JPH0143773B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ladder-shaped lower alkyl polysilsesquioxane suitable for use as an insulating protective film (passive film) or interlayer insulating film for integrated circuits, which has the ability to form a heat-resistant thin film. More specifically, the present invention relates to a ladder-like lower alkylpolysilsesquioxane containing a specific amount of a relatively low molecular weight ladder-like lower alkylpolysilsesquioxane.

Organopolysiloxanes with a ratio of oxygen atoms to silicon atoms of 1.5 are generally called polysilsesquioxanes, and in particular, ladder-like lower alkyl polysilsesquioxanes are silicone resins with excellent heat resistance. . For this reason,
Recently, research has been carried out on the use of this ladder-like lower alkyl polysilsesquioxane as an insulating protective film for integrated circuits or as an interlayer insulating film. The resins used in these applications are
The conventionally known ladder-shaped lower alkyl organopolysil Sesquioxane has a drawback in that it has poor crack resistance, that is, cracks occur when a thin film is formed on a substrate and heated at high temperatures, and it has been desired to solve this problem.

In order to solve the above problem, the present inventors
As a result of extensive research, we have developed a ladder-shaped lower alkyl polysilsesquioxane with a specific molecular weight distribution, that is, a ladder-shaped lower alkyl polysilsesquioxane containing a specific amount of relatively low molecular weight ladder-shaped lower alkyl polysilsesquioxane. Oxane is
It was discovered that it has excellent crack resistance, and the present invention was achieved.

That is, the present invention provides the formula [In the formula, R and R' are the same or different lower alkyl groups, and n represents the average degree of polymerization. ] In the ladder-shaped lower alkyl polysilsesquioxane represented by Provided is a ladder-shaped lower alkylpolysilsesquioxane having the ability to form a heat-resistant thin film, characterized in that it is dominated by a portion with a converted molecular weight of 20,000 or less.

In the ladder-like lower alkyl polysilsesquioxane of the present invention, R and R' are lower alkyl groups such as methyl group, ethyl group, n-propyl group, etc., and R and R' may be the same or different. You can leave it on. A preferred ladder-like lower alkyl polysilsesquioxane is a ladder-like methylpolysilsesquioxane in which R and R' are methyl groups, and in this case, it has particularly excellent heat resistance, and is a ladder-like methylpolysilsesquioxane before heat curing. When sesquioxane is fired in air by gradually increasing the temperature from room temperature to 700℃,
The weight residual rate reaches 80-90%, and the
Products that have been heat-cured at 450°C for 2 hours do not lose weight even when heated to 730°C in nitrogen.
Furthermore, when fired at 800°C in nitrogen, the weight retention rate reaches 95-96%. In addition, n indicates the average degree of polymerization, and a weight average molecular weight of 40,000 to 500,000 in terms of standard polystyrene determined by GPC is preferable from the viewpoint of heat resistance and handleability.
50000-300000 is preferred.

In addition, if the portion with a standard polystyrene equivalent molecular weight of 20,000 determined by GPC is less than 15% (weight), cracks will occur when heated at high temperatures. If the following parts exceed 30% (by weight), cracks will occur when heated at high temperatures, storage stability will be poor, and gelation will occur easily.

The ladder-like lower alkylpolysilsesquioxane of the present invention, for example, the ladder-like methylpolysilsesquioxane, can be produced by the method proposed in Japanese Patent Application No. 116493/1980, but in some cases, the product may be , it is necessary to subject it to a treatment to adjust the molecular weight distribution. According to the method disclosed in Japanese Patent Application No. 55-116493, ladder-like methylpolysilsesquioxane is produced as follows. That is, by dissolving CH ₃ SiCl ₃ in either ketone or ether and adding water to the resulting ketone or ether solution under stirring,
By hydrolyzing CH ₃ SiCl ₃ , then condensing the hydrolyzate, and subjecting the obtained condensate to a treatment to adjust the molecular weight distribution, if necessary, the desired ladder-like methyl polysilsesque Oxane is produced.

In this manufacturing method, CH ₃ SiCl ₃ is dissolved in either a ketone or an ether. The ketone or ether used is not particularly limited, and examples of the ketone include methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone,
As the ether, ethylene glycol dimethyl ether, di-normal propyl ether, dioxane, diethylene glycol, dimethyl ether, etc. can be used. These ketones and ethers should not be used in combination with each other, but two or more types of ketones or two or more types of ethers may be used. Furthermore, when a mixture of ketone and ether is used, the average molecular weight of the resulting ladder-like methylpolysilsesquioxane is considerably lower than when either ketone or ether is used, and the average molecular weight is much lower than the standard determined by GPC. The weight average molecular weight in terms of polystyrene is
It is often less than 20,000. Also, heptane,
Aliphatic hydrocarbons such as octane; toluene,
Aromatic hydrocarbons such as xylene; 1,2-dichloroethane, 1,1,2-trichloroethane,
Halogenated hydrocarbons such as 1,3-dichloropropane, chlorobenzene, etc.; Aliphatic alcohols such as n-propyl alcohol, n-butyl alcohol, isobutyl alcohol, etc.; ethyl propionate, ethyl isobutyrate, isobutyl acetate, etc. Fatty acid alkyl esters and the like may be mixed with ketones or ethers. When these solvents are used in combination with ketones or ethers, preferably the ketone or ether is 50%
(capacity) or more.

The amount of ketone or ether used is not particularly limited, but is preferably 5-20 per part by volume of CH ₃ SiCl ₃
This is the capacity part. Furthermore, even when a ketone or ether is mixed with another solvent, the same amount is used in terms of the ketone or ether in the mixed solvent.

When adding water to a CH ₃ SiCl ₃ solution under stirring, it is preferable to gradually add water from the viewpoint of ease of controlling the reaction. Water usage is preferably
It is about 3-30 mol per 1 mol of CH ₃ SiCl ₃ .

After adding water, the reaction mixture is heated in an oil bath or the like. The heating temperature may be any temperature below 130°C, but low temperatures require long heating. Generally speaking, at a temperature of 100-120℃
- It is preferable to heat for about 6 hours. Note that during the heating operation, the contents may be stirred or the solvent may simply be left to reflux.

When CH ₃ SiCl ₃ is hydrolyzed and further condensed,
When an amine is present, the reaction proceeds smoothly even at a high concentration of CH ₃ SiCl ₃ and a ladder-like lower alkyl polysilsesquioxane with a high molecular weight is obtained. As the amine, various primary, secondary, or tertiary amines such as triethylamine, tri-n-propylamine, triisopropylamine, diethylamine, ethylamine, pyridine, and ethylenediamine are used. Particularly preferred is triethylamine or diethylamine. The amine can be added to the solution of CH ₃ SiCl ₃ before adding water to the solution, or it can be added to the solvent before dissolving the CH ₃ SiCl ₃ in the ketone or ether. The amount of amine used is not particularly limited, but preferably
The amount is up to about 3 moles per mole of CH ₃ SiCl ₃ , more preferably about 0.3-2 moles.

When adding an amine, water is added dropwise to the CH ₃ SiCl ₃ solution, and a white precipitate of amine hydrochloride gradually forms. If water is added dropwise, the white precipitate will dissolve. After the addition of water is complete, the reaction mixture is heated as if no amine was added.

After the reaction is complete, whether or not an amine is added, the solvent layer is washed with water, and this washing is repeated until the water after washing becomes neutral. In order to prevent gelation of lusesquioxane, the solvent layer can be dried with a desiccant such as anhydrous sodium sulfate to obtain a ladder-like methylpolysilsesquioxane solution, and if necessary, the solvent can be removed. , a ladder-like methylpolysilsesquioxane is obtained.

The molecular weight distribution of the ladder-shaped lower alkyl polysilsesquioxane obtained by the above method is inappropriate, and the portion with a standard polystyrene equivalent molecular weight of 20,000 or less determined by GPC is reduced by 15-30%.
(by weight), if the proportion is not included, the separation method,
The molecular weight distribution is adjusted by a preparative gel permeation chromatography method or a blending method so that the content of the above-mentioned low molecular weight ladder-like lower alkyl polysilsesquioxane is 15-30% (by weight). Ru. According to the fractionation method, a solution of the obtained ladder-shaped lower alkyl polysilsesquioxane is mixed with a solvent that does not dissolve the ladder-shaped lower alkyl polysilsesquioxane, such as acetonitrile, and the ladder-shaped lower alkyl polysilsesquioxane is dissolved. The sesquioxane is reprecipitated to obtain a ladder-like lower alkyl polysilsesquioxane having the desired molecular weight distribution. In this case, it is necessary to appropriately select the concentration of the solution of the ladder-shaped lower alkyl polysilsesquioxane, the type of solvent that does not dissolve the ladder-shaped lower alkyl polysilsesquioxane, and the amount of these solvents used. According to the preparative gel permeation chromatography method, the obtained ladder-like lower alkyl polysilsesquioxane solution is
A ladder-shaped lower alkyl polysilsesquioxane solution with the desired molecular weight distribution is recovered by subjecting it to GPC to remove fractions containing unnecessary molecular weight portions, and if necessary, the solvent is removed to obtain the desired ladder-shaped solution. A lower alkyl polysilsesquioxane is obtained. According to the blending method, two or more solutions of ladder-shaped lower alkyl polysilsesquioxanes having different molecular weight distributions are mixed, the solvent is removed as necessary, and ladder-shaped lower alkyl polysilsesquioxanes having the desired molecular weight distribution are mixed. An alkylpolysilsesquioxane is obtained.

The ladder-shaped lower alkyl polysilsesquioxane having a specific molecular weight distribution of the present invention can be formed into a thin film by dissolving it in an appropriate solvent, applying the resulting solution onto a substrate, and drying it. can. Application methods include, for example, spray application,
Commonly used methods can be used, such as spinner coating. The thin film obtained by this method can be dried even after the solvent has evaporated before heat curing, or after heat curing, or after curing at 400-500°C.
No cracks occur even after heat treatment at .degree. C., and it can be widely used as a heat-resistant insulating protective film or interlayer insulating film, especially as an electronic material used in integrated circuit manufacturing.

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples.

Note that GPC measurements in Examples and Comparative Examples were performed under the following conditions.

GPC measurement conditions Equipment: High-temperature high-speed gel permeation chromatogram (Model 150-C ALC/GPC) manufactured by Waters, USA Column: SHODEX A-8M manufactured by Showa Denko K.K., length
50cm Measurement temperature: 40℃ Flow rate: 1 c.c./min Under the above conditions, using tetrahydrofuran as a solvent, dissolve 1 g of ladder-like lower alkyl polysilsesquioxane in 100 c.c. of tetrahydrofuran and prepare the sample. did. Further, as the standard polystyrene, standard polystyrene manufactured by Plessyer Chemical Company, USA was used.

Example 1 Methyl isobutyl ketone (1200 ml) was added to a reaction vessel equipped with a reflux condenser, a dropping funnel, and a stirring bar.
and to this are added CH ₃ SiCl ₃ (140 ml) and triethylamine (80 ml). Cool the reaction vessel on ice,
While stirring, slowly add water (200 ml) dropwise.
A white precipitate of triethylamine hydrochloride gradually forms, but by still adding water, the white precipitate is dissolved. After dropping the water, place it on the oil bath.
The reaction mixture is heated to reflux for 5 hours at an oil bath temperature of 100°C. After the reaction is completed, the solvent layer is washed until the washing water becomes neutral, and then dried using anhydrous sodium sulfate as a drying agent. Next, remove the desiccant and
The solvent is distilled off under reduced pressure to obtain a ladder-like methylpolysilsesquioxane. This ladder-like methylpolysilsesquioxane is vacuum-dried at 40° C. overnight, and then the molecular weight distribution is measured by GPC to obtain curve a of the GPC chart shown in the attached drawing.
From this curve, the standard polystyrene equivalent molecular weight
It can be seen that it contains a portion with a low molecular weight of 20,000 or less at a ratio of 27% (by weight) and that the weight average molecular weight in terms of standard polystyrene is 110,000.

2.5 g of the ladder-like methylpolysilsesquioxane thus obtained is dissolved in 10 ml of toluene, and this is applied onto a silicon wafer using a spinner at 1500 rpm. Thereafter, the coated material is heated at 80° C. for 1 hour to remove the solvent, and then heated and cured at 350° C. for 1 hour to form a thin film. This thin film
Heat treatment at 450°C for 30 minutes, then leave at room temperature.
No cracks occur in this case either. The thickness of the thin film is 2 μm.

Comparative Example 1 The methyl isobutyl ketone solution of ladder-like methylpolysilsesquioxane obtained in Example 1 after removing the desiccant was concentrated (liquid volume 300 ml) to a concentration of 28% (by weight), and this concentrate was 4 into acetonitrile to precipitate a ladder-like methylpolysilsesquioxane. The ladder-like methylpolysilsesquioxane thus obtained was vacuum dried at 40° C. overnight, and then the molecular weight distribution was measured by GPC to obtain curve b of the GPC chart shown in the attached drawing. This curve shows that it contains a low molecular weight portion of 20,000 or less in terms of standard polystyrene at a ratio of 14% (by weight), and that the weight average molecular weight in terms of standard polystyrene is 161,000. That is, the proportion of low molecular weight moieties is lower than that of Example 1.

2.5 g of the ladder-like methylpolysilsesquioxane thus obtained is dissolved in 10 ml of toluene. The obtained solution is applied onto a silicon wafer using a spinner at 1500 rpm. The obtained coating was heated at 80°C for 1 hour in the same manner as in Example 1, and then
Heat cure at 350℃ for 1 hour, then heat cure at 450℃ for 30 minutes.
After a minute of heat treatment, cracks occur in the thin film. The thickness of the thin film is 2 μm.

Example 2 A methyl isobutyl ketone solution of ladder-like methylpolysilsesquioxane after removing the desiccant obtained by the method of Example 1 was prepared with a concentration of 60% (weight) (liquid volume 150%).
ml) and pour the concentrate into 450 ml of acetonitrile to precipitate a ladder of methylpolysilsesquioxane. The ladder-like methylpolysilsesquioxane thus obtained was vacuum dried at 40° C. overnight, and the molecular weight distribution was then measured by GPC to obtain curve C of the GPC chart shown in the attached drawing. From this curve, the low molecular weight part with a standard polystyrene equivalent molecular weight of 20,000 or less
It can be seen that the content is 20% (by weight) and that the weight average molecular weight in terms of standard polystyrene is 136,000.

2.5 g of the ladder-shaped methylpolysilsesquioxane thus obtained was dissolved in 10 ml of toluene, and the resulting solution was placed on a silicone wafer.
Apply with spinner at 2000 rpm. The obtained coated material was heated at 80°C for 1 hour in the same manner as in Example 1, then heated and cured at 350°C for 1 hour, and then heated at 450°C for 30 hours.
No cracks occur even after heat treatment for several minutes. The thickness of the thin film is 1.8 μm.

Comparative Example 2 8 g of ladder-like methylpolysilsesquioxane obtained in Example 1 was dissolved in 33 ml of toluene,
While maintaining the resulting solution at 25°C, add 56 ml of acetonitrile to it and stir well. Once the precipitate has formed, the precipitate and the supernatant are separated by centrifugation at 15,000 rpm for 40 minutes. Furthermore, while keeping the obtained supernatant at 25°C, add 8 mL of acetonitrile to it.
ml, stir well, and when a precipitate forms,
Centrifuge again for 40 minutes at 15,000 rpm.
Next, the solvent of the supernatant liquid is distilled off under reduced pressure, and the residue is vacuum-dried at 40°C overnight. The molecular weight distribution of the ladder-like methylpolysilsesquioxane thus obtained was measured by GPC to obtain curve d of the GPC chart shown in the attached drawing. This curve shows that it contains a low molecular weight portion of 20,000 or less in terms of standard polystyrene equivalents at a ratio of 39% (by weight), and that the weight average molecular weight in terms of standard polystyrene equivalents is 33,000. That is, the proportion of low molecular weight moieties is higher than that in Example 1.

This ladder-like methylpolysilsesquioxane
Dissolve 2.5g in 10ml of toluene and use the resulting solution.
Apply spinner onto silicon wafer at 2000 rpm. When the coated material was heated at 80°C for 1 hour in the same manner as in Example 1, further heat-cured at 350°C for 1 hour, and then heat-treated at 450°C for 30 minutes, cracks appeared in the thin film. The thickness of the thin film is 1.7 μm.

Comparative Example 3 Methyl isobutyl ketone (260
ml) and tetrahydrofuran (90ml),
Add to this methyltrichlorosilane (47ml, 0.4mol)
and triethylamine (56ml, 0.4mol) were added.

The reaction vessel was ice-cooled and water was slowly added dropwise while stirring. A white precipitate of triethylamine hydrochloride gradually formed, but the white precipitate was dissolved again by further addition of water. The amount of water added was about 50 to 100 ml.

Next, use an oil bath at an oil bath temperature of 100° to 110°C.
The mixture was heated to reflux for an hour.

After the reaction was completed, the organic layer was separated, washed with water until the washing water became neutral, and dried over anhydrous sodium sulfate. Thereafter, the desiccant was removed, the mixture was concentrated to a point where the polymer precipitated, and the mixture was poured into methanol to precipitate the polymer.

The obtained precipitate was thoroughly washed with methanol and dried under vacuum. The weight average molecular weight of the ladder-like methylpolysilsesquioxane thus obtained was 63,800 in terms of standard polystyrene.

In addition, the proportion of a low molecular weight portion having a standard polystyrene equivalent molecular weight of 20,000 or less was 45 wt%.

This ladder-like methylpolysilsesquioxane
A 22% by weight toluene solution was applied onto a silicon wafer using a spinner. When the obtained coating was heated at 80° C. for 1 hour in the same manner as in Example 1, further heat-cured at 350° C. for 1 hour, and then heat-treated at 450° C. for 30 minutes, cracks occurred in the thin film. The thickness of the thin film is
It was 2 μm.

Comparative Example 4 Methyltrichlorosilane (11.7 ml,
0.1 mol) and triethylamine (14 ml, 0.1 mol) were dissolved in a mixed solvent of methyl isobutyl ketone (45 ml) and tetrahydrofuran (45 ml),
Hydrolysis was carried out in the same manner as in Comparative Example 3.

After the reaction was completed, the organic layer was separated, washed with water until the washing water became neutral, and dried over anhydrous sodium sulfate. Thereafter, the desiccant was removed, the mixture was concentrated to a point where the polymer precipitated, and the mixture was poured into methanol to precipitate the polymer.

The obtained precipitate was thoroughly washed with methanol and dried under vacuum. The weight average molecular weight of the ladder-like methylpolysilsesquioxane thus obtained was 619,300 in terms of standard polystyrene.

Furthermore, the proportion of low molecular weight portions having a standard polystyrene equivalent molecular weight of 20,000 or less was 77 wt%.

A 22% by weight toluene solution of the ladder-shaped methylpolysilsesquioxane thus obtained was applied onto a silicon wafer using a spinner. The obtained coating was heated at 80°C for 1 hour in the same manner as in Example 1,
Further heat curing at 350℃ for 1 hour, then continue to heat cure at 450℃.
When heat treated at ℃ for 30 minutes, cracks appeared in the thin film. The thickness of the thin film was 2 μm.

Comparative Example 5 3 g of the ladder-like methylpolysilsesquioxane obtained in Comparative Example 1 was dissolved in 20 ml of diethylene glycol dimethyl ether according to the method described in Example 3 of JP-A-53-88099, and 3.8 g of trimethylamine hydrochloride was added thereto. 5 ml of water was added and the mixture was stirred at 130°C for 4 hours.

After the reaction was completed, the reaction product was poured into methanol to obtain a white precipitate. This was thoroughly washed with methanol and then vacuum dried.

The weight average molecular weight of the ladder polymethylsilsesquioxane thus obtained was 147,200 in terms of standard polystyrene.

In addition, the proportion of a low molecular weight portion having a standard polystyrene equivalent molecular weight of 20,000 or less was 48 wt%.

This ladder-like methylpolysilsesquioxane
A 22% by weight toluene solution was applied onto a silicon wafer using a spinner. When the obtained coating was heated at 80° C. for 1 hour in the same manner as in Example 1, further heat-cured at 350° C. for 1 hour, and then heat-treated at 450° C. for 30 minutes, cracks occurred in the thin film. The thickness of the thin film is
It was 2 μm.

Comparative Example 6 Comparative Example 3 was added to a mixed solvent of methyl isobutyl ketone (15 ml) and tetrahydrofuran (6 ml) according to the method described in Example 4 of JP-A-53-88099.
Ladder-shaped methylpolysilsesquioxane 3 obtained in
Dissolve g and add 0.1 g of triethylamine hydrochloride to this.
Methanol (5 ml) containing 20% was added, and the mixture was stirred at 90°C for 4 hours.

After the reaction was completed, the reaction solution was poured into methanol to obtain a white precipitate. This was thoroughly washed with methanol and dried in vacuum.

The weight average molecular weight of the ladder-like methylpolysilsesquioxane thus obtained was 78,100 in terms of standard polystyrene. In addition, the proportion of low molecular weight parts with a standard polystyrene equivalent molecular weight of 20,000 or less is 33wt.
It was %.

22 of this ladder-like methylpolysilsesoxane
A wt% toluene solution was applied onto a silicon wafer using a spinner. When the obtained coating was heated at 80° C. for 1 hour in the same manner as in Example 1, further heat-cured at 350° C. for 1 hour, and then heat-treated at 450° C. for 30 minutes, cracks occurred in the thin film. The thickness of the thin film is
It was 2 μm.

Comparative Example 7 Polysiloxane 3 with a molecular weight of 9000 obtained in Comparative Example 3 was added to diethylene glycol dimethyl ether according to the method described in Example 5 of JP-A-53-88099.
Dissolve g and add 5.5 g of triethylamine hydrochloride to this.
Water (7 ml) containing 20% was added, and the mixture was stirred at 90°C for 4 hours.

The reaction solution was poured into methanol to obtain a white precipitate.
This was washed with methanol and vacuum dried.

The weight average molecular weight of the ladder-like methylpolysilsesquioxane thus obtained was 136,600 in terms of standard polystyrene.

Furthermore, the proportion of low molecular weight portions having a standard polystyrene equivalent molecular weight of 20,000 or less was 33 wt%.

This ladder-like methylpolysilsesquioxane
A 22wt% toluene solution was applied onto a silicon wafer using a spinner. When the obtained coating was heated at 80° C. for 1 hour in the same manner as in Example 1, further heat-cured at 350° C. for 1 hour, and then heat-treated at 450° C. for 30 minutes, cracks occurred in the thin film. The thickness of the thin film is
It was 2 μm.

[Brief explanation of drawings]

The drawing shows a GPC chart, the vertical axis shows the concentration of a ladder-like methylpolysilsesquioxane solution separated by GPC, and the horizontal axis shows the molecular weight in terms of standard polystyrene.

Claims (1)

[Claims] 1 formula [In the formula, R and R' are the same or different lower alkyl groups, and n represents the average degree of polymerization. In the ladder-like lower alkyl polysilsesquioxane represented by ], 15-30% (by weight) of it has a standard polystyrene equivalent molecular weight of 20,000 or less as determined by gel permeation chromatography. A ladder-like lower alkyl polysilsesquioxane having the ability to form a heat-resistant thin film, characterized in that it is dominated by