JP2003165952A - Coating composition for producing insulating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prepare a porous silica film which has a low relative permittivity and the mechanical strengths to sufficiently withstand a chemical and mechanical polishing (CMP) step in the copper wiring step of a semiconductor device and, simultaneously, reduces the amount of gaseous pollutants on forming a via hole. <P>SOLUTION: The coating composition for producing an insulating film comprises a silica precursor containing a specified ratio of the silicon atom derived from a trifunctional alkoxysilane to the silicon atom derived from a tetrafunctional alkoxysilane, a block copolymer, an acid catalyst, and a solvent. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a coating composition capable of providing an insulating thin film having a sufficiently low relative permittivity of a thin film, an extremely high mechanical strength and a sufficient CMP (chemical mechanical polishing) resistance. Regarding things.

[0002]

2. Description of the Related Art Porous silica is widely used as a structural material, a catalyst carrier, an optical material and the like because it has excellent properties such as light weight and heat resistance. For example, in recent years, expectations have been gathered from the viewpoint that porous silica can lower the dielectric constant.

Conventionally, a dense silica film has been generally used as a material for an interlayer insulating film for a multilayer wiring structure of a semiconductor element such as an LSI. However, in recent years, the wiring density of LSIs has been miniaturized, and the distance between adjacent wirings on the substrate has been narrowed accordingly. At this time, if the dielectric constant of the insulator is high, the capacitance between the wirings increases, and as a result, the delay of the electric signal transmitted through the wiring becomes significant, which is a problem. In order to solve such a problem, a material having a lower dielectric constant is strongly required as a material for an insulating film for a multilayer wiring structure. On the other hand, as a wiring material, instead of conventional aluminum,
The use of lower resistance copper is another reason for the demand for materials with lower dielectric constants.

Japanese Patent Laid-Open No. 5-85762 and International Publication (WO) 99/03926 pamphlet show that a mixture system of a general alkoxysilane and an organic polymer has a very low dielectric constant, uniform pores and pore distribution. There is disclosed a method for obtaining porous silica having a porosity. Further, JP-A-4-285081 discloses a method for carrying out a sol-gel reaction of alkoxysilane in the presence of a specific organic polymer to obtain porous silica having a uniform pore size. Furthermore, JP-A-2001-491
In Japanese Patent Publication No. 77, the amount of the bifunctional and / or trifunctional alkoxysilane charged is controlled to be larger than the amount of the tetrafunctional alkoxysilane charged, and a block copolymer is used as the organic polymer to improve the dielectric property. A method of forming a low density film having excellent rate characteristics and water absorption and having a small void size is disclosed.

However, no porous silica having a sufficiently low relative permittivity, stable with time, and sufficient mechanical strength and adhesion to withstand the CMP process has been obtained by any of the methods. There is a situation. In the present invention, the CMP step is a step of flattening the surface of excess copper on the interlayer insulating film by polishing the surface of the copper when wiring copper is embedded in a groove in the interlayer insulating film formed by etching. That is. In this process, compressive stress and shear stress are applied not only to the interlayer insulating film, but also to the barrier thin film on the thin film (usually depositing hundreds to thousands of Å silicon oxide on the interlayer insulating film). Therefore, the interlayer insulating film is required to have mechanical strength and adhesion. Further, generally, when the organic polymer is to be removed from the composite of these silica and the organic polymer by heating, a heating temperature of 450 ° C. or higher is a major constraint on the semiconductor element manufacturing process.

For example, in consideration of oxidation and crystal growth of metal wiring, thermal stress, etc. in the semiconductor element manufacturing process, the upper limit of the heating temperature is around 400 ° C. and a non-oxidizing atmosphere is recommended. However, under these heating conditions,
In the above-mentioned silica-organic polymer composite, most of the organic polymer remains or becomes char, for example, when creating a multilayer wiring structure, the gas derived from the organic polymer remaining in the lower layer is generated from the lower layer and the upper layer. May cause a decrease in adhesion and peeling. In order to solve this, a means of using an organic polymer which is easily thermally decomposed has been investigated, but the organic polymer is too sensitive to heat and is extremely dangerous to handle, or the sol-gel reaction catalyst causes a decrease in molecular weight. There is a problem that the film quality deteriorates and the film formability deteriorates, and because the compatibility with the silica precursor is poor, precipitation occurs in the coating solution, decomposition during film formation and volatilization to densify the film. It was difficult to make porous silica.

[0007]

SUMMARY OF THE INVENTION The present invention is intended to solve the above problems, in which a porous insulating silica thin film has a low relative permittivity, is stable, and has high mechanical strength. It is intended to provide a coating composition for producing a porous insulating silica thin film, which has an adhesive force sufficient to withstand a CMP step in a copper wiring step.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, trifunctional alkoxysilane and its hydrolyzate contained in a coating composition for producing an insulating thin film, A silica precursor in which the number of moles of silicon atoms derived from a polycondensate is controlled to be less than 50 mole% of the number of moles of silicon atoms derived from a polycondensate, a tetrafunctional alkoxysilane and a hydrolyzate thereof. The present invention has been completed by finding that a coating composition for producing an insulating thin film containing a specific organic polymer and a specific solvent solves the above problems.

The above and other objects, characteristics and benefits of the present invention will be apparent from the detailed description and claims below. That is, the present invention is: (A) At least one or more of alkoxysilane represented by the following general formula (1) and its hydrolyzate and polycondensate, and alkoxysilane represented by the following general formula (2) and its hydrolysis Which is a silica precursor containing at least one or more of a polycondensate and an alkoxysilane represented by the general formula (1), a hydrolyzate thereof, and a silicon atom derived from a polycondensate The mole fraction of silicon atoms derived from the general formula (2) is 1 to 50 mol% with respect to the total of silicon atoms derived from the alkoxysilane represented by the formula (2) and its hydrolyzate and polycondensate.
Si (OR ¹ ) ₄ ... (1) R ² (Si) (OR ¹ ) ₃ ... (2) (wherein R ¹ and R ² may be the same or different) And each independently represents a monovalent organic group.) (B) An organic polymer containing a linear or branched binary or more block copolymer, and (C) an alcohol solvent, a ketone solvent, or an amide solvent. And at least one solvent selected from the group of ester solvents, and a coating composition for producing an insulating thin film,

2. The organic polymer described in 1 above is an end-capped organic compound in which at least one linear or branched block copolymer of two or more elements and at least one of the end groups are chemically inactive to the silica precursor. 2. A coating composition for producing an insulating thin film according to 1, which contains a polymer. 3. The coating composition for producing an insulating thin film according to the above 1 or 2, wherein the organic polymer includes at least 1% by weight or more of the block copolymer. 4. The coating composition for producing an insulating thin film according to any one of 1 to 3 above, wherein the coating composition for producing an insulating thin film contains at least one kind of acid. After applying the coating composition for producing an insulating thin film according to any one of 1 to 4 above, a silica precursor is gelated to obtain a silica / organic polymer composite thin film, and the silica / organic polymer composite is subsequently obtained. 5. A porous insulating silica thin film obtained by removing an organic polymer from a body thin film; 6. A wiring structure characterized by using the insulating silica thin film described in 5 above. The present invention relates to a semiconductor device including the wiring structure described in 6 above.

The porous silica referred to in the present invention is characterized in that it is a porous silica whose main component is represented by the following general formula (4). R _x SiO _y (4) (R represents a linear, branched or cyclic alkyl group having 1 to 8 carbon atoms or an aryl group, and 0 ≦ x <2, 1 <y ≦ 2). Further, in the alkoxysilane represented by the general formula (1) described above in the present invention, Si (O
R ¹ ) ₄ is called a tetrafunctional alkoxysilane, and R ² (Si) (OR ¹ ) ₃ in the general formula (2) is a trifunctional alkoxysilane. The alkoxysilane is hydrolyzed and polycondensed, and the condensation rate thereof is about 90% or more is referred to as silica in the present invention.

The coating composition for producing an insulating thin film (hereinafter referred to as coating composition) used in the present invention will be described below. The coating composition used in the present invention is mainly composed of a silica precursor (A) containing any one or more of alkoxysilane and its hydrolyzate and polycondensate, an organic polymer (B) and a solvent (C). And First, the silica precursor (A) used in the present invention will be described. The silica precursor used in the present invention is any one or more of tetrafunctional alkoxysilane and its hydrolyzate and polycondensate, and any one of trifunctional alkoxysilane and its hydrolyzate and polycondensate. Or at least one of them is contained in a specific ratio.

First, of the tetrafunctional alkoxysilane represented by the general formula (1) and the trifunctional alkoxysilane represented by the general formula (2), which can be used in the silica precursor (A) of the present invention. A specific example will be described below. The tetrafunctional alkoxysilane is specifically tetramethoxysilane, tetraethoxysilane, tetra (n-propoxy) silane, tetra (i-propoxy) silane, tetra (n-butoxy) silane, tetra (sec-butoxy).
Examples thereof include silane and tetra (tert-butoxy) silane.

Specific examples of trifunctional alkoxysilanes among the alkoxysilanes represented by the general formula (2) include trimethoxysilane, triethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, and ethyltriethoxysilane. Methoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, isobutyltriethoxysilane, cyclohexyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, vinyltrimethoxysilane,
Vinyltriethoxysilane, allyltrimethoxysilane,

Allyltriethoxysilane, methyltri-
n-propoxysilane, methyltri-iso-propoxysilane, methyltri-n-butoxysilane, methyltri-sec-butoxysilane, methyltri-tert-
Butoxysilane, ethyltri-n-propoxysilane,
Ethyltri-iso-propoxysilane, ethyltri-
n-butoxysilane, ethyltri-sec-butoxysilane, ethyltri-tert-butoxysilane, n-propyltri-n-propoxysilane, n-propyltri-iso-propoxysilane, n-propyltri-n-
Butoxysilane, n-propyltri-sec-butoxysilane, n-propyltri-tert-butoxysilane, i-propyltrimethoxysilane, i-propyltriethoxysilane, i-propyltri-n-propoxysilane, i-propyl Tri-iso-propoxysilane, i-propyltri-n-butoxysilane,

I-propyltri-sec-butoxysilane, i-propyltri-tert-butoxysilane, n
-Butyltrimethoxysilane, n-butyltriethoxysilane, n-butyltri-n-propoxysilane, n-
Butyltri-iso-propoxysilane, n-butyltri-n-butoxysilane, n-butyltri-sec-butoxysilane, n-butyltri-tert-butoxysilane, n-butyltriphenoxysilane, sec-butyltrimethoxysilane, sec- Butyl-tri-n-propoxysilane, sec-butyl-tri-iso-propoxysilane, sec-butyl-tri-n-butoxysilane, sec-butyl-tri-sec-butoxysilane, sec-butyl-tri-tert- Butoxysilane,

T-butyltrimethoxysilane, t-butyltriethoxysilane, t-butyltri-n-propoxysilane, t-butyltri-iso-propoxysilane, t-butyltri-n-butoxysilane, t-butyltri-sec- Butoxysilane, t-butyl tri-te
rt-butoxysilane, phenyltri-n-propoxysilane, phenyltri-iso-propoxysilane, phenyltri-n-butoxysilane, phenyltri-se
Examples thereof include c-butoxysilane and phenyltri-tert-butoxysilane. A partial hydrolyzate of an alkoxysilane may be used as a raw material. Among these tetrafunctional and trifunctional alkoxysilanes, tetramethoxysilane, tetraethoxysilane, trimethoxysilane, triethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane and dimethyldiethoxy are particularly preferable. It is silane.

The silica precursor of the present invention contains at least one or more of the above alkoxysilanes and their hydrolyzed and polycondensed products. The hydrolyzate also includes a partial hydrolyzate. For example, in the case of the tetrafunctional alkoxysilane used as the silica precursor (A), it is not necessary that all four alkoxys be hydrolyzed, and for example, 1
Only one may be hydrolyzed, two or more may be hydrolyzed, or a mixture thereof may be present. Further, the polycondensate contained in the silica precursor (A) in the present invention means the silica precursor (A)
The silanol groups of the hydrolyzate of Si are condensed to form Si-O-Si.
Although a bond is formed, it is not necessary that all of the silanol groups are condensed, and a mixture of some of the silanol groups and a mixture of those having different degrees of condensation are shown.

The silica precursor of the present invention has the general formula (1)
A tetrafunctional alkoxysilane represented by the formula, a hydrolyzate thereof and a polycondensate-derived silicon atom, and a trifunctional alkoxysilane represented by the general formula (2), a hydrolyzate and a polycondensate thereof. With respect to the total of the silicon atoms derived from
The number of silicon atoms derived from the trifunctional alkoxysilane represented by the general formula (2) and its hydrolyzate and polycondensate is 1
It is characterized in that it is at least mol% and less than 50 mol% (hereinafter, alkoxysilane and its hydrolyzate and polycondensate are referred to as alkoxysilane and the like). 5 mol% or more and less than 50 mol%, more preferably 20 mol% or more 5
It is less than 0 mol%. When the trifunctional alkoxysilane or the like is in this range, the siloxane bond concentration in the porous silica thin film becomes sufficient and high mechanical strength is exhibited. 1 mol% of silicon atoms derived from trifunctional alkoxysilane etc.
If it is less than 50%, the relative dielectric constant of the thin film will not decrease, and if it exceeds 50 mol%, the mechanical strength of the thin film will decrease, which is not preferable.

In the present invention, a monofunctional or difunctional alkoxysilane can be used instead of the trifunctional alkoxysilane. However, from the viewpoint of mechanical strength of the thin film, the trifunctional alkoxysilane is used. It is particularly preferable to use. In the present invention, by controlling the number of moles of trifunctional silicon atoms in the silica precursor as described above, and by combining with a specific organic polymer described later and further with an acid, the water absorption is low and the relative dielectric constant is An excellent porous silica thin film having a significantly low modulus, a high modulus and a high adhesion can be obtained. The content of the silica precursor in the coating composition of the present invention can be expressed as the total solid content concentration. As will be described later, the total solid content concentration is 2 depending on the thickness of the target insulating thin film.
-30% by weight is preferable, and the storage stability is also excellent.

Next, the organic polymer (B) in the present invention will be described. Of the organic polymers that can be used in the present invention, the block copolymer will be described first. This organic polymer has a low thermal decomposition temperature when the coating film is converted into a porous silica thin film by heating and baking as described below. , And a linear or branched binary or more block copolymer having a moderately good compatibility with a silica precursor and silica, wherein the block portion is a linear or cyclic oxyalkylene group having 1 to 8 carbon atoms. Is an organic polymer having a repeating unit of 60% by weight or more in one polymer chain.

Here, the reason that the compatibility is reasonably good is that
The block copolymer used in the present invention has good affinity with the silica precursor and silica. A moderately good affinity between them controls the phase separation state between the silica precursor and the polymer, and is extremely extreme when the block copolymer is extracted from silica in the subsequent step to form a porous body. Since there are no pores having large or small pore diameters and the pore diameters are uniform, the surface smoothness of the obtained thin film is further improved and the mechanical strength is also high.

Specific block copolymers include binary block copolymers such as polyethylene glycol / polypropylene glycol, polyethylene glycol / polybutylene glycol, polyethylene glycol / polypropylene glycol / polyethylene glycol, polypropylene glycol / polyethylene glycol / polypropylene glycol, Examples thereof include polyether block copolymers such as linear ternary block copolymers such as polyethylene glycol / polybutylene glycol / polyethylene glycol.

Further, as the branched block copolymer, at least three of the hydroxyl groups contained in the sugar chain represented by glycerol, erythritol, pentaerythritol, pentitol, pentose, hexitol, hexose, heptose and the like and a polymer chain are provided. Examples thereof include a structure in which at least three of the bonded structure and / or the hydroxyl group and the carboxyl group contained in the hydroxyl acid are bonded to the block copolymer chain. Specifically, glycerol, polyethylene glycol, polypropylene glycol, erythritol, polyethylene glycol, polypropylene glycol, polyethylene glycol and the like are included.

Specific examples of sugar chains that can be used other than the sugar chains used to obtain the above block copolymer on branch include sorbitol, mannitol,
Xylitol, threitol, maltitol, arabitol, lactitol, adonitol, cellobitol, glucose, fructose, sucrose, lactose, mannose, galactose, erythrose, xylulose, allulose, ribose, sorbose, xylose,
Examples include arabinose, isomaltose, dextrose, glucoheptose and the like. Specific examples of the hydroxyl acid include citric acid, malic acid, tartaric acid,
Examples thereof include gluconic acid, glucuronic acid, glucoheptonic acid, glucooctanoic acid, threonic acid, saccharic acid, galactonic acid, galactaric acid, galacturonic acid, glyceric acid, and hydroxysuccinic acid.

Further, in the present invention, a block copolymer obtained by addition-polymerizing an alkylene oxide with an aliphatic higher alcohol can also be used. Specifically, polyoxyethylene lauryl ether, polyoxypropylene lauryl ether, polyoxyethylene oleyl ether, polyoxypropylene oleyl ether, polyoxyethylene cetyl ether, polyoxypropylene cetyl ether, polyoxyethylene stearyl ether, polyoxypropylene Stearyl ether etc. are mentioned. The terminal group of the block copolymer is not particularly limited, but includes a hydroxyl group, a linear and cyclic alkyl ether group, an alkyl ester group, an alkylamide group,
It is preferably a group modified with an alkyl carbonate group, a urethane group or a trialkylsilyl group.

One of the effects of the present invention is that the amount of the block copolymer in the coating composition of the present invention is 1% by weight or more based on the total amount of the polymers including the organic polymers other than the block copolymers described below. The hygroscopicity of the porous silica thin film is remarkably suppressed, and an extremely low dielectric constant is achieved. If it is less than 1% by weight, the effect of the present invention is not exhibited. A more preferable content is 5% by weight or more. More preferably, it is 10% by weight or more. In the present invention, the polymer main chain structure disappears by heating and is easily converted to porous silicon oxide, aliphatic polyether, aliphatic polyester, aliphatic polycarbonate, aliphatic polyanhydride as a main constituent component It is also preferable to use an organic polymer in which at least one of the polymer end groups has a group that is chemically inert to the silica precursor.

The polymer having at least one of the polymer end groups which can be used in the present invention has a group chemically inactive to the silica precursor will be described below. Suitable polymer end groups include linear, branched and cyclic alkyl ether groups having 1 to 8 carbon atoms, alkyl ester groups and alkyl amide groups, and alkyl carbonate groups. The above polymers may be used alone or as a mixture of plural polymers. Further, the main chain of the polymer may include a polymer chain having any repeating unit other than the above, as long as the effect of the present invention is not impaired.

Further, since the end group of the present invention has particularly good compatibility with the silica precursor, the branched polymer is preferable as the polymer form because it can have more end groups in the molecule. In such a case, the branched portion is at least three of the hydroxyl groups contained in the sugar chain represented by glycerol, erythritol, erythrose, pentaerythritol, pentitol, pentose, hexitol, hexose, and heptose as described above. It is preferable that the organic polymer chain is bonded to the organic polymer chain and / or the organic polymer chain is bonded to at least three hydroxyl groups and carboxyl groups contained in the hydroxyl acid.

Examples of the aliphatic polyether of the present invention have a main chain of polyethylene glycol, polypropylene glycol, polyisobutylene glycol, polytrimethylene glycol, polytetramethylene glycol, polypentamethylene glycol, polyhexamethylene glycol, polydioxolane. Examples thereof include alkylene glycols such as polydioxepane whose at least one terminal is alkyl ether, alkyl ester, alkyl amide, or alkyl carbonate. The group of ether, ester, amide, and carbonate may be directly chemically bonded to the repeating unit at the polymer terminal, or may be bonded via an organic group.

Examples of the etherified end groups of the aliphatic polyether include those in which at least one end of the above alkylene glycols is etherified with, for example, methyl ether, ethyl ether, propyl ether, glycidyl ether, and the like. Specifically, for example, polyethylene glycol monomethyl ether, polyethylene glycol dimethyl ether, polypropylene glycol dimethyl ether, polyisobutylene glycol dimethyl ether, polyethylene glycol diethyl ether, polyethylene glycol monoethyl ether, polyethylene glycol dibutyl ether, polyethylene glycol monobutyl ether, polyethylene glycol diglycidyl ether. , Polyethylene polypropylene glycol dimethyl ether Ether, glycerin polyethylene glycol trimethyl ether, pentaerythritol polyethylene grayed reel tetramethyl ether, pentitol polyethylene glycol pentamethyl ether, sorbitol polyethylene glycol hexamethyl ether is particularly preferably used.

As the aliphatic polyethers having an ester group at the terminal, at least one terminal of the above alkylene glycols is, for example, acetic acid ester, propionic acid ester, acrylic acid ester, methacrylic acid ester,
Examples include benzoic acid esters. Also,
It is also preferable to use an alkylene glycol in which the terminal is converted to carboxymethyl ether and the terminal carboxyl group is converted to alkyl ester. Specifically, for example,
Polyethylene glycol monoacetate, polyethylene glycol diacetate, polypropylene glycol monoacetate, polypropylene glycol diacetate, polyethylene glycol dibenzoate, polyethylene glycol diacrylate, polyethylene glycol monomethacrylate, polyethylene glycol dimethacrylate Ester, polyethylene glycol biscarboxymethyl ether dimethyl ester, polypropylene glycol biscarboxymethyl ether dimethyl ester, glycerin polyethylene glycol triacetic acid ester, pentaerythritol polyethylene glycol tetraacetic acid ester, pentitol polyethylene glycol pentaacetic acid ester, sorbitol polyethylene Such as glycol hexa acetate are preferred examples.

As the aliphatic polyethers having an amide group at the terminal, at least one terminal of the above-mentioned alkylene glycols is converted to carboxymethyl ether and then amidated, or after the hydroxy terminal is modified with an amino group. Examples thereof include a method for amidation. Specifically, polyethylene glycol bis (carboxymethyl ether dimethylamide), polypropylene glycol bis (carboxymethyl ether dimethylamide), polyethylene glycol bis (carboxymethyl ether diethylamide), glycerin polyethylene glycol Tricarboxymethyl ether dimethylamide, pentaerythritol polyethylene glycol Tetracarboxymethyl ether dimethylamide, pentitol polyethylene glycol Printer carboxymethyl ether dimethylamide, sorbitol polyethylene glycol hexa carboxymethyl ether dimethylamide is preferably used.

Examples of the aliphatic polyethers having an alkyl carbonate group at the terminal include a method of attaching a formyl ester group to at least one terminal of the above alkylene glycol, and specifically, bismethoxycarbonyloxy polyethylene. Examples thereof include glycol, bisethoxycarbonyloxy polyethylene glycol, bisethoxycarbonyloxy polypropylene glycol, bis-tert-butoxycarbonyloxy polyethylene glycol and the like. Further, aliphatic polyethers modified with a urethane group or a trialkylsilyl group at the terminal can also be used. In the trialkylsilyl modification, trimethylsilyl modification is particularly preferable, and it can be modified with trimethylchlorosilane, trimethylchlorosilylacetamide or hexamethyldisilazane.

Examples of aliphatic polyesters include polycondensates of hydroxycarboxylic acids such as polyglycolide, polycaprolactone and polypivalolactone, and ring-opening polymers of lactones, and polyethylene oxalate, polyethylene succinate, polyethylene adipate. A polycondensation product of a dicarboxylic acid such as polyethylene sebacate, polypropylene adipate, and polyoxydiethylene adipate with an alkylene glycol, and a ring-opening copolymerization product of an epoxide and an acid anhydride, wherein at least one terminal of the polymer is Examples thereof include those modified with an alkyl ether group, an alkyl ester group, an alkylamide group, an alkyl carbonate group, a urethane group, or a trialkylsilyl group.

Examples of aliphatic polycarbonates include polycarbonates such as polyethylene carbonate, polypropylene carbonate, polypentamethylene carbonate, polyhexamethylene carbonate as the main chain portion, and at least one terminal of the polymer has an alkyl ether group. , Those modified with an alkyl ester group, an alkyl amide group, an alkyl carbonate group, a urethane group, and a trialkylsilyl group.

Examples of aliphatic polyanhydrides include dicarboxylic acids such as polymalonyl oxide, polyadipoyl oxide, polypimeloyl oxide, polysuberoyl oxide, polyazela oil oxide, and polysebacyl oxide as the main chain portion. The polycondensate of the polymer may be mentioned, and at least one end of the polymer modified with an alkyl ether group, an alkyl ester group, an alkylamide group, an alkyl carbonate group, a urethane group or a trialkylsilyl group. You can Further, in the present invention, an organic polymer having at least one polymerizable functional group in the molecule can also be used. The reason for using such a polymer is not clear, but
The strength of the porous thin film is improved.

As the polymerizable functional group, vinyl group, vinylidene group, vinylene group, glycidyl group, allyl group, acrylate group, methacrylate group, acrylamide group, methacrylamide group, carboxyl group, hydroxyl group,
Examples thereof include an isocyanate group, an amino group, an imino group and a halogen group. These functional groups can be in the main chain of the polymer, at the ends or at the side chains. Further, it may be directly bonded to the polymer chain or may be bonded via a spacer such as an alkylene group or an ether group. The same polymer molecule may have one type of functional group or two or more types of functional groups. Among the functional groups listed above, vinyl group, vinylidene group, vinylene group, glycidyl group, allyl group, acrylate group, methacrylate group, acrylamide group, and methacrylamide group are preferably used. As the organic polymer, it is particularly preferable to use a polymer containing an aliphatic polyether, an aliphatic polyester, an aliphatic polycarbonate, or an aliphatic polyanhydride having a low thermal decomposition temperature as a main constituent, as in the above-mentioned examples of the polymer.

The basic skeleton of the organic polymer having a polymerizable functional group that can be used in the present invention will be shown more specifically.
In the following, alkylene refers to methylene, ethylene, propylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, isopropylidene, 1,2-dimethylethylene, 2,2-dimethyltrimethylene,
The alkyl here includes an alkyl group having 1 to 8 carbon atoms and an aryl group such as a phenyl group, a tolyl group, and an anisyl group, (meth) acrylate refers to both acrylate and methacrylate, and dicarboxylic acid is oxalic acid, Malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid,
Refers to organic acids such as suberic acid, azelaic acid, and sebacic acid.

(A) Polyalkylene glycol (meth)
Acrylate, polyalkylene glycol di (meth) acrylate, polyalkylene glycol alkyl ether (meth) acrylate, polyalkylene glycol vinyl ether, polyalkylene glycol divinyl ether, polyalkylene glycol alkyl ether vinyl ether, polyalkylene glycol glycidyl ether, polyalkylene glycol diglycidyl An aliphatic polyether having a polymerizable functional group such as an acrylate group, a methacrylate group, a vinyl group and a glycidyl group at the end, which is represented by ether, polyalkylene glycol alkyl ether glycidyl ether and the like.

(B) Polycaprolactone (meth) acrylate, polycaprolactone vinyl ether, polycaprolactone glycidyl ether, polycaprolactone vinyl ester, polycaprolactone glycidyl ester, polycaprolactone vinyl ester (meth) acrylate, polycaprolactone glycidyl ester (meth) acrylate, Polycaprolactone vinyl ester vinyl ether, polycaprolactone glycidyl ester vinyl ether, polycaprolactone vinyl ester glycidyl ether, polycaprolactone glycidyl ester glycidyl ether, etc., acrylate group, methacrylate group at one end or both ends,
Polycaprolactone having a polymerizable functional group such as a vinyl group or a glycidyl group.

(C) Polycaprolactone triol (meth) acrylate, di (meth) acrylate, tri (meth) acrylate, vinyl ether, divinyl ether, trivinyl ether, glycidyl ether, diglycidyl ether, triglycidyl ether. (D) An aliphatic polyester which is a polymer of dicarboxylic acid and alkylene glycol and has a polymerizable functional group such as an acrylate group, a methacrylate group, a vinyl group or a glycidyl group at one or both ends. (E) An aliphatic polyalkylene carbonate having a polymerizable functional group such as an acrylate group, a methacrylate group, a vinyl group or a glycidyl group at one end or both ends.

(F) An aliphatic polyanhydride which is a polymer of dicarboxylic acid anhydride and has a polymerizable functional group such as an acrylate group, a methacrylate group, a vinyl group and a glycidyl group at the terminal. (G) Polyglycidyl (meth) acrylate, polyallyl (meth) acrylate, polyvinyl (meth) acrylate and the like, polyacrylic acid ester and polymethacrylic acid ester having a functional group such as vinyl group, glycidyl group and allyl group in the side chain. (H) Polyvinyl cinnamate, polyvinyl azidobenzal, epoxy resin and the like are used.

The organic polymer which can be used in the present invention has been described above. The molecular weight of the organic polymer is 100 to 1,000,000, preferably 100 to 300,000 in number average.
More preferably, it is 200 to 50,000. When the molecular weight is 100 or less, the organic polymer is removed from the composite of silica and the organic polymer too quickly to obtain a porous silica thin film having a desired porosity, and the polymer molecular weight is If it exceeds 1,000,000, the removal rate of the polymer is too slow and the polymer remains, which is not preferable. In particular, the more preferable molecular weight of the polymer is 200 to
It is 50,000, and in this case, a porous silica thin film having a desired high porosity can be extremely easily obtained at a low temperature in a short time. It should be noted here that the pore size of the porous silica is extremely small and uniform without much depending on the molecular weight of the polymer.

The molecular weight of each block of the block copolymer used in the present invention is 100 to 100,000, preferably 100 to 100.
It is 50,000, more preferably 200 to 20,000. Molecular weight is 1
When it is 00 or less or 100,000 or more, an appropriate compatibility is not obtained between the silica precursor and the polymer, so that the mechanical strength of the porous silica thin film is not expressed. The amount of the organic polymer added in the present invention is 0.01 to 10 parts by weight, preferably 0. 0 parts by weight, based on 1 part by weight of the siloxane obtained assuming that the total amount of the starting alkoxysilane charged has undergone hydrolysis and condensation reactions. 05-5 parts by weight, more preferably 0.5-
3 parts by weight. If the addition amount of the organic polymer is less than 0.01 part by weight, a porous body cannot be obtained, and even if it is more than 10 parts by weight, porous silica having sufficient mechanical strength cannot be obtained, resulting in poor practicability. The siloxane obtained by assuming that the total amount of alkoxysilane charged has undergone a hydrolysis and condensation reaction means that 100% of the OR ¹ groups bonded to Si in the general formulas (1) and (2) are hydrolyzed to SiOH. , Which is 100% condensed to have a siloxane structure.

Next, the solvent (C) that can be used in the present invention will be explained. The solvent (C) that can be used in the present invention is at least one solvent selected from the group consisting of alcohol solvents, ketone solvents, amide solvents and ester solvents, and the silica precursor and the organic polymer are solvents. It is dissolved or dispersed in. Here, examples of the alcohol solvent include methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, sec-butanol, t-butanol, n-pentanol, i-pentanol and 2-methyl. Butanol,
sec-pentanol, t-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2-ethylbutanol,
sec-heptanol, heptanol-3, n-octanol,

2-ethylhexanol, sec-octanol, n-nonyl alcohol, 2,6-dimethylheptanol-4, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-hepta Monoalcohol solvents such as decyl alcohol, phenol, cyclohexanol, methylcyclohexanol, 3,3,5-trimethylcyclohexanol, benzyl alcohol, diacetone alcohol, and ethylene glycol,
1,2-propylene glycol, 1,3-butylene glycol, pentanediol-2,4,2-methylpentanediol-2,4, hexanediol-2,5, heptanediol-2,4,2-ethylhexanediol −
1,3, diethylene glycol, dipropylene glycol, triethylene glycol,

Polyhydric alcohol solvents such as tripropylene glycol, and ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, ethylene Glycol mono-2-ethylbutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopro Ether, propylene glycol monobutyl ether, can be cited dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, polyhydric alcohol partial ether solvents such as dipropylene glycol monopropyl ether and the like. These alcohol solvents may be used either individually or in combination of two or more.

Of these alcohols, n-propanol, i-propanol, n-butanol, i-butanol, sec-butanol, t-butanol, n-pentanol, i-pentanol, 2-methylbutanol, s.
ec-pentanol, t-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2-ethylbutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether. , Propylene glycol monobutyl ether and the like are preferable.

As the ketone solvent, acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-
n-butyl ketone, diethyl ketone, methyl-i-butyl ketone, methyl-n-pentyl ketone, ethyl-n-
Butyl ketone, methyl-n-hexyl ketone, di-i-
Butyl ketone, trimethylnonanone, cyclohexanone, 2-hexanone, methylcyclohexanone, 2,4
-Pentanedione, acetonylacetone, acetophenone, fenchon, etc., acetylacetone, 2,
4-hexanedione, 2,4-heptanedione, 3,5
-Heptanedione, 2,4-octanedione, 3,5-
Octanedione, 2,4-nonanedione, 3,5-nonanedione, 5-methyl-2,4-hexanedione, 2,
2,6,6-tetramethyl-3,5-heptanedione,
Examples include β-diketones such as 1,1,1,5,5,5-hexafluoro-2,4-heptanedione.
These ketone solvents may be used either individually or in combination of two or more.

As the amide solvent, formamide, N
-Methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, acetamide, N-methylacetamide, N,
N-dimethylacetamide, N-ethylacetamide,
Examples include N, N-diethylacetamide, N-methylpropionamide, N-methylpyrrolidone, N-formylmorpholine, N-formylpiperidine, N-formylpyrrolidine, N-acetylmorpholine, N-acetylpiperidine, N-acetylpyrrolidine and the like. To be These amide solvents may be used either individually or in combination of two or more.

Ester solvents include diethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, methyl acetate, ethyl acetate, γ-butyrolactone, γ.
-Valerolactone, n-propyl acetate, i-propyl acetate, n-butyl acetate, i-butyl acetate, sec-butyl acetate, n-pentyl acetate, sec-pentyl acetate, 3-methoxybutyl acetate, methylpentyl acetate, acetic acid 2-ethylbutyl, 2-ethylhexyl acetate, benzyl acetate,
Cyclohexyl acetate, methyl cyclohexyl acetate, n-nonyl acetate, methyl acetoacetate, ethyl acetoacetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol mono-acetate
n-butyl ether,

Propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate,
Propylene glycol monopropyl ether acetate, propylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, glycol diacetate,
Methoxytriglycol acetate, ethyl propionate, n-butyl propionate, i-amyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate,
Examples thereof include ethyl lactate, n-butyl lactate, n-amyl lactate, diethyl malonate, dimethyl phthalate, and diethyl phthalate. These ester solvents may be used either individually or in combination of two or more.

It is preferable to use an alcohol solvent and / or an ester solvent as the solvent (C), because a composition having good coating properties and storage stability can be obtained. The coating composition of the present invention contains the above solvent (C), but a similar solvent can be additionally added when the silica precursor (A) is hydrolyzed and / or condensed. In the present invention, an acid may be added to the coating composition.

Specific examples of the acid that can be used in the present invention include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, tripolyphosphoric acid, phosphonic acid and phosphinic acid. As the organic acid, for example, acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, oxalic acid,
Maleic acid, methylmalonic acid, adipic acid, sebacic acid, gallic acid, butyric acid, meritic acid, arachidonic acid, shikimic acid, 2-ethylhexanoic acid, oleic acid, stearic acid, linoleic acid, linoleic acid, salicylic acid, benzoic acid, p-aminobenzoic acid, p-toluenesulfonic acid, benzenesulfonic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, trifluoroacetic acid, formic acid, malonic acid, sulfonic acid, phthalic acid, fumaric acid, citric acid, tartaric acid, succinic acid , Isonicotinic acid, etc.

Further, a compound which functions as an acid after the coating solution of the present invention is coated on a substrate is also included. Specific examples thereof include compounds such as aromatic sulfonic acid esters and carboxylic acid esters that decompose by heating or light to generate an acid. The acid may be used alone or in combination of two or more kinds. The addition amount of these acid components is 1 mol or less, preferably 0.1 mol or less, relative to 1 mol of the OR ¹ group of the general formulas (1) and (2) charged as starting materials. If it is more than 1 mol, a precipitate may be generated, and it may be difficult to obtain a coating film made of a homogeneous porous silicon oxide.

The coating composition of the present invention described above is prepared from a tetrafunctional alkoxysilane or the like by combining a specific amount of the trifunctional alkoxysilane or the like, a polyether block copolymer and an acid. The relative permittivity of the formed porous silica thin film can be remarkably lowered. Although the reason for this is not clear, silanol groups (silanol groups that are water-absorbing and cause a significant increase in the dielectric constant of the thin film) that are silica end groups present in the composite or porous body and the trifunctionality It is presumed that the silanol group is deactivated by promoting the reaction of the above with the alkoxysilane and the like by the action of the polyether block copolymer and the acid. In addition, if desired, components such as colloidal silica and ionic and nonionic surfactants may be added, and a photocatalyst generator for imparting photosensitivity and adhesion to the substrate may be enhanced. It is also possible to add arbitrary additives such as an adhesion improver for the purpose and a stabilizer for long-term storage to the coating composition of the present invention within a range not impairing the gist of the present invention.

Next, a method for producing the coating composition of the present invention will be described. The coating composition of the present invention can be obtained by mixing the above-mentioned alkoxysilane and an organic polymer. At least a part of the alkoxysilane is hydrolyzed and polycondensed so that the hydrolyzate of the alkoxysilane becomes an oligomer. Condensation is preferable. Since hydrolysis and polycondensation increase the viscosity of the coating composition to an appropriate level,
The shape retention of the coating film can be ensured and the film thickness can be made uniform. Furthermore, when the silica precursor gels into silica, the formation of the silica skeleton occurs mildly, so that the film shrinkage hardly occurs. This is because. Therefore, the alkoxysilane is treated under the following constant conditions. It should be noted that the treatment of the alkoxysilane may be carried out after mixing the alkoxysilane and the organic polymer, but it is also possible to pretreat the alkoxysilane and then mix the organic polymer.

In the present invention, the treatment conditions for alkoxysilane are usually 0 to 150 ° C. in the presence of water necessary for hydrolysis.
Preferably 0-100 ° C, more preferably 0 ° C-50 ° C
You can process with. When the temperature is lower than 0 ° C, the progress of hydrolysis is not sufficient, and when the temperature is higher than 150 ° C, the reaction rapidly proceeds excessively and gelation of the solution may occur, which is not preferable. As mentioned above, hydrolysis also includes partial hydrolysis. For example, in the case of tetrafunctional alkoxysilane,
It is not necessary for all four alkoxy groups to be hydrolyzed, eg only one is hydrolyzed, 2
One or more of them may be hydrolyzed, or a mixture thereof may be present.

In the polycondensation, silanol groups obtained by hydrolysis of alkoxysilane are condensed to produce Si--O--S.
Although i-bonds are formed, it is not necessary that all silanol groups are condensed, and some silanol groups may be condensed, and the degree of condensation is represented by the condensation rate. The condensation rate of the alkoxysilane in the coating composition of the present invention is 10 to 90%, preferably 20 to 85%, more preferably 30 to 85%. This condensation rate can be determined by the ²⁹ Si-NMR method in a solution state. When the condensation rate is lower than 10%, the viscosity of the coating solution becomes insufficient, the shape retention of the coating film cannot be ensured, and the film thickness cannot be made uniform. Also,
Since gelation occurs rapidly when silica is formed, film shrinkage easily occurs. On the other hand, if the condensation rate exceeds 90%, the entire coating composition will gel. In the present invention, the condensation rate can be expressed as the ratio of the functional groups involved in the siloxane bond among the functional groups of the alkoxysilane used as the raw material of the coating composition.

The water required for the hydrolysis of the alkoxysilane used in the present invention is generally added as a liquid or as an aqueous solution of alcohol or the like, but it may be added in the form of steam. When water is rapidly added, depending on the type of alkoxysilane, hydrolysis and condensation may be too fast and precipitation may occur. Therefore, it is preferable to add water for a sufficient time. Therefore, when the liquid is added, it is preferable to use a method in which a solvent such as alcohol coexists so that the alkoxysilane uniformly contacts with water, or a method of adding at a low temperature is used alone or in combination. The amount of water added is preferably in the range of 0.1 mol to 5 mol per 1 mol of the alkoxysilane group charged as the raw material. When the amount of water added is in this range, the following reaction proceeds smoothly, which is preferable.

The alkoxysilane treated under the above conditions is hydrolyzed to silanol in the presence of water, and then grows to an oligomeric silica precursor having a siloxane bond by a condensation reaction between silanol groups. Further, it is preferable that the content of alkali metals such as sodium and potassium and iron in the coating composition is 50 ppb or less, particularly 10 ppb or less from the viewpoint of low leak current of the coating film.
The alkali metal and iron may be mixed from the raw materials used, and it is preferable to purify the silica precursor (A), the organic polymer (B), the solvent (C) and the like by distillation or the like. In the present invention, a composite thin film of silica and an organic polymer can be obtained by using the coating composition obtained as described above as a coating liquid and gelling the silica precursor in the obtained coating film.

Hereinafter, a method for coating the coating composition of the present invention to obtain a thin film, a method for gelating the thin film to form a composite thin film, and a method for removing an organic polymer from the composite thin film will be described in detail. . The total solid content concentration of the coating composition in the present invention is preferably 2 to 30% by weight as described above, but is appropriately adjusted according to the purpose of use. When the total solid content concentration of the coating composition is 2 to 30% by weight, the film thickness of the coating film is in an appropriate range and the storage stability is further excellent. The total solid content concentration is adjusted, if necessary, by concentration or dilution with the solvent (C). The total solid content concentration is determined as the weight% of the siloxane compound obtained by hydrolysis and condensation reaction of the total amount of alkoxysilane with respect to a known amount of coating composition.

In the present invention, the thin film is formed by coating the substrate with the coating composition of the present invention. As a coating method, known methods such as casting, dipping, and spin coating can be used, but spin coating is suitable for use in manufacturing an insulating layer for a multilayer wiring structure of a semiconductor element. The thickness of the thin film can be controlled in the range of 0.1 μm to 100 μm by changing the viscosity and the rotation speed of the coating composition. If it is thicker than 100 μm, cracks may occur. As an insulating layer for a multilayer wiring structure of a semiconductor element,
Usually, it is used in the range of 0.1 μm to 5 μm.

As the substrate, a semiconductor substrate of silicon, germanium or the like, a compound semiconductor substrate of gallium-arsenic, indium-antimony or the like can be used, and a thin film of another substance is formed on the surface thereof before use. Is also possible. In this case, as the thin film, in addition to metals such as aluminum, titanium, chromium, nickel, copper, silver, tantalum, tungsten, osmium, platinum and gold, silicon dioxide, fluorinated glass, phosphorus glass, boron-phosphorus glass, borosilicate. Acid glass, polycrystalline silicon, alumina,
Inorganic compounds such as titania, zirconia, silicon nitride, titanium nitride, tantalum nitride, boron nitride, hydrogenated silsesquioxane, methyl silsesquioxane, amorphous carbon, fluorinated amorphous carbon, polyimide, and any other block copolymer Thin films can be used.

Prior to the formation of the thin film, the surface of the substrate is
It may be previously treated with an adhesion improver. As the adhesion improver in this case, those used as so-called silane coupling agents, aluminum chelate compounds and the like can be used. Particularly preferably used are 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N-
(2-Aminoethyl) -3-aminopropylmethyldimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropylmethyldichlorosilane, 3-chloropropylmethyldimethoxysilane, 3- Chloropropylmethyldiethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyl Dimethoxysilane, hexamethyldisilazane, ethyl acetoacetate aluminum diisopropylate, aluminum tris (ethyl acetoacetate), aluminum bis (ethyl acetoacetate) G) monoacetylacetonate, and the like of aluminum tris (acetylacetonate). When applying these adhesion improvers, other additives may be added, if necessary, or diluted with a solvent. The treatment with the adhesion improver is performed by a known method.

The gelling temperature to be subsequently applied after forming the coating composition into a coating film is not particularly limited, but is usually 100 to 30.
0 ° C., preferably 150 to 300 ° C. The time required for the gelation reaction varies depending on the heat treatment temperature, the amount of catalyst added and the solvent species and amount, but is usually in the range of several seconds to 10 hours. Preferably 30 seconds to 5 hours, more preferably 1
Minutes to 2 hours. By this operation, the gelation reaction of the silica precursor in the coating composition sufficiently progresses to form silica.
The condensation rate of silica can reach up to nearly 100%, but is usually about 90%. The condensation rate of this thin film is
It can be obtained by R. When the temperature is lower than 100 ° C., the polymer starts to be removed before the gelation sufficiently progresses in the polymer removal step which is a post-step, resulting in the densification of the coating film. Again 300
If the temperature is higher than 0 ° C, huge voids are likely to be formed, and the homogeneity of the composite thin film of silica and organic polymer described later will deteriorate.

Since the composite thin film of silica and organic polymer thus obtained has a relatively low dielectric constant and is capable of forming a thick film, it can be used as it is as an insulating portion of wiring, or it can be used as a thin film other than a thin film. Can also be used as an optical film, a structural material, a film, a coating material and the like. However, in order to obtain a material having a lower dielectric constant as an insulator for LSI multilayer wiring,
It is preferably converted into a porous silica thin film.

From the composite thin film of silica and organic polymer to the insulating porous silica thin film, the polymer is removed from the composite thin film of silica and organic polymer.
At this time, if the gelation reaction of the silica precursor has proceeded sufficiently, the region occupied by the organic polymer in the composite thin film of silica and the organic polymer does not collapse as voids in the porous silica thin film. Remain in. As a result, a porous silica thin film having a high porosity and a low dielectric constant can be obtained.

As a method for removing the organic polymer, heating, plasma treatment, solvent extraction and the like can be mentioned, but heating is most preferable from the viewpoint that it can be easily carried out in the current semiconductor element manufacturing process. In this case, the heating temperature depends on the type of the organic polymer used, and may be simply evaporated and removed in a thin film state, may be removed by firing with decomposition of the organic polymer, and may be a mixture thereof. The heating temperature is in the range of 300 to 450 ° C, preferably 350 to 400 ° C. If the temperature is lower than 300 ° C., the removal of the organic polymer is insufficient and impurities of the organic matter remain, so that there is a risk that a porous silica thin film having a low dielectric constant cannot be obtained. Also, the amount of pollutant gas generated is large. Conversely, 450
Treatment at a temperature higher than ° C is preferable from the viewpoint of removing the organic polymer, but it is extremely difficult to use in the semiconductor manufacturing process.

The heating time is preferably 10 seconds to 24 hours. It is preferably 10 seconds to 5 hours, and particularly preferably 1 minute to 2 hours. If it is shorter than 10 seconds, evaporation and decomposition of the organic polymer do not proceed sufficiently, so that organic substances remain as impurities in the obtained porous silica thin film, and the dielectric constant is not lowered as expected as a porous thin film. Moreover, since the thermal decomposition and the evaporation are usually completed within 24 hours, heating for a longer time does not make much sense.

Heating is preferably carried out in an inert atmosphere of nitrogen, argon, helium or the like. It is also possible to carry out in an oxidizing atmosphere such as mixing air or oxygen gas, but in this case, the concentration of the oxidizing gas is set so that the organic polymer is substantially decomposed before the silica precursor is gelated. It is preferable to control the concentration so that it does not occur. Further, by allowing ammonia, hydrogen, etc. to exist in the atmosphere to deactivate the silanol groups remaining in the silica, it is possible to reduce the hygroscopicity of the porous silica thin film and suppress an increase in the dielectric constant.

Since the amount of residual polymer in the porous silica thin film after removing the organic polymer of the present invention under the above heating conditions is remarkably reduced, the adhesive force of the upper layer film due to the decomposition gas of the organic polymer as described above. Phenomenon such as deterioration of the surface and peeling does not occur. The effect becomes more remarkable when the organic polymer in the coating composition of the present invention includes the polyether block copolymer and the polymer having a terminal group that is chemically inactive to the silica precursor. As long as the present invention performs the step of forming a composite thin film of silica and an organic polymer and then the step of removing the polymer under the above-mentioned conditions, there is no problem even if a step with an arbitrary temperature or atmosphere is performed before and after the step. There is no. For heating in the present invention, a single wafer type vertical furnace or a hot plate type firing system which is usually used in the semiconductor element manufacturing process can be used. Of course, it is not limited to these as long as the manufacturing process of the present invention is satisfied.

As described above, by using the porous silica thin film of the present invention, it is possible to form an insulating film for a multilayer wiring for LSI, which has a high mechanical strength and a sufficiently low dielectric constant. The relative permittivity of the porous silica thin film of the present invention can usually achieve 2.8 to 1.2. This relative dielectric constant can be adjusted by the content of the component (B) in the coating composition of the present invention. Further, in the porous thin film of the present invention, pores of 20 nm or more are not substantially observed in the pore distribution measurement by the BJH method, and it is suitable as an interlayer insulating film. The porous silica thin film obtained by the present invention is a bulk porous silica body other than a thin film, for example, an optical film such as an antireflection film or an optical waveguide, a catalyst carrier, a heat insulating material, an absorbent, a column packing material, or a caking material. It can also be used as an inhibitor, a thickener, a pigment, an opacifying agent, a ceramic, a smoke suppressant, an abrasive, a dentifrice and the like.

[0075]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to Examples and Comparative Examples, but the scope of the present invention is not limited to these Examples. Evaluation of the coating composition and thin film for producing an insulating thin film was carried out by the following methods. The evaluation results of each example and comparative example are shown in Table 1. (1) is a quantitative invention of silicon atoms silicon atoms from different alkoxysilanes having functional groups contained in the coating composition each ²⁹ Si-
Expressed by the numerical value calculated from the area of the signal by NMR,
By comparing them, the composition ratio of the alkoxysilane or the like contained in the coating composition is obtained.

As an example, a method of calculating the mol% of silicon atoms due to MTES in the composition when tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) are used as the alkoxysilane will be described. Device: JEOL-Lambda 400 Measurement mode: NNE Sample tube: Outer diameter 10 mm, Inner diameter 3 mm (Coating composition, thin film added D ethanol, small amount of TMS) Accumulation frequency: 1300 times PD (pulse delay) 250 seconds BF (broad) 30 Hz)

It is calculated by the following formula using the numerical values obtained from the above measuring device and measuring conditions. MTES mol% = 100 × (M0 + M1 + M2 + M
3) / {(T0 + T1 + T2 + T3 + T4) + (M0 +
M1 + M2 + M3)} (In the formula, T0 and M0 are TE of the raw material in the above-mentioned device, respectively.
OS and MTES themselves, or at least one of the respective ethoxy groups is a signal integrated intensity attributed to the compound hydrolyzed to a hydroxyl group, T
1, M1 represents an integrated intensity of a signal attributed to a group formed by bonding one Si site of TEOS and MTES to an adjacent Si atom through an oxygen atom, and T2 and M2.
Represents the integrated intensity of a signal attributed to a group formed by bonding two Si sites in TEOS and MTES to adjacent Si atoms via oxygen atoms, and T3 and M3 represent TE.
Three parts of Si in OS and MTES represent an integrated intensity of a signal attributed to a group formed by bonding to adjacent Si atoms via oxygen atoms, and T4 represents four adjacent parts of Si in TEOS. Represents the integrated intensity of the signal that is assigned to the group formed by bonding through the Si atom and the oxygen atom)

(2) Relative permittivity It was measured using an SSM495 type automatic mercury CV measuring device manufactured by Solid State Measurement Company. (3) Film thickness measurement It was measured using RINT 2500 manufactured by Rigaku Denki. The measurement conditions are
Divergence slit: 1/6 °, Scattering slit: 1/6 °, Detector slit: 0.15mm Detector (scintillation counter)
A graphite monochromator was set in front of. Tube voltage and tube current were measured at 40kV and 50mA, respectively, but can be varied as needed. The goniometer scanning method was a 2θ / θ scanning method, and the scanning step was 0.02 °.

(4) Young Modulus Nano Indenter DCM manufactured by MTS Systems Corporation
It was measured at. The measurement method is as follows. A Burkovich type diamond indenter is pushed into the inside of a porous silica thin film having a film thickness of 0.7 to 1 μm formed on a substrate, a constant load is applied and then the displacement is monitored, and the displacement is monitored. Then the load-displacement curve was obtained. The surface was recognized under the condition that the contact stiffness was 200 N / m. The hardness is calculated by the following formula. H = P / A Here, P is the applied load, and the contact area A is a function of the contact depth hc and was experimentally obtained by the following equation.

[Equation 1]

This contact depth has the following relationship with the displacement h of the indenter. hc = h-εP / S where ε is 0.75 and S is the initial slope of the unloading curve. The Young's modulus was calculated by Sneddon's formula. Er = (√π · S) / 2√A Here, the composite elastic modulus Er is expressed by the following equation. ^{Er = [(1-νs 2} ) / Es + (1-νi 2) / Ei] -1 where, [nu is the Poisson's ratio, the subscript S samples, i is representative of the indenter. In the present invention, ν i = 0.07, Ei = 1141 G
Pa, and the Poisson's ratio of this material is unknown, but νs =
The Young's modulus Es of the sample was calculated as 0.18.

(5) Adhesion Strength ER was applied to the porous silica thin film formed on the silicon wafer.
An ICHSEN Cross Hatch Cutter was pressed against the coating film while keeping it at 20 degrees, and a 100 mm square-shaped cut with a width of 1 mm was made at a speed of 2 to 5 seconds / 10 cm. Stick a cellophane adhesive tape with a width of 18 mm and an adhesive strength of 2.94 N / 10 mm or more on the grid,
After completely adhering the tape to the coating film, hold the tape at one end and keep it at a right angle to the coated surface, and peel it off momentarily. The state of cross-shaped scratches was observed and evaluated according to the score of the cross-cut test described in JIS K-5400 Adhesion. (6) Water Absorption The IR spectra of the thin film before and after the porous silica thin film of the present invention was left at 110 ° C. under 100% saturated vapor for 1 hour were compared, and the presence or absence of absorption due to water around 3500 cm ^{−1 was} checked. It was examined, and when there was no absorption, it was evaluated as ○, and when there was absorption, it was evaluated as X.

[0082]

Example 1 Tetraethoxysilane 7.92 g, Methyltriethoxysilane 4.04 g, Ethanol 23.5
g, water 16.1 g, and a mixture of 0.1 mol / l nitric acid 3.3 g, and polyethylene glycol / polypropylene glycol / polyethylene glycol dimethoxy having both end groups methoxylated (number average molecular weight 6430, number average of polypropylene glycol moiety). The molecular weight is 3200) 2.
28 g was added and reacted at 40 ° C. for 6 hours with stirring. The resulting solution was concentrated under reduced pressure to 17.1 g, then propylene glycol monomethyl ether (15.0 g) and water (1).
6.0 g was added to prepare a coating composition of the present invention.
The Si atom derived from methyltriethoxysilane in the obtained coating solution of the present invention was 37 mol%.

This solution was coated on a 6-inch silicon wafer by 3 times.
ml was dropped and spin coated at 1050 rpm for 60 seconds. Then, in air at 120 ° C for 1 minute under nitrogen atmosphere 2
1 hour at 00 ° C, then 1 hour at 400 ° C under nitrogen atmosphere
It was heated and baked for a time to obtain a porous silica thin film having a film thickness of 0.85 μm. The relative permittivity at 1 MHz in the obtained thin film was 2.2, and the Young's modulus was 6.6 GPa. The adhesion was 10 points (highest point) and the water absorption was ◯.

[0084]

Example 2 Instead of using 2.28 g of polyethylene / polypropylene glycol / polyethylene glycol having both ends methoxylated in Example 1, 0.25 g of the block copolymer and 1.66 g of polyethylene glycol dimethyl ether (number average molecular weight 600) were used. And add
Further, a coating composition of the present invention was obtained in the same manner as in Example 1 except that 0.25 g of a 0.9 wt% aqueous solution of oxalic acid was added instead of nitric acid. The Si atom derived from methyltriethoxysilane in the composition was 37 mol%. This solution was treated in the same manner as in Example 1 to obtain a porous silica thin film having a thickness of 0.78 μm. The obtained thin film has a relative permittivity of 2.3 at 1 MHz and a Young's modulus of 7.1 GP.
It was a. The adhesion was 10 points (highest point) and the water absorption was ◯.

[0085]

EXAMPLE 3 Instead of adding 2.28 g of polyethylene glycol / polypropylene glycol / polyethylene glycol dimethoxy (number average molecular weight 6430, number average molecular weight of polypropylene glycol part is 3200) having both end groups methoxylated in Example 1 instead of 2.28 g. A coating composition of the present invention was obtained in the same manner as in Example 1 except that 0.3 g of the block copolymer and 2.0 g of polyethylene glycol dimethyl ether (number average molecular weight 600) were added. Si derived from methyltriethoxysilane in the composition
The atom was 37 mol%. This solution was subjected to the same operation as in Example 1 to obtain a porous silica thin film having a film thickness of 0.75 μm. The relative permittivity at 1 MHz in the obtained thin film was 2.2, and the Young's modulus was 6.0 GPa. The adhesion was 10 points (highest point) and the water absorption was ◯.

[0086]

Comparative Example 1 The same operation as in Example 1 was performed except that 2.28 g of polyethylene glycol dimethyl ether (number average molecular weight 600) was used in place of methoxylated polyethylene glycol / polypropylene glycol / polyethylene glycol. , Film thickness is 0.77
A porous silica thin film of μm was obtained. The adhesion of the obtained thin film was 10 points, but the water absorption was x, the relative dielectric constant at 1 MHz was 3.0, and the Young's modulus was 2.9 GPa, which was higher than that of Example 1. The mechanical strength was low.

[0087]

Comparative Example 2 The coating liquid of this Comparative Example was prepared in the same manner as in Example 1 except that 3.82 g of tetraethoxysilane and 13.10 g of methyltriethoxysilane were used instead of the alkoxysilane used in Example 1. It was prepared (Si atom derived from methoxysilane was 80 mol%) to obtain a porous silica thin film. The thin film had a thickness of 0.85 μm, adhesion was 10 points, water absorption was good, and the relative dielectric constant was 2.3, but the Young's modulus was low at 3.4 GPa.

[0088]

[Table 1]

[0089]

INDUSTRIAL APPLICABILITY The porous silica thin film according to the present invention has a sufficiently low relative permittivity and is stable, can sufficiently withstand the CMP process in the copper wiring process of a semiconductor device, and has a small amount of pollutant gas generated during the formation of an LSI. It is most suitable for multi-layer wiring substrates and insulating films for semiconductor devices.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09D 171/02 C09D 171/02 183/04 183/04 H01L 21/312 H01L 21/312 C 21/316 21 / 316 G F-term (reference) 4G072 AA24 AA25 GG01 HH30 MM01 RR05 RR07 UU07 4J038 AA011 CQ001 CQ002 CQ011 CQ012 DF001 DF002 DL021 DL022 DL031 DL032 GA01 GA02 GA09 HA096 HA236 HA336 HA366 HA416 HA441 JA16 JA32 JA35 JA55 JB12 KA06 NA21 5F058 AA10 AC03 AF04 AG01 AH02 BA20 BC02 BF46 BH01 BJ02

Claims (7)

[Claims] 1. (A) An alkoxysilane represented by the following general formula (1) and at least one or more of a hydrolyzate and a polycondensate thereof, and an alkoxy represented by the following general formula (2). A silica precursor containing at least one or more of silane and its hydrolyzate and polycondensate, which is derived from an alkoxysilane represented by the general formula (1) and its hydrolyzate and polycondensate. 1 mol% of the silicon atom derived from the general formula (2) with respect to the total of the silicon atom derived from the general formula (2) and the alkoxysilane represented by the general formula (2) and its hydrolyzate and polycondensate. Si (OR ¹ ) ₄ ... (1) R ² (Si) (OR ¹ ) ₃ ... (2) (wherein R ¹ and R ² are: They may be the same or different, each of (B) an organic polymer containing a linear or branched binary or more block copolymer and (C) an alcohol solvent, a ketone solvent, an amide solvent and an ester solvent. A coating composition for producing an insulating thin film, which comprises at least one selected solvent. 2. The insulating thin film according to claim 1, wherein at least one of the end groups of the organic polymer is end-capped so as to be a group which is chemically inactive to the silica precursor. Coating composition for production. 3. The coating composition for producing an insulating thin film according to claim 1, wherein the organic polymer contains at least 1% by weight of the block copolymer. 4. The coating composition for producing an insulating thin film contains at least one kind of acid.
A coating composition for producing an insulating thin film according to any one of 1. 5. A silica-organic polymer composite thin film is obtained by applying a coating composition for producing an insulating thin film according to claim 1 on a substrate and then gelating a silica precursor. A porous insulating silica thin film obtained by subsequently removing an organic polymer from a composite thin film of silica and an organic polymer. 6. A wiring structure comprising the insulating silica thin film according to claim 5. 7. A semiconductor device including the wiring structure according to claim 6.