JP2000272915A - Coating solution for forming silica-based coating film, production of silica-based coating film, silica-based coating film and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating solution for formation of silica-based coating film capable of producing a silica-based coating film having good film-forming property and low dielectric constant and provide a method for producing the silica-based coating film and a semiconductor device having the silica-based coating film and high reliability. SOLUTION: This coating solution for formation of a silica-based coating film comprises (A) a polysiloxane containing >=20 wt.% polymer having >=10,000 molecular weight and produced by subjecting an alkoxysilane compound represented by the formula R1nSi(OR2)4-n [R1 is a 1-6C alkyl group or a 6-10C aryl group and plural R1 may be same or different and R2 is a 1-10C alkyl group and plural R2 may be same or different and (n) is an integer of 0-2] and (B) a solvent. This method for producing the silica-based coating film comprises applying the coating solution for formation of the silica-based coating film onto a substrate, drying the solution at 50-350 deg.C and heating and curing the dried coating film at 200-600 deg.C under nitrogen atmosphere. This semiconductor device has the silica-based coating film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating solution for forming a silica-based coating, a method for producing a silica-based coating, a silica-based coating, and a semiconductor device. The present invention relates to a method for producing a silica-based coating using the same, a silica-based coating, and a semiconductor device.

[0002]

2. Description of the Related Art Conventionally, as a method for interlayer insulation of semiconductor elements such as ICs and LSIs, Si is formed on a substrate having a patterned wiring layer by a vapor deposition method such as vacuum deposition or CVD.
Forming a first interlayer insulating film made of O ₂ , SiN or the like;
An SOG (Spin on Glass) liquid (comprising an organosiloxane oligomer solution) is spin-coated on the second layer, and then heat-treated to form an organosiloxane-based film. Next, an SOG planarization process using a three-layer interlayer film in which a third interlayer insulating film is formed in the same manner as the first layer is widely used.

In recent years, as the speed of ICs, LSIs, and the like has increased, the dielectric constant of interlayer materials has been proposed to be reduced. However, interlayer films having good film-forming properties and a sufficiently low dielectric constant have been proposed. At present, an organosiloxane oligomer capable of forming the following has not been obtained yet.

[0004]

SUMMARY OF THE INVENTION The first aspect of the present invention provides a coating solution for forming a silica-based film, which can produce a silica-based film having good film-forming properties and a low dielectric constant. The second aspect of the present invention is to provide a method for producing a silica-based coating film which can easily produce a silica-based coating film having good film formability and a low dielectric constant with a high yield. The third aspect of the present invention provides a silica-based coating having good film uniformity and a low dielectric constant. The fourth aspect of the present invention is to provide a highly reliable semiconductor device having a silica-based coating having a good film uniformity and a low dielectric constant.

[0005]

The present invention relates to (A) a compound represented by the general formula (I):

Embedded image (Wherein R ¹ is an alkyl group having 1 to 6 carbon atoms or 6 carbon atoms)
Represents an aryl group of 10 to 10, a plurality of R ¹ may be the same or different, R ² represents an alkyl group having 1 to 10 carbon atoms, and a plurality of R ² may be the same or different , N is an integer of 0 to 2) represented by the following formula:
The present invention relates to a coating solution for forming a silica-based film, comprising a polysiloxane containing 20% by weight or more of a polymer of 0.000 or more and (B) a solvent.

Further, the present invention provides a silica-based coating obtained by applying the above-mentioned coating solution for forming a silica-based coating on a substrate, drying the coating at 50 to 350 ° C., and then heating and curing at 200 to 600 ° C. in a nitrogen atmosphere. A method for producing the same. The present invention also relates to a silica-based coating obtained by the above-mentioned production method. The present invention also relates to a semiconductor device having the above-mentioned silica-based coating.

[0007]

DETAILED DESCRIPTION OF THE INVENTION In the general formula (I), the number of carbon atoms is 1 to 1.
As the alkyl group of 6, for example, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec
-Butyl group, tert-butyl group, pentyl group, isoamyl group, hexyl group, and the like. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, and an n-butyl group. Group, sec-butyl group, t
ert-butyl group, pentyl group, isoamyl group, hexyl group, heptyl group, octyl group, 2-ethylhexyl group,
Nonyl group, decyl group, norbornyl group, bornyl group and the like can be mentioned. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group and a naphthyl group, and these may be substituted with an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms.

The alkoxysilane represented by the general formula (I) in the present invention includes, for example,

Embedded image Such as tetraalkoxysilane,

Embedded image Monoorgano trialkoxy silane such as,

Embedded image And the like, and these may be used alone or in combination of two or more.

When the alkoxysilane compound represented by the general formula (I) used in the present invention is used in combination with tetraalkoxysilane, monoorganotrialkoxysilane, and diorganodialkoxysilane,
The mixing ratio is not limited, but the diorganodialkoxysilane is preferably 50 mol% or less based on the total amount of the alkoxysilane compound used in order to form a good quality and low dielectric constant silica-based coating. The amount of the alkoxysilane is preferably not more than 50 mol% based on the total amount of the alkoxysilane compound used.

The solvent (B) in the present invention includes an organic solvent. Examples of the organic solvent include alcohol solvents such as methanol, ethanol, propanol, and butanol; acetate solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and acetophenone. And glycol ether solvents such as ethylene glycol monomethyl acetate and ethylene glycol diacetate, and glycol ether solvents. These may be used alone or in combination of two or more. The amount of the solvent (B) used is such that the concentration of the polysiloxane (A) in the coating solution for forming a silica-based film is 15 to 50% by weight.
Preferably, the amount is such that

The polysiloxane (A) in the present invention must contain at least 20% by weight of a polymer having a molecular weight of 10,000 or more, preferably 30 to 50% by weight. If it is less than 20% by weight, the lowering of the dielectric constant becomes insufficient. On the other hand, if it exceeds 50% by weight, the synthesis tends to be difficult, and the handleability, film formability, and the like tend to decrease. Here, "20% by weight of a polymer having a molecular weight of 10,000 or more is used.
"Has the above" means that the polysiloxane is measured by gel permeation chromatography, the horizontal axis is the retention time, and the vertical axis is a graph drawn as the intensity due to differential refraction, and the molecular weight is 10 based on a calibration curve separately prepared using standard polystyrene. , 0
When the retention time t corresponding to 00 is calculated and the graph is divided into two by a straight line L parallel to the vertical axis passing through the retention time t, a high molecular weight region (a portion surrounded by the curve, the horizontal axis and the straight line L in the graph) for the area S ₂ of the surface area S ₁ + low molecular weight region (curve and a horizontal axis and a portion surrounded by a straight line L of the graph) [S ₁ / (S ₁
+ S ₂ )] × 100 means that the calculated value is 20 or more. The number average molecular weight of the polysiloxane (A) (measured by gel permeation chromatography and converted to standard polystyrene) is from 1,300 to 10,000.
Is preferred from the viewpoint of easy synthesis, handling, film forming property and the like.

The polysiloxane (A) of the present invention, for example, an alkoxysilane compound represented by the general formula (I) can be produced by hydrolytic condensation polymerization while removing an alcohol component which is a reaction by-product. . In this reaction, it is preferable to use an organic acid such as formic acid, maleic acid, fumaric acid and acetic acid and an inorganic acid such as hydrochloric acid, phosphoric acid, nitric acid, boric acid and sulfuric acid as a catalyst for accelerating the polymerization.
This catalyst is used in an appropriate amount according to the amount of the alkoxysilane compound as a raw material, and is used in an amount of 0.001 to 1 with respect to 1 mol of the alkoxysilane compound represented by the general formula (I).
It is preferred to be in the molar range. If the amount is too large, undesired gelation tends to be promoted. If the amount is too small, the effect of promoting the polymerization reaction tends to be insufficient.
In this reaction, a solvent can be present, and as such a solvent, an organic solvent is preferable.
Alkoxysilane compound 100 represented by general formula (I)
It is preferable to set the amount to 0 to 400 mol% with respect to the mol%.

Examples of the method for removing by-produced alcohol include heating the reactor, and flowing an inert gas to the surface of the reaction solution. The heating temperature may be a temperature at which the alcohol component evaporates, and is preferably 50 to 150 ° C. From the viewpoint of forcibly discharging the alcohol component, it is preferable to blow an inert gas onto the surface of the reaction solution. This inert gas includes nitrogen, argon,
Helium or the like is preferable, and the flow rate of the blown gas is 1
It is preferably from 00 to 500 ml / min. If the flow rate of the gas is too low, the discharge of the alcohol component is insufficient and the reaction does not proceed, and there is a risk that unreacted alkoxy groups or hydroxy groups may remain.If the flow rate of the gas is too high, the reaction proceeds rapidly and gelation occurs. There is a tendency that a silica-based coating having good film-forming properties cannot be obtained.

In the reaction, water is present in the reaction system to hydrolyze the alkoxysilane compound represented by the general formula (I). If the amount of water is too small or too large, the reaction is carried out. Since the film properties tend to deteriorate and the storage stability tends to decrease, the amount of water is preferably 50 to 100 mol% of the alkoxysilane compound represented by the general formula (I).
It is preferable that the content be in the range of 400 mol% to 400 mol%.

The polysiloxa of the hydrolysis-condensation polymerization product obtained as described above is dissolved in the above-mentioned solvent, if necessary, so that the solid content concentration becomes 1 to 50% by weight, preferably 3 to 30% by weight. And then used as a coating solution for forming a silica-based film. The thus-obtained coating solution for forming a silica-based film is applied onto a substrate such as a silicon wafer or a silicon wafer having a circuit formed thereon by a dipping method, a spin coating method, or the like. Preferably 1
Dry at 00 ° C. to 250 ° C., and then
By baking at 0 to 600 ° C., preferably 350 to 450 ° C., a silica-based coating having a thickness of about 0.1 to 2 μm can be produced.

A semiconductor device can be obtained by using this silica-based film as a wiring interlayer film (interlayer insulating film). The manufacturing process of the semiconductor device will be described below with reference to the drawings.
FIG. 1 is a manufacturing process diagram of a semiconductor device having a multilayer wiring structure. In FIG. 1, a semiconductor substrate 1 such as a silicon wafer on which a circuit is formed is covered with a protective film 2 such as a silicon oxide film except for a predetermined portion of the circuit element, and a first conductor layer 3 is formed on the exposed circuit element. Is formed. The above-mentioned silica-based coating liquid is applied onto the semiconductor substrate by a spinner method or the like, and the interlayer insulating film 4 made of a polysiloxane film is formed by removing the solvent by heat treatment and baking (step (a)).

Next, a photosensitive resin layer 5 of a chlorinated rubber type or a phenol novolak type is formed on the interlayer insulating film 4 by a spinner method, and a predetermined portion of the interlayer insulating film 4 is exposed by a known photolithography technique. The window 6A is provided so as to perform the process (step (b)).

The interlayer insulating film 4 of the window 6A is selectively etched by dry etching using a fluorine-based gas such as carbon tetrafluoride (for example, a method using a fluorine-based gas such as carbon tetrafluoride). 6B is opened. Next, the photosensitive resin layer 5 is completely removed by using an etching solution that does not corrode the first conductor layer 3 exposed from the window 6B but corrodes only the photosensitive resin layer 5 (step (c)).

Further, the second conductor layer 7 is formed by using a known metal film forming method and a photolithography technique, and the electrical connection with the first conductor layer 3 is completely performed (step (d)).

When a multilayer wiring structure having three or more layers is formed, the above steps are repeated to form each layer. That is, a step (a) of forming an interlayer insulating film to be an insulating layer on the conductor layer, a step of selectively removing a predetermined portion of the coating and opening a window (b), a predetermined portion of the lower portion of the conductor layer Steps (c) and (d) for forming the upper conductor connected to the above are repeated.

On the surface of the multilayer wiring structure thus manufactured, a surface protective layer made of an organic material such as a polyimide resin or an inorganic material such as silicon nitride is formed. A window similar to the above windows 4A and 4B may be opened in a predetermined portion of the surface protective layer in some cases. The entire semiconductor device is usually sealed with a sealing material such as an epoxy resin.

[0022]

The present invention will be described below with reference to examples. Example 1 22.7 g (0.167 mol) of methyltrimethoxysilane was dissolved in 8.0 g (0.25 mol) of methanol and cooled with ice. To this solution was added 2.98 ml of 6N hydrochloric acid and 1.04 of water.
A hydrochloric acid solution to which ml (0.057 mol) was added was added at once. After charging, the ice bath was removed and the reactor was heated to 70 ° C. Also, N ₂ gas was sprayed on the reaction solution surface at a rate of 360 ml / min in order to selectively remove by-produced methanol. The reaction was performed for 3 hours in this state. A polysiloxane resin was dissolved in isopropanol so as to have a resin concentration of 15% by weight to prepare a silica-based coating liquid. The number average molecular weight of the obtained polymer was 3,200, and the content of the component having a molecular weight of 10,000 or more was 32% by weight.

The thus obtained coating solution for forming a silica-based film is spin-coated on a silicon wafer at 2,000 rpm using a spinner, and then placed in a quartz furnace and heated in nitrogen at 30 ° C./min. Temperature from room temperature to 450 ° C,
After heating, the mixture was fired at the same temperature for 30 minutes to obtain a colorless, transparent and crack-free silica-based coating. The thickness of the film was measured and found to be 0.4 μm. An aluminum film having a thickness of 1 μm was formed on this film by a sputtering method, and the dielectric constant of the sample was measured at a frequency of 1 kHz to 100 kHz using an LF impedance meter.

Example 2 8.47 g (0.0556 mol) of tetramethoxysilane and 7.58 g (0.05%) of methyltrimethoxysilane
56 mol), 6.69 g of dimethyldimethoxysilane
(0.0556 mol) of methanol (8.0 g, 0.25
Mol) and cooled on ice. This solution was added with 6N hydrochloric acid 2.9.
A hydrochloric acid solution obtained by adding 1.00 ml (0.0556 mol) of water to 8 ml was poured at once. After charging, the ice bath was removed and the reactor was heated to 70 ° C. In order to selectively remove by-product methanol, N ₂ gas was applied to the surface of the reaction solution for 400 m.
Sprayed at a rate of 1 / min. The reaction was performed for 3 hours in this state. The produced polysiloxane resin was dissolved in propyl acetate so as to have a resin concentration of 15% by weight to prepare a silica-based coating liquid. When the molecular weight of the obtained polymer was measured, the number average molecular weight was 4,200, and the content of the component having a molecular weight of 10,000 or more was 42% by weight.

The coating solution for forming a silica-based film thus obtained is spin-coated on a silicon wafer at 2,000 rpm using a spinner, and then placed in a quartz furnace and heated in nitrogen at 30 ° C./min. Temperature from room temperature to 450 ° C,
After heating, the mixture was fired at the same temperature for 30 minutes to obtain a colorless, transparent and crack-free silica-based coating. The thickness of the film was measured and found to be 0.5 μm. An aluminum film having a thickness of 1 μm was formed on this film by a sputtering method, and the dielectric constant of the sample was measured at a frequency of 1 kHz to 100 kHz using an LF impedance meter.

Comparative Example 1 133 g (0.974 mol) of methyltrimethoxysilane
Was dissolved in 263 g of isopropanol, and a solution obtained by dissolving 2.02 g of phosphoric acid in 51.5 g (2.86 mol) of water was added dropwise to this solution over 30 minutes with stirring. After stirring for 5 hours after the completion of the dropwise addition, a polysiloxane solution was obtained. The molecular weight at this time was 1,2 as a number average molecular weight in terms of polystyrene.
The content of the component having a molecular weight of 10,000 or more was 16% by weight.

The coating solution for forming a silica-based film thus obtained is spin-coated on a silicon wafer at 2,000 rpm using a spinner, and then placed in a quartz furnace and heated in nitrogen at 30 ° C./min. Temperature from room temperature to 450 ° C,
After heating, the mixture was fired at the same temperature for 30 minutes to obtain a colorless, transparent and crack-free silica-based coating. The thickness of the film was measured and found to be 0.4 μm. An aluminum film was formed on this film to a thickness of 1 μm by a sputtering method, and the dielectric constant of the sample was measured at a frequency of 1 kHz to 100 kHz using an LF impedance meter, and was 2.8.

Comparative Example 2 29.5 g (0.194 mol) of tetramethoxysilane,
26.4 g (0.194 mol) of methyltrimethoxysilane, 23.3 g (0.19 mol) of dimethyldimethoxysilane
4 mol) was dissolved in 192 g of propyl acetate, and a solution of 0.331 g (2.85 × 10 ⁻³ mol) of maleic acid dissolved in 31.4 g (1.75 mol) of water was added to this solution. The solution was added dropwise over 30 minutes. After stirring for 5 hours after the completion of the dropwise addition, a polysiloxane solution was obtained. The molecular weight at this time was 900 in terms of polystyrene as a number average molecular weight, and the content of the component having a molecular weight of 10,000 or more was 2% by weight.

The thus obtained coating solution for forming a silica-based film is spin-coated on a silicon wafer at 2,000 rpm using a spinner, and then placed in a quartz furnace and heated in nitrogen at 30 ° C./min. Temperature from room temperature to 450 ° C,
After heating, the mixture was fired at the same temperature for 30 minutes to obtain a colorless, transparent and crack-free silica-based coating. The thickness of the film was measured and found to be 0.2 μm. An aluminum film was formed on this film to a thickness of 1 μm by a sputtering method, and the dielectric constant of the sample was measured at a frequency of 1 kHz to 100 kHz using an LF impedance meter, and was 2.8.

[0030]

The coating liquid for forming a silica-based coating according to the first aspect is capable of producing a silica-based coating having good film-forming properties and a low dielectric constant. According to the method for producing a silica-based coating according to the second aspect, a silica-based coating having good film formability and a low dielectric constant can be easily produced with high yield. The silica-based coating according to the third aspect has good uniformity and a low dielectric constant. The semiconductor device according to the fourth aspect is highly reliable having a silica-based coating having good film uniformity and a low dielectric constant.

[Brief description of the drawings]

FIG. 1 is a process chart showing an example of a manufacturing process of a semiconductor device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Protective film 3 First conductor layer 4 Interlayer insulating film 5 Photosensitive resin layer 6A, 6B Window 7 Second conductor layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigeru Nobe 4-3-1-1, Higashicho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Chemical Co., Ltd.Yamazaki Plant (72) Inventor Yoshibe Abe 1411− 6 F term (reference) 4G072 AA25 FF09 GG02 HH30 MM01 QQ09 RR05 UU01 4J038 DL031 JA19 JA33 JA56 JA57 KA06 MA14 NA01 NA17 NA24 PA19 PB09 5F033 QQ11 QQ37 RR06 RR22 RR23 RR25 SS22 XX24 BA02 BC02

Claims (4)

[Claims] (A) General formula (I) (Wherein R ¹ is an alkyl group having 1 to 6 carbon atoms or 6 carbon atoms)
Represents an aryl group of 10 to 10, a plurality of R ¹ may be the same or different, R ² represents an alkyl group having 1 to 10 carbon atoms, and a plurality of R ² may be the same or different , N is an integer of 0 to 2) represented by the following formula:
A coating solution for forming a silica-based film, comprising a polysiloxane containing 20% by weight or more of a polymer of 000 or more and (B) a solvent. 2. A silica-based coating obtained by applying the coating solution for forming a silica-based coating according to claim 1 on a substrate, drying at 50 to 350 ° C., and then heating and curing at 200 to 600 ° C. in a nitrogen atmosphere. Manufacturing method. 3. A silica-based coating obtained by the method according to claim 2. 4. A semiconductor device having the silica-based coating according to claim 3.