JP2002212502A - Composition for forming film, method for forming porous film, and porous film - Google Patents

Abstract

(A) A (A) containing 30 to 100 mol% of a structural unit (T unit) represented by the following general formula (1): R ¹ —SiZ ₃ (1), and the T unit Among them, a structural unit containing one silanol group represented by the following general formula (2) R ¹ —Si (OH) Z ′ ₂ (2) (T-
2 units) in an amount of 30 to 80 mol% (provided that R
¹ represents a substituted or unsubstituted monovalent hydrocarbon group, and Z is OH
Groups, hydrolyzable groups and siloxane residues, at least one of which represents a siloxane residue and Z 'represents a siloxane residue. ), A film-forming composition comprising: a silanol group-containing silicone resin having a number average molecular weight of 100 or more; and (B) a compound having a polyalkylene oxide structure. EFFECTS By using the composition of the present invention, the composition is flat and uniform while being porous and having a low dielectric constant.
It is possible to form an optimum film as an interlayer insulating film when used for manufacturing a semiconductor device having a small dielectric constant and a large mechanical strength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film-forming composition capable of forming a porous film excellent in dielectric properties, adhesion, uniformity of coating film and mechanical strength, a method for forming a porous film, and a method for forming the same. It relates to the formed porous membrane.

[0002]

2. Description of the Related Art With the progress of high integration of semiconductor integrated circuits, an increase in wiring delay time due to an increase in wiring capacitance, which is a parasitic capacitance between metal wirings, has been increasing. Hinders the high performance of The wiring delay time is a so-called RC delay which is proportional to the product of the resistance of the metal wiring and the capacitance between the wirings.

Therefore, in order to reduce the wiring delay time, it is necessary to reduce the resistance of the metal wiring or reduce the capacitance between the wirings.

[0004] By lowering the capacitance between wirings, even if the semiconductor device is more highly integrated, wiring delay is not caused. Therefore, it is possible to increase the speed and to reduce the power consumption.

As a method of reducing the capacitance between wirings, it is conceivable to lower the relative dielectric constant of an interlayer insulating film formed between metal wirings. A porous film has been studied in place of the oxide film. As a practical film that can achieve a relative dielectric constant of 2.0 or less, a porous film can be said to be almost the only film, and various methods for forming a porous film have been proposed.

As a first method for forming a porous film, a precursor solution of a siloxane polymer containing a thermally unstable organic component is synthesized, and the precursor solution is applied on a substrate to form a coating film. There is a method in which a large number of pores are formed after the volatile component by decomposing and volatilizing the organic component by performing heat treatment after the formation.

As a second method for forming a porous material, a wet gel is formed by applying a silica sol solution on a substrate or performing a CVD method, and then controlling the evaporation rate of a solvent from the wet gel. A method of forming a porous material by performing a condensation reaction of silica sol while suppressing volume shrinkage is known.

As a third method for forming a porous film, a solution of fine silica particles is applied on a substrate to form a coating film, and then the coating film is baked and hardened to form a large number of fine particles between the fine silica particles. Methods for forming holes are known.

As a fourth method, Japanese Patent Laid-Open No. 2000-4
No. 4875 discloses that (A) R ¹ _n Si (OR ² ) _4-n (R
¹ is a monovalent organic group, wherein n is an integer of 0 to 2), (B) a metal chelate compound, and (C) a compound having a polyalkylene oxide structure. There has been proposed a composition for forming a porous film.

[0010] However, each of these methods has significant disadvantages. That is, the first porous forming method is as follows:
It is necessary to synthesize a precursor solution of a siloxane polymer, so that there is a problem that the cost is high.In addition, since the precursor solution is applied to form a coating film, the amount of silanol groups remaining in the coating film increases. Therefore, there are problems such as a degassing phenomenon in which moisture and the like evaporate in a heat treatment step performed later and deterioration of film quality due to moisture absorption of the porous film.

In addition, the second method for forming a porous film requires a special coating device to control the evaporation rate of the solvent from the wet gel, so that there is a problem that the cost is increased and the method is fine. A large number of silanols remain on the surface of the pores, and as they are, they have high hygroscopicity and cause significant deterioration of the film quality. Therefore, it is necessary to silylize the silanol on the surface, which causes a problem that the process becomes complicated. In addition, when the wet gel is formed by the CVD method, a special CVD device different from a plasma CVD device usually used in a semiconductor process is required, so that the cost is also increased.

In the third method for forming a porous film, the diameter of the pores formed between the silica fine particles is determined by the deposited structure of the silica fine particles deposited geometrically. Since the diameter becomes very large, there is a problem that it is difficult to reduce the relative dielectric constant of the porous film to 2 or less.

In the case of the fourth method, (A), (B),
The metal chelate compound of the component (B) in the three components of (C)
It is a necessary component for improving the compatibility of the components (A) and (C) and making the thickness of the coating film after curing uniform, which is essential, but complicates the components and complicates the production process. This is also a factor that increases costs, which is not preferable. That is, there is a demand for the development of a material that can form a uniform solution without a chelate component and that has a flat coating film after curing.

The present invention solves the above problems at once,
It is an object of the present invention to provide a film-forming composition, a method for forming a porous film, and a porous film capable of forming a porous film having a relative dielectric constant of 2.0 or less in a simple process and at low cost.

[0015]

Means for Solving the Problems and Embodiments of the Invention From the conventional studies, the present inventors have found that a silicone component usually has low compatibility with a compound having a polyalkylene oxide structure, and is mixed uniformly as it is. Had the knowledge that it was difficult. However, this problem involves controlling the structure of the silicone component, specifically, containing 30 to 100 mol% of a structural unit (T unit) represented by the following general formula (1) R ¹ —SiZ ₃ (1). And a structural unit containing one silanol group represented by the following general formula (2) R ¹ —Si (OH) Z ′ ₂ (2) (T-
2 units) in an amount of 30 to 80 mol% (provided that R
¹ represents a substituted or unsubstituted monovalent hydrocarbon group, and Z is OH
Groups, hydrolyzable groups and siloxane residues, at least one of which represents a siloxane residue and Z 'represents a siloxane residue. ), A silanol group-containing silicone resin having a number average molecular weight of 100 or more can be used. By using such a silicone resin, a uniform solution is obtained, and even after the solution is applied and cured, the solution is uniform. It has been found that a coating can be formed.

When a mixture of such a silicone resin and a compound having a polyalkylene oxide structure is applied and cured, a uniform and flat film can be formed. When heated at a temperature at which the compound component having the above is decomposed, the curing of the silicone resin component proceeds, and at the same time, the compound component having a polyalkylene oxide structure is decomposed, and the decomposition products are evaporated, and voids are formed in the film, and eventually the porous material As a result of measuring the relative dielectric constant of such a film, the film showed a value much smaller than the intrinsic dielectric constant of the silicone resin, and the content of the compound component having a polyalkylene oxide structure Film having an arbitrary dielectric constant of about 1.2 to 2.7 by adjusting different compositions of It found that can be formed, and completed the present invention.

Accordingly, the present invention provides a film-forming composition comprising (A) the above silicone resin and (B) a compound having a polyalkylene oxide structure.
This composition is applied to a substrate, and the formed film is heated at a temperature equal to or higher than the decomposition temperature of the component (B), and a porous film obtained by the method is provided. provide.

Hereinafter, the present invention will be described in detail. The silicone resin component (A) used in the present invention is defined as follows.

The structural unit (T unit) represented by the following general formula (1) R ¹ —SiZ ₃ (1) is 30 to 100 mol%,
Preferably, the structural unit contains 60 to 100 mol% and contains ^one silanol group represented by the following general formula (2) R ¹ —Si (OH) Z ′ ₂ (2) among the T units ( T-
2 units) in an amount of 30 to 80 mol%, preferably 40 to 70 mol% (wherein R ¹ represents a substituted or unsubstituted monovalent hydrocarbon group, Z represents an OH group, a hydrolyzable group) And at least one is a siloxane residue.) And a silanol group-containing silicone resin having a number average molecular weight of 100 or more.

Here, in the structural unit constituting the silicone resin represented by the following general formula (1) R ¹ —SiZ ₃ (1), R
^As the monovalent hydrocarbon group, one having 1 to 12 carbon atoms is preferable, and an alkyl group, an aryl group, an aralkyl group, an alkenyl group or the like, or a part or all of these hydrogen atoms is a halogen atom such as a fluorine atom. And groups substituted with an epoxy-containing group such as a glycidyl group or a glycidyloxy group. Specific examples include an alkyl group, an aryl group, and a glycidyl group. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group, and preferably have 1 to 5 carbon atoms. May be linear or branched, and a hydrogen atom may be substituted with a fluorine atom. Examples of the aryl group include a phenyl group and a naphthyl group.

Further, Z represents an OH group, a hydrolyzable group or a siloxane residue. Specific examples of the hydrolyzable group include:
Alkoxy groups such as methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, sec-butoxy group, t-butoxy group, vinyloxy group, 2-propenoxy group, etc., acyloxy groups such as phenoxy group, acetoxy group and the like. Groups, oxime groups such as butanoxime groups, and amino groups. Among these, an alkoxy group is preferable, and particularly, a methoxy group, an ethoxy group, an isopropoxy group, and a butoxy group are preferably used because of easy control during hydrolysis and condensation. Further, a siloxane residue means a substituent bonded to an adjacent silicon atom via an oxygen atom to form a siloxane bond;
Although-(Si≡), it can be expressed as O _1/2 because an oxygen atom is shared with an adjacent silicon atom.

Further, in the silicone resin, a structural unit (T-) having one silanol group represented by the following general formula (2) R ¹ —Si (OH) Z ′ ₂ (2)
2 units) in an amount of 30 to 80 mol%. put it here,
R ¹ is defined as above, and Z ′ is a siloxane residue.

[0023] Incidentally, the silicone resin, as a group other than R ¹ -SiZ ₃ in the formula ^(1), R 1 ₃ -SiZ
(M _{^{units), R 1 2 -SiZ 2 (}} D units), may include SiZ ₄ a (Q units). In this case, the M unit is 0 to 30 mol%, particularly 0 to 10 mol%, the D unit is 0 to 50 mol%, particularly 0 to 20 mol%, and the Q unit is 0 to 30 mol%, particularly 0 to 0 mol%.
The content can be 10 mol%. However, at least one of Z of the M unit, D unit, and Q unit is a siloxane residue.

Next, the molecular weight of the silanol group-containing silicone resin used in the present invention will be described.
When trying to form a uniform film, it is desirable that the silicone resin has a certain molecular weight or more in order to form a uniform film. From this point, in the present invention, it is necessary to use a silicone resin having a number average molecular weight of 100 or more. If it is less than 100, it is difficult to form a uniform film because an appropriate structure cannot be secured, and storage stability is also poor. Preferably, the number average molecular weight is between 500 and 10,000
0, particularly preferably from 1,000 to 5,000.

It is preferable that the silicone resin applicable to the present invention satisfies the above conditions and, at the same time, contains a certain amount or more of a silanol group.
It is preferred that the content be at least 10% by weight, especially 6 to 20% by weight. If the content of the silanol group is too small, the absolute amount of the silanol group contributing to crosslinking becomes insufficient, so that the hardness of the cured film may decrease.

As long as the above conditions are satisfied, the silicone resin may be produced by any method. A specific manufacturing method will be described below.

As a raw material for the production, a silane compound having a functional group such as an alkoxy group, an alkenyloxy group, an acyloxy group, a halogen atom, an amino group or an oxime group as a hydrolyzable group, or a partial hydrolysis / condensation thereof Things can be used. From the viewpoint of easy control of the hydrolysis reaction or easy treatment of the hydrolysis by-product, and from an economic viewpoint, as the hydrolyzable group, it is preferable to employ an alkoxy group or a chloro atom, particularly an alkoxy group. Good. When a chloro atom is used, it is preferable to completely hydrolyze the chloro atom so as not to leave a chlorine atom in the silicone resin. In addition, the number of hydrolyzable groups,
Containing one, two, three or four per silicon atom,
Any silane compound having an organic substituent R ¹ that satisfies the above conditions can be used. However, when the number of hydrolyzable groups X is 3, that is, the hydrolyzable silane compound represented by R ¹ SiX ₃ 30 to 10 in the hydrolyzable silane compound
0 mol%, especially 50-100 mol%, is used. In addition,
Other hydrolyzable silane compounds, SiX _4, R ¹ ₂
It can be used SiX _2, R ¹ ₃ SiX.

Specifically, tetrafunctional silanes (four hydrolyzable groups) such as tetrachlorosilane, tetramethoxysilane, tetraethoxysilane and tetrabutoxysilane: Si
X ₄ , methyltrichlorosilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltributoxysilane, methyltriisopropenoxysilane, ethyltrichlorosilane, ethyltrimethoxysilane, propyltrichlorosilane,
Butyltrichlorosilane, butyltrimethoxysilane,
Trifunctional silanes (three hydrolyzable groups) such as hexyltrichlorosilane, hexyltrimethoxysilane, decyltrichlorosilane, decyltrimethoxysilane, phenyltrichlorosilane, phenyltrimethoxysilane, cyclohexyltrichlorosilane, and cyclohexyltrimethoxysilane: R ¹ SiX ₃ , dimethyldichlorosilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldiisopropoxysilane, dimethyldibutoxysilane, dimethyldiisopropenoxysilane, propylmethyldichlorosilane, propylmethyldimethoxysilane, hexylmethyldisilane Chlorosilane, hexylmethyldimethoxysilane, phenylmethyldichlorosilane, phenylmethyldimethoxysilane, diphenyldichlorosilane, diphenyldichlorosilane Difunctional silanes such as Tokishishiran (two hydrolyzable groups): R ¹ ₂ SiX _2, trimethylchlorosilane, trimethyl methoxy silane, trimethyl ethoxy silane, trimethyl isopropenoxysilane silane, monofunctional silanes such as dimethylphenyl chlorosilane (hydrolysis one decomposable group): R ¹ ₃ SiX, and so-called silane coupling agent having an organic functional group, such as vinyl trichlorosilane, vinyl trimethoxysilane, vinyltriethoxysilane, 5-hexenyltrimethoxysilane, 3-glycidol Xypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 4-vinylphenyltrimethoxysilane, 3- (4-bi Butylphenyl) propyl trimethoxysilane, 4-vinylphenyl methyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-
(2-aminoethyl) aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-
Mercaptopropyltriethoxysilane, vinylmethyldichlorosilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3- (meth) acrylic Roxypropylmethyldimethoxysilane, 3- (meth) acryloxypropylmethyldiethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldi Ethoxysilanes and their partial hydrolysates are examples of silane compounds that can be used.

From the viewpoint of operability and easy removal of by-products, it is more preferable to use alkoxysilane, especially methoxysilane or ethoxysilane. The usable organosilicon compound is not limited to the above. Further, one or a mixture of two or more of these silane compounds may be used.

The most characteristic feature of the silanol group-containing silicone resin according to the present invention is that it is obtained by hydrolyzing the hydrolyzable silane compound in an aqueous solution. When the hydrolysis is carried out under hydrophilic conditions containing substantially no organic solvent, a unique silicone resin having a structure containing a large amount of T-2 units, which characterizes the present invention, is obtained. This silicone resin is prepared through the following steps.

First, the first stage is a process of hydrolyzing and condensing the above-mentioned various hydrolyzable organic silane compounds in an aqueous solution having a pH of 1 to 7. The amount of water used for hydrolysis is
It is preferable to use 50 to 5000 parts by weight based on 100 parts by weight of the silane compound or the mixture thereof which is blended to have a composition satisfying the above conditions. When the amount is less than 50 parts by weight, the amount of water in the reaction system is small, so that it is difficult to control the reactivity of the silanol group described above, and it may not be possible to impart structure. If it exceeds 5000 parts by weight, the silane concentration of the raw material may be too low, and the condensation reaction may be slowed down.

The hydrolysis is carried out by adding a silane compound to an aqueous solution and stirring. A hydrolysis catalyst may be added to promote the hydrolysis, particularly the initial hydrolysis. The hydrolysis catalyst may be added to the aqueous solution before adding the silane compound, or may be added to the dispersion after dispersing the silane compound. As the hydrolysis catalyst, conventionally known catalysts can be used, and those in which the added aqueous solution exhibits acidity of pH 1 to 7 are preferably used. Particularly preferred are acidic hydrogen halides, carboxylic acids, sulfonic acids, acidic or weakly acidic inorganic salts, and solid acids such as ion exchange resins. Specific examples include hydrofluoric acid, hydrochloric acid, nitric acid, inorganic acids such as sulfuric acid, acetic acid, maleic acid,
Examples include organic acids represented by trifluoroacetic acid, sulfonic acids such as methanesulfonic acid, paratoluenesulfonic acid, and trifluoromethanesulfonic acid, and cation exchange resins having a sulfonic acid group or a carboxylic acid group on the surface.

When a hydrolysis catalyst is used, the amount of the catalyst added is 0.00 to 1 mol of the hydrolyzable group on the silicon atom.
It is preferably in the range of 1 to 10 mol%. Under a strongly acidic condition of less than pH 1 or an alkaline condition of more than pH 7, the silanol group tends to be extremely unstable.
More preferably, the pH of the aqueous solution used is 2-6. Since the amount of water is in a large excess with respect to the amount of the hydrolyzable group, the hydrolysis proceeds completely. By stirring at room temperature or under heating under these conditions, condensation between silanol groups easily proceeds.

At this stage, since a hydrolysis by-product is present in the system, the silane reaction mixture, which is a precursor of the silanol group-containing silicone resin, is dissolved in the solution.

The second step is a step of removing hydrolysis by-products from the solution containing the reaction mixture outside the system to obtain a system mainly containing a silanol group-containing silicone resin and water.

That is, the solution containing the silane reaction mixture obtained in the first step is heated under normal pressure at a temperature of 80 ° C. or lower, preferably about 30 to 70 ° C., or at room temperature to 80 ° C. 20 m, preferably at room temperature to 70 ° C
By reducing the pressure to from mHg to normal pressure, hydrolysis by-products such as alcohol are distilled off, and the system is substantially converted to a system comprising a silanol group-containing silicone resin and water. In this process, the condensation degree of the silicone resin further advances.

The silicone resin which has been hydrolyzed and condensed to some extent in the first stage becomes polymerized with further progress of condensation and gradually loses hydrophilicity. At the same time, most of the external environment in which the silicone resin is dissolved becomes water.

The hydrolysis by-product is produced in an amount of 30 to
By removing 100%, the silanol group-containing silicone resin can no longer be dissolved in the solution, and the solution becomes slightly turbid or turbid. 50-100% of by-product
Is removed, the silicone resin becomes insoluble in the aqueous layer,
Settle by standing.

The silicone resin separated from the aqueous layer in this manner can be taken out itself, but it is also possible to add an organic solvent that is not uniformly compatible with water and separate it from the aqueous layer as a solution. It is. Such organic solvents include diethyl ether, diisopropyl ether, methyl isobutyl ketone, ethyl acetate, n-butyl acetate,
Isobutyl acetate, benzene, toluene, xylene and the like.

The silicone resin used in the present invention can be produced in this manner, but any method can be used as long as it is in the range defined above. It is not something to be done.

Next, the compound having a polyalkylene oxide structure as the component (B) will be described.

The compound having a polyalkylene oxide structure in the present invention includes polyethylene oxide, polypropylene oxide or a compound obtained by copolymerizing both. The terminal is not particularly limited, and those having a hydroxyl group, an alkyl group, or an acyl group are generally known. As the alkyl group, a methyl group, an ethyl group,
Examples include a propyl group, a butyl group and a 2-ethylhexyl group, and examples of the acyl group include an acetoxy group and a propionyloxy group.

As the compound having a polyoxyalkylene oxide structure, polyether silicone can also be used. This is a general term for compounds having a structure in which a silicone chain is bonded to the end of a polyalkylene oxide structure, and is a material widely used industrially as a leveling agent for paint and a foam stabilizer for urethane foaming.

Examples of the polyether silicone compound include one-terminal modified polyether silicone having a polyalkylene oxide chain bonded to one end of a silicone chain, and polyether silicone modified at both ends having a polyalkylene oxide chain bonded to both ends of a silicone chain. And a side chain-modified polyether silicone in which a polyalkylene oxide chain is bonded to the main chain portion of the silicone chain, and any of these can be used.

When the silicone resin according to the present invention is used, these compounds having a polyalkylene oxide structure usually have higher solubility than a resin having a small proportion of silicon atoms bonded to silanol groups. Show. Therefore, a uniform film can be formed.

In the present invention, the compound having a polyalkylene oxide structure has a number average molecular weight in terms of polystyrene of preferably 100 to 100,000, particularly preferably 1 to 100,000.
000 to 20,000. The mixing ratio of the component (A) and the component (B) is preferably 5:95 to 95: 5 by weight,
Particularly preferably, the ratio is 10:90 to 80:20.

In order to further increase the compatibility of these two components, it is effective to add an alkoxysilane having an epoxy group-containing substituent. Examples of such alkoxysilanes are γ-glycidoxypropyltrimethoxysilane, (γ-glycidoxypropyl) triethoxysilane, (γ-glycidoxypropyl) methyldimethoxysilane, (γ-glycidoxypropyl) Propyl) methyldiethoxysilane, (γ-glycidoxypropyl) dimethylmethoxysilane, (β-3,4-epoxycyclohexylpropyl) trimethoxysilane,
(Β-3,4-epoxycyclohexylpropyl) methyldimethoxysilane, (β-3,4-epoxycyclohexylpropyl) triethoxysilane, (β-3,4-
Examples thereof include epoxycyclohexylpropyl) methyldiethoxysilane, which are added in an amount of 0.5 to 10% by weight, particularly 1 to 7% by weight, based on the total amount of the components (A) and (B). Is preferred.

The film-forming composition of the present invention comprises the above (A)
(B) component is contained, in this case, these (A),
The component (B) is used after being dissolved in a solvent. Examples of such a solvent include the above-mentioned organic solvents that make the silicone resin soluble. This solvent is used in an amount of 100 to 1000 parts by weight, especially 150 to 50 parts by weight, per 100 parts by weight of the silicone resin.
It is preferred that the proportion be 0 parts by weight.

To form a film using the film-forming composition of the present invention, first, the composition of the present invention is applied to a substrate to form a coating film. Here, examples of the substrate on which the composition of the present invention can be applied include semiconductors, glass, ceramics, and metals, and any application method can be used as long as it is a method commonly used in semiconductor device manufacturing. Examples thereof include spin coating, dipping, and roller blades. Here, the thickness of the coating film to be formed is typically 0.2 to 20 μm in the case of an interlayer insulating film.
It is. Next, the formed coating film is heated. The purpose of this method is to evaporate the solvent in the coating solution and fix the shape of the coating film in a step usually called prebaking. The heating temperature at this time is a temperature sufficient to evaporate the solvent in the coating solution.

By heating the film thus formed to a temperature sufficient for curing the component (A) and decomposing and evaporating the component (B), a cured film having pores can be formed. it can.

As the heating method, 300 to 500 ° C.
It is preferable to heat at a temperature of the present composition, whereby a porous film having pores in the case of the present composition is obtained. Heating time is 1 minute ~
It is about 2 hours, more preferably 5 minutes to 1 hour. If the heating temperature is too low, curing of component (A) and (B)
The decomposition and evaporation of the components do not proceed, the film is insufficiently cured, and only a film having a small mechanical strength can be formed. A temperature that is too high results in excessive decomposition of the component (A), which also results in a decrease in the film strength, and a semiconductor device. It may not be compatible with the manufacturing process, and a temperature of 350 to 450C is more preferable.

When the heating is performed in the air or in an inert gas atmosphere, the distribution of the pores and the mechanical strength of the film are different. By controlling this, the film is controlled. Physical properties can be controlled, and any material can be used without limitation.

Examples of the inert gas include a nitrogen gas and an argon gas. In the present invention, the inert gas is preferably used so that the oxygen concentration becomes, for example, a value of 5 ppm or less. By heating in the inert gas in this manner, the influence of oxygen is eliminated, and the film obtained is obtained. Can have a lower dielectric constant.

Further, in the method for producing a film of the present invention, by heating (reacting) the composition for forming a porous film under reduced pressure, the influence of oxygen is eliminated and the dielectric constant of the obtained film is lowered. It can be a value.

The film obtained by heating the composition of the present invention by the method of the present invention usually has pores of 100 nm or less, and has a porosity of 5 to 70%. The dielectric constant of the film is usually 2.7 to 1.2, preferably 2.5 to 1.2, and more preferably 2.2 to 1.2. Therefore, the film of the present invention is suitable as an insulating film, and is particularly suitable as an interlayer insulating film for highly integrated circuits.

[0056]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Production Examples, Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Production Example 1] A 2-liter flask was charged with 408 g (3.0 mol) of methyltrimethoxysilane, and 800 g of water was added at 0 ° C under a nitrogen atmosphere, followed by thorough mixing. Here, under ice cooling, 0.05N hydrochloric acid aqueous solution 216
g was added dropwise over 40 minutes to carry out a hydrolysis reaction. After the completion of the dropwise addition, the mixture was stirred at 10 ° C. or lower for 1 hour, and further stirred at room temperature for 3 hours to complete the hydrolysis reaction.

Next, methanol and water produced by the hydrolysis were distilled off under reduced pressure at 70 ° C. × 60 Torr for 1 hour to obtain 1136 g of a solution. The solution was cloudy and separated into two layers when allowed to stand for 24 hours. The silicone resin insoluble in water settled out.

To this cloudy solution was added methyl isobutyl ketone 2
After adding 00 g and stirring well, the mixture was allowed to stand and separated from the aqueous layer. This gave 398 g of solution.

The silanol group-containing silicone resin ²⁹
NMR analysis revealed that T units were 100 mol%, of which T-1 units were 2 mol% and T-2 units were 42 mol%.
The silicone resin contained 56 mol% of T-3 units and 56 mol% of T-3 units, and the number average molecular weight of this silicone resin was 1,800. However, T-1 _{Unit: CH 3 Si (OH) 2} Z 'T-2 _{units: CH 3 Si (OH) Z} ' 2 T-3 units: CH ₃ SiZ _'3

[Production Example 2] A reaction was carried out in the same manner as in Production Example 1 except that 367 g of methyltrimethoxysilane and 41 g of dimethyldimethoxysilane were charged into a 2 liter flask.
2 g were obtained. The number average molecular weight in terms of polystyrene by GPC was 2,100. The obtained silicone resin has 89 mol% of T units and 11 mol% of D units,
4 mol% of T-1 units and 40 of T-2 units among T units.
Mol% and T-3 units were 56 mol% (in addition, T-
1 to T-3 units are the same as above).

[Examples and Comparative Examples] A film obtained by spin-coating a coating film solution having the components shown in Table 1 was heat-treated to obtain a porous film, which was evaluated. The coating solution is obtained by dissolving the components (A) and (B) in propylene glycol monomethyl ether acetate to form a solution having a non-volatile residue of 30 to 40% by weight.
Spin-coated. The rotation speed at this time is 1500 to 300
Zero rotation was performed for 60 seconds. After the application, prebaking was performed at 100 ° C. for 60 seconds, and thereafter, the film was heated in the air at 400 ° C. for 60 minutes in an oven. The dielectric constant of the coating film was measured at a frequency of 100 kHz using an HP16451B electrode manufactured by Yokogawa Hewlett-Packard Co., Ltd. and an HP4284A Precision LCR meter. Table 1 shows the results.

[0063]

[Table 1] (Note) Flatness: good, bad

[0064]

Embedded image

[0065]

By using the composition of the present invention,
Porous, low dielectric constant, flat and uniform, low dielectric constant, and high mechanical strength, making it possible to form an optimal film as an interlayer insulating film when used in semiconductor device manufacturing. Become.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Akira Yamamoto 1-10 Hitomi, Matsuida-cho, Usui-gun, Gunma Prefecture F-term in the Silicon Electronics Research Laboratory, Shin-Etsu Chemical Co., Ltd. 4J038 DF012 DL051 DL071 DL132 GA03 GA15 NA11 NA12 NA17 NA24 PA19 PB09 PC02 5F033 RR21 RR23 RR29 SS22 XX23 5F058 AA10 AC03 AF04 AG01 AH02

Claims (4)

[Claims] (A) containing 30 to 100 mol% of a structural unit (T unit) represented by the following general formula (1) R ¹ —SiZ ₃ (1), and Structural unit containing one silanol group represented by the formula (2) R ¹ —Si (OH) Z ′ ₂ (2) (T-
2 units) in an amount of 30 to 80 mol% (provided that R
¹ represents a substituted or unsubstituted monovalent hydrocarbon group, and Z is OH
Groups, hydrolyzable groups and siloxane residues, at least one of which represents a siloxane residue and Z 'represents a siloxane residue. ), A film-forming composition comprising: a silanol group-containing silicone resin having a number average molecular weight of 100 or more; and (B) a compound having a polyalkylene oxide structure. 2. The composition according to claim 1, wherein the compound having a polyalkylene oxide structure as the component (B) is polyether silicone. 3. A method for forming a porous film, comprising applying the composition according to claim 1 or 2 to a substrate, and heating the formed film at a temperature not lower than the decomposition temperature of the component (B). 4. A porous membrane obtained by the method according to claim 3.