

Here, the contact angle can be easily measured with a commercially available device called a contact angle measuring device. Further, the critical surface tension can be calculated from the following equation so as to obtain cos θ = 1 after plotting the surface tension of the liquid and the cos θ value and determining the slope and intercept of the straight line by the least square method.

[0025]

X = (Y−b) / a [dyn / cm = 10 ⁻³ N / m] Y: cos θ = 1 X: surface tension value [dyn / cm] a: slope of straight line b: intercept of straight line

Examples of the above-mentioned liquids having different surface tensions include water, hydrogen-bonded liquids such as glycerin, formamide, ethylene glycol, propylene glycol and isopropyl alcohol, and hydrocarbons such as n-hexane and n-decane. A liquid or the like can be used.

The silica-based coating of the present invention is suitable as an interlayer insulating film in electronic components such as semiconductor devices and multi-chip module multilayer wiring boards. In semiconductor devices, a surface protective film, a buffer coat film, an interlayer insulating film, etc. Can be used as

[0028]

The present invention will be described below with reference to examples. In the following, Vi represents a vinyl group (CH ₂ ＣＨCH—)
Represents

Example 1 89 g of CH ₃ Si (OCH ₂ CH ₃ ) ₃ and ViSi (OCH ₂
90 g of CH ₃ ) ₃ were dissolved in 200 g of propylene glycol monopropyl ether, and 54 g of water and 0.1 g of nitric acid were added thereto.
After dropping 1 g of the mixture in 1 hour, the mixture was further added at room temperature for 24 hours.
The reaction was carried out for a period of time to obtain a coating liquid for forming a silica-based film (hydrolysis-condensation composition).

The coating solution was applied for 2000 mi using a spinner.
After coating on a 6-inch silicon wafer at n- ¹
Each one on a hot plate controlled at 0 ° C and 250 ° C
After drying in an electric furnace at 400 ° C. for 1 hour in nitrogen, a colorless, transparent and crack-free film was obtained. The thickness of this film was measured and found to be 0.50 μm.

An aluminum coating of 0.1 μm on this coating
Was formed by a sputtering method, and the dielectric constant of the sample was measured at a frequency of 1 MHz using an LF impedance meter.
It was 0.

Next, the critical surface tension of this silica-based coating was calculated. Critical surface tension is measured by placing the droplets of water, glycerin, formamide, ethylene glycol and propylene glycol on a silica-based coating, measuring the respective contact angles, calculating cosθ, and plotting the surface tension of the liquid and cosθ. Cosθ = 1 from the straight line formula by the least squares method
Extrapolated to

Further, an SiO ₂ film was formed on the silica-based coating under a plasma atmosphere, and a cross-cut tape peeling test (J
According to IS K5400), the adhesion between the silica-based coating and the upper SiO ₂ film was evaluated. The results are shown in Table 1.

Comparative Example 1 142 g of CH ₃ Si (OCH ₂ CH ₃ ) ₃ and ViSi (OC
38 g of H ₂ CH ₃ ) ₃ was dissolved in 200 g of propylene glycol monopropyl ether, and a mixed solution of 54 g of water and 0.1 g of nitric acid was added dropwise for 1 hour, followed by reaction at room temperature for 24 hours to form a silica-based film. Coating solution.

Thereafter, the film thickness is set to 0.50 in the same manner as in the first embodiment.
A colorless, transparent and crack-free coating having a thickness of μm was obtained, and each characteristic was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 178 g of CH ₃ Si (OCH ₂ CH ₃ ) ₃ was dissolved in 400 g of propylene glycol monopropyl ether, and a mixed solution of 50 g of water and 0.1 g of nitric acid was added dropwise over 1 hour. For 24 hours to obtain a coating solution for forming a silica-based film.

Thereafter, the film thickness is set to 0.50 in the same manner as in the first embodiment.
A colorless, transparent and crack-free coating having a thickness of μm was obtained, and each characteristic was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0038]

[Table 1]

<< Evaluation Criteria for Cross Cut Tape Test >> ◎ No peeling at all ○ The number of peels within 100 cross cuts is within 10 △ The number of peels within 100 cross cuts is within 10-49 × 100 cross cuts Of which 50 or more are peeled off

[0040]

The silica coating according to the first aspect is excellent in adhesiveness (particularly, adhesiveness in a CMP step). The silica-based coating according to the second aspect has the effect of the silica-based coating according to the first aspect, and is more excellent in adhesiveness. The silica-based coating according to the third aspect has the effect of the silica-based coating according to the first or second aspect, and is further excellent in low dielectric constant. The semiconductor device according to claim 4 is of high quality and low in reliability with little signal delay.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H01L 21/768 H01L 21/90 Q (72) Inventor Shigeru Nobe 4-3-1-1, Higashicho, Hitachi City, Ibaraki Prefecture No. Hitachi Chemical Industry Co., Ltd. Yamazaki Plant (72) Inventor Kazuhiro Enomoto 4-3-1 Higashicho, Hitachi City, Ibaraki Prefecture Hitachi Chemical Co., Ltd. Yamazaki Plant F term (reference) 4J038 DL031 DL111 DL121 KA06 MA11 NA11 NA17 NA21 PB09 PB11 PC02 PC03 PC08 5F033 HH08 QQ48 RR04 RR25 SS15 SS22 XX12 XX24 5F058 AA08 AB10 AC03 AF04 AF06 AG01 AH02

Claims (4)

[Claims] 1. A surface obtained by applying and drying a coating solution for forming a silica-based film comprising a polysiloxane having a substituent having an unsaturated bond and a substituent having no unsaturated bond and an organic solvent. Is a silica-based coating having a critical surface tension of 29 × 10 ⁻³ N / m or more. 2. The silica-based coating according to claim 1, wherein the substituent having an unsaturated bond is a vinyl group. 3. The silica-based coating according to claim 1, which has a relative dielectric constant of 3.0 or less. 4. A semiconductor device using the silica-based coating according to claim 1, 2 or 3 as an interlayer insulating film of a multilayer wiring.