JP2006061762A - Method of forming silica type hardened coat, liquid for improving silica type hardened coat, the silica type hardened coat and electronic part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a silica type hardened coat having a dielectric constant comparable with, or lower than, that of conventional porous films and sufficiently high mechanical strength. <P>SOLUTION: The method has a first process of causing a liquid containing a first catalyst to permeate into a silica type coat formed on a substrate and a second process of hardening the coat after the treatment of the first process to obtain a silica type hardened coat. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for forming a silica-based cured coating, a silica-based cured coating improving liquid, a silica-based cured coating, and an electronic component.

  In recent years, in electronic device components such as semiconductor elements such as LSIs, the problem of wiring delay has become apparent, as the inter-wiring capacity increases and the signal propagation speed decreases as the degree of integration of integrated circuits increases and the element density increases. I have done it. For example, when the wiring interval of the electronic device component exceeds approximately 0.5 μm, the influence of the transistor delay on the entire device is rather dominant, and the influence of the wiring delay is relatively small. However, when the wiring interval becomes about 0.5 μm or less as LSI is highly integrated, the problem of wiring delay becomes more serious than transistor delay.

As a means for reducing the wiring delay problem, it is known to reduce the dielectric constant of an insulating material used for an electronic component. In general, the signal propagation speed (v) of the wiring and the relative dielectric constant (ε) of the insulating material in contact with the wiring material are expressed by the following formula (2):
v = k / √ε (2)
(K in the formula is a constant). That is, by increasing the frequency region to be used and reducing the relative dielectric constant (ε) of the insulating material, signal transmission speed can be increased. For example, conventionally, an SiO ₂ film formed by a CVD method having a relative dielectric constant of about 4.2 has been used as a material for forming an interlayer insulating film. However, recently, electronic parts having a wiring interval of 0.09 μm or less are also being put into practical use, and for such electronic parts having a wiring interval, an insulating material having a relative dielectric constant of about 2.4 or less is eagerly desired ( For example, refer nonpatent literature 1.).

  Examples of the low dielectric constant material having a relatively low dielectric constant include a SiOF film having a relative dielectric constant of about 3.5 formed by a CVD method, and an organic polymer having a relative dielectric constant of about 2.5 to 3.0 formed by a spin coating method. Examples of the film include silica films and silica films. Among these, a silica-based porous film having pores (voids) in the film is considered to be promising in order to achieve a dielectric constant (2.4 or less) that will be required in the future. Studies and developments for adopting as an interlayer insulating film have been actively conducted.

As a method for forming such a porous film, for example, Patent Document 1 proposes a reduction in dielectric constant of an organic SOG material. In this method, a film is formed from a composition containing a polymer having a property of volatilizing or decomposing by heating together with a hydrolytic condensation polymer of a metal alkoxide, and pores are formed by heating the film. Is.
JP-A-10-283443 "INTERNATIONAL TECHNOLOGY ROADMAP FOR SEMICONDUCTORS 2002 UPDATE", [online], Semiconductor Industry Association, [August 4, 2004 search], Internet <URL: http://public.itrs.net/Files/2002Update/2002Update.pdf >

  Conventional porous film forming methods such as those described in Patent Document 1 can realize a relatively low density of the porous film relatively easily, thereby reducing the relative dielectric constant of the porous film. However, the present inventors have studied in detail the method for forming such a conventional porous film. As a result, the mechanical strength of the porous film obtained by the conventional forming method is significantly higher than that of the film having no pores. I found it to decline. This decrease in mechanical strength is a major problem in process suitability, such as cohesive failure of the porous film due to stress during CMP, peeling near the interface with the layer adjacent to the porous film, and occurrence of defects in the packaging process. Will be generated.

  Accordingly, the present invention has been made in view of the above circumstances, and provides a method for forming a silica-based cured film having a relative dielectric constant equal to or lower than that of a conventional porous film and sufficiently excellent in mechanical strength. The purpose is to do. The present invention also provides a liquid for improving a silica-based cured film used in a method for forming a silica-based cured film, a silica-based cured film obtained by the forming method, and an electronic component including the silica-based cured film. Objective.

  The method for forming a silica-based cured film of the present invention includes a first step of allowing a liquid containing a first catalyst to penetrate into a silica-based coating formed on a substrate, and curing the silica-based coating after the first step. And a second step of obtaining a silica-based cured coating, wherein the surface tension of the silica-based coating is larger than the surface tension of the liquid.

  Here, the surface tension of the liquid is measured by a ring method under conditions of a temperature of 25 ° C. and a relative humidity of 40 to 60%.

  Although the factors that can solve the above problems by such a forming method are not clarified in detail at present, the present inventors consider the factors as follows. That is, in the conventional method for forming a porous film, it is difficult to obtain a porous film having a desired dielectric constant and mechanical strength because a part of the material contained in the raw material composition remains unreacted in the porous film. Presumed to be.

  On the other hand, according to the method for forming a silica-based cured film of the present invention, the silica-based film formed on the substrate is further processed using the liquid containing the first catalyst. The substance that remains unreacted is considered to decrease because it is converted into another substance by the catalytic action of the first catalyst. Therefore, it is possible to sufficiently suppress an increase in dielectric constant caused by the unreacted substance. In addition, it is estimated that the silica-based coating can be further cured by the penetration of the liquid containing the first catalyst. Thus, the present inventors believe that even if the silica-based coating (or silica-based cured coating) has pores, the mechanical strength is improved and the problems of the present invention can be achieved.

  In addition, when the silica-based cured film and the liquid have the above-described surface tension, the effect of suppressing the increase in the dielectric constant of the silica-based cured film and the effect of improving the mechanical strength can be sufficiently effectively exhibited. The inventors consider that this is due to the following factors, but the factors are not limited thereto. That is, since the above-described liquid has a surface tension smaller than that of the silica-based film, the liquid can sufficiently penetrate into, for example, pores inside the silica-based film. Therefore, the unreacted substance remaining in the silica-based coating is easily brought into contact with the first catalyst, and as a result, the effect of suppressing the increase in dielectric constant and improving the mechanical strength can be sufficiently effectively exhibited. It is done. From the same viewpoint, in the method for forming a silica-based cured film of the present invention, the surface tension of the liquid is preferably 21 mN / m or less.

  In the method for forming a silica-based cured film of the present invention, it is more preferable that the surface tension of the silica-based film is 5 mN / m or more larger than the surface tension of the liquid. As a result, the effect of suppressing the increase in the dielectric constant and the effect of improving the mechanical strength can be more effectively exhibited. This is presumed to be due to the fact that the liquid more easily penetrates into the silica-based coating.

  In the first step of the method for forming a silica-based cured coating according to the present invention, the method of infiltrating the liquid is a method of applying a liquid to the silica-based coating, a method of immersing the silica-based coating in the liquid, or a liquid in the silica-based coating. Any of the methods of spraying may be used.

  In the method for forming a cured silica film of the present invention, it is preferable that the liquid further contains a solvent. Thereby, since the dispersibility of the catalyst in the liquid is improved, the unreacted substance can be consumed more efficiently, and the mechanical strength of the silica-based cured coating can be increased.

  In the method for forming a silica-based cured film of the present invention, the first catalyst preferably exhibits a catalytic action for a dehydration condensation reaction between silanol groups. Thereby, the dielectric constant raise of a silica type cured film can further be suppressed, and the mechanical strength can be improved further. This is a compound having a silanol group that has a strong influence on the increase in the dielectric constant among the unreacted substances remaining in the silica-based film, and is used for a dehydration condensation reaction between silanol groups as a first catalyst. This is considered to be due to a decrease in the compound having a silanol group. In addition, the dehydration condensation reaction between silanol groups further increases the crosslink density in the silica-based cured film, so that it is considered that a silica-based cured film with higher mechanical strength can be obtained. However, the factors are not limited to these.

  In the method for forming a silica-based cured film of the present invention, the first catalyst contains one or more compounds selected from the group consisting of a first acidic compound, a first basic compound, and a first onium salt compound. It is preferable. Here, the first acidic compound excludes the acidic onium salt compound, and the first basic compound excludes the basic onium salt compound. These catalysts have the effect of further promoting the dehydration condensation reaction between unreacted silanol groups. From the same viewpoint, in the method for forming a silica-based cured film of the present invention, it is more preferable that the first basic compound has a nitrogen atom in the molecule.

  In the method for forming a silica-based cured film of the present invention, it is more preferable that the solvent contains a solvent having a fluorine atom in the molecule. Thereby, it is considered that the effect of suppressing the increase in the dielectric constant of the silica-based cured coating and the effect of improving the mechanical strength can be more effectively exhibited. This is presumably because the solvent having a fluorine atom in the molecule has a generally low surface tension and high permeability into the silica-based coating.

  In the method for forming a silica-based cured film of the present invention, it is more preferable that the silica-based cured film has pores. Such a silica-based cured film can have a lower dielectric constant. Moreover, as apparent from the above description, the silica-based cured coating has sufficient mechanical strength despite having pores.

In the method for forming a silica-based cured film of the present invention, the silica-based film is represented by the following formula (1);
R ¹ _n SiX _4-n (1)
Obtained by applying a composition for forming a silica-based film containing a siloxane resin obtained by hydrolytic condensation of a compound represented by formula (1) onto a substrate to form a coating film, and removing the solvent contained in the coating film. Is preferable. Here, in the formula (1), R ¹ is a group having a B atom, an N atom, an Al atom, a P atom, a Si atom, a Ge atom, or a Ti atom, an organic group having 1 to 20 carbon atoms, or an H atom or F represents an atom, X represents a hydrolyzable group, n represents an integer of 0 to 2, and when n is 2, each R ¹ may be the same or different, and when n is 0 to 2, Each X may be the same or different.

  When the silica-based film is formed, a silica-based film (Low-k film) exhibiting a low dielectric constant is formed by using the composition having such a configuration. In particular, in the present invention, a silica-based cured film having a lower dielectric constant and further excellent mechanical strength can be formed by a combined action with the liquid containing the first catalyst.

  In the method for forming a silica-based cured film of the present invention, it is more preferable that the composition for forming a silica-based film further contains a second catalyst. Since this second catalyst has the same action as the first catalyst described above, the composition for forming a silica-based film further contributes to lowering the dielectric constant and increasing the mechanical strength of the resulting silica-based cured film. be able to.

  In the method for forming a silica-based cured film of the present invention, it is more preferable that the second catalyst exhibits a catalytic action for a dehydration condensation reaction between silanol groups. Thereby, the dielectric constant raise of a silica type cured film can further be suppressed, and the mechanical strength can be improved further. This is considered to be due to the same factors as in the case where the dehydration condensation reaction catalyst between silanol groups is used as the first catalyst.

  In the method for forming a silica-based cured film of the present invention, the second catalyst contains one or more compounds selected from the group consisting of a second acidic compound, a second basic compound, and a second onium salt compound. It is more preferable. Here, the second acidic compound is one excluding the acidic onium salt compound, and the second basic compound is one excluding the basic onium salt compound. These catalysts have the effect of further promoting the dehydration condensation reaction between unreacted silanol groups. From the same viewpoint, in the method for forming a silica-based cured film of the present invention, it is more preferable that the second basic compound has a nitrogen atom in the molecule.

  The liquid for improving a silica-based cured film of the present invention is the liquid used in the above-described method for forming a silica-based cured film. Therefore, when this silica-based cured film improving liquid is used, it is possible to form a silica-based cured film that simultaneously satisfies a sufficiently low dielectric constant and a sufficiently high mechanical strength.

  The silica-based cured film of the present invention is provided on a substrate and is formed by the above-described method for forming a silica-based cured film. In particular, such a film is formed between conductive layers adjacent to each other among a plurality of conductive layers provided on a substrate, that is, an insulating film that needs to sufficiently reduce leakage current, For example, it is useful as an interlayer insulating film.

  The electronic component of the present invention is characterized in that the above-mentioned silica-based cured film is formed on a substrate. Such an electronic component of the present invention has sufficiently high quality and excellent reliability.

  According to the present invention, it is possible to provide a method for forming a silica-based cured film having a relative dielectric constant equal to or lower than that of a conventional porous film and sufficiently excellent in mechanical strength. The present invention also provides a silica-based cured film improving liquid used in a method for forming a silica-based cured film, a silica-based cured film obtained by the forming method, and an electronic component including the silica-based cured film. it can.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as necessary. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios. In the present specification, “(meth) acrylic acid” means “acrylic acid” and “methacrylic acid” corresponding thereto, and “(meth) acrylate” means “acrylate” and “methacrylate” corresponding thereto. means.

  In the method for forming a silica-based cured coating according to the present invention, a liquid containing the first catalyst is formed inside a silica-based coating that is a coating mainly formed of a material having a Si—O bond and formed on a substrate. The first step for permeation and the second step for curing the silica-based coating after the first step to obtain a silica-based cured coating are essential steps.

(Preparation of substrate)
Before the first step, a substrate such as a Si wafer on which a silica-based film is formed is prepared. Although it does not specifically limit as a method of forming a silica-type film on a board | substrate, For example, the following method is mentioned. First, a silica-based film forming composition containing a siloxane resin obtained from a condensable silicon-containing compound is applied on a substrate by condensation such as hydrolysis condensation to form a coating film.

The above silicon-containing compound is not particularly limited as long as it has a silicon (Si) atom in its molecule and can be condensed, but in order to obtain the effect of the present invention more effectively and reliably, for example, the above general formula It is preferable to use the one represented by (1). Here, in the formula (1), R ¹ is a group having a B atom, an N atom, an Al atom, a P atom, a Si atom, a Ge atom, or a Ti atom, an organic group having 1 to 20 carbon atoms, or an H atom or F represents an atom, and X represents a hydrolyzable group. Specific examples of the hydrolyzable group X include an alkoxy group, an aryloxy group, a halogen group, an acetoxy group, an isocyanate group, and a hydroxyl group. Among these, an alkoxy group is preferable from the viewpoints of liquid stability when a composition for forming a silica-based film is used, film coating characteristics of the composition, and the like.

  Examples of the compound represented by the general formula (1) when the hydrolyzable group X is an alkoxy group include tetraalkoxysilane, trialkoxysilane, and diorganodialkoxysilane, which may be substituted. It is done.

  Examples of the tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-iso-propoxysilane, tetra-n-butoxysilane, tetra-sec-butoxysilane, tetra-tert-butoxysilane, and the like. It can be illustrated.

  Trialkoxysilanes include trimethoxysilane, triethoxysilane, tripropoxysilane, fluorotrimethoxysilane, fluorotriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltri-n-propoxysilane, methyltri-iso-propoxy. Silane, methyltri-n-butoxysilane, methyltri-iso-butoxysilane, methyltri-tert-butoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltri-n-propoxysilane, ethyltri-iso-propoxysilane, ethyltri-n -Butoxysilane, ethyltri-iso-butoxysilane, ethyltri-tert-butoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane N-propyltri-n-propoxysilane, n-propyltri-iso-propoxysilane, n-propyltri-n-butoxysilane, n-propyltri-iso-butoxysilane, n-propyltri-tert-butoxy Silane, iso-propyltrimethoxysilane, iso-propyltriethoxysilane, iso-propyltri-n-propoxysilane, iso-propyltri-iso-propoxysilane, iso-propyltri-n-butoxysilane, iso-propyltri -Iso-butoxysilane, iso-propyltri-tert-butoxysilane, n-butyltrimethoxysilane, n-butyltriethoxysilane, n-butyltri-n-propoxysilane, n-butyltri-iso-propoxysilane, n- Butyrto -N-butoxysilane, n-butyltri-iso-butoxysilane, n-butyltri-tert-butoxysilane, n-butyltriphenoxysilane, sec-butyltrimethoxysilane, sec-butyltriethoxysilane, sec-butyltri-n -Propoxysilane, sec-butyltri-iso-propoxysilane, sec-butyltri-n-butoxysilane, sec-butyltri-iso-butoxysilane, sec-butyltri-tert-butoxysilane, t-butyltrimethoxysilane, t-butyl Triethoxysilane, t-butyltri-n-propoxysilane, t-butyltri-iso-propoxysilane, t-butyltri-n-butoxysilane, t-butyltri-iso-butoxysilane, t-butyltri-tert-butyl Toxisilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltri-n-propoxysilane, phenyltri-iso-propoxysilane, phenyltri-n-butoxysilane, phenyltri-iso-butoxysilane, phenyltri-tert-butoxy Examples include silane, trifluoromethyltrimethoxysilane, pentafluoroethyltrimethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, and 3,3,3-trifluoropropyltriethoxysilane.

  Diorganodialkoxysilanes include dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldi-n-propoxysilane, dimethyldi-iso-propoxysilane, dimethyldi-n-butoxysilane, dimethyldi-sec-butoxysilane, dimethyldi-tert-butoxy. Silane, diethyldimethoxysilane, diethyldiethoxysilane, diethyldi-n-propoxysilane, diethyldi-iso-propoxysilane, diethyldi-n-butoxysilane, diethyldi-sec-butoxysilane, diethyldi-tert-butoxysilane, di-n- Propyldimethoxysilane, di-n-propyldiethoxysilane, di-n-propyldi-n-propoxysilane, di-n-propyldi-iso-propoxysilane, di-n-pro Ludi-n-butoxysilane, di-n-propyldi-sec-butoxysilane, di-n-propyldi-tert-butoxysilane, di-iso-propyldimethoxysilane, di-iso-propyldiethoxysilane, di-iso- Propyl di-n-propoxy silane, di-iso-propyl di-iso-propoxy silane, di-iso-propyl di-n-butoxy silane, di-iso-propyl di-sec-butoxy silane, di-iso-propyl di-tert-butoxy silane Di-n-butyldimethoxysilane, di-n-butyldiethoxysilane, di-n-butyldi-n-propoxysilane, di-n-butyldi-iso-propoxysilane, di-n-butyldi-n-butoxysilane Di-n-butyldi-sec-butoxysilane, di-n Butyl di-tert-butoxysilane, di-sec-butyldimethoxysilane, di-sec-butyldiethoxysilane, di-sec-butyldi-n-propoxysilane, di-sec-butyldi-iso-propoxysilane, di-sec- Butyldi-n-butoxysilane, di-sec-butyldi-sec-butoxysilane, di-sec-butyldi-tert-butoxysilane, di-tert-butyldimethoxysilane, di-tert-butyldiethoxysilane, di-tert- Butyldi-n-propoxysilane, di-tert-butyldi-iso-propoxysilane, di-tert-butyldi-n-butoxysilane, di-tert-butyldi-sec-butoxysilane, di-tert-butyldi-tert-butoxysilane , Diphenyl dimeth Xysilane, diphenyldiethoxysilane, diphenyldi-n-propoxysilane, diphenyldi-iso-propoxysilane, diphenyldi-n-butoxysilane, diphenyldi-sec-butoxysilane, diphenyldi-tert-butoxysilane, bis (3 , 3,3-trifluoropropyl) dimethoxysilane, and diorganodialkoxysilane such as methyl (3,3,3-trifluoropropyl) dimethoxysilane.

  As the compound represented by the above general formula (1) when the hydrolyzable group X is an aryloxy group, tetraaryloxysilane, triaryloxysilane, diorganodiaryloxysilane each optionally substituted Etc. Examples of tetraaryloxysilane include tetraphenoxysilane. Examples of triaryloxysilane include methyltriphenoxysilane, ethyltriphenoxysilane, n-propyltriphenoxysilane, iso-propyltriphenoxysilane, sec-butyltriphenoxysilane, t-butyltriphenoxysilane, phenyltriphenoxysilane, etc. Is mentioned. Diorganodiaryloxysilanes include dimethyldiphenoxysilane, diethyldiphenoxysilane, di-n-propyldiphenoxysilane, di-iso-propyldiphenoxysilane, di-n-butyldiphenoxysilane, di-sec-butyl. Examples include diphenoxysilane, di-tert-butyldiphenoxysilane, diphenyldiphenoxysilane, and the like.

  As the compound (halogenated silane) represented by the general formula (1) when the hydrolyzable group X is a halogen atom (halogen group), the alkoxy group in each alkoxysilane molecule described above is substituted with a halogen atom. The compound which was made can be illustrated. Furthermore, examples of the compound (acetoxysilane) represented by the above formula (1) when X is an acetoxy group include compounds in which the alkoxy group in each alkoxysilane molecule described above is substituted with an acetoxy group. Moreover, as a compound (isocyanate silane) represented by the said Formula (1) in case X is an isocyanate group, the compound by which the alkoxy group in each above-mentioned alkoxysilane molecule was substituted by the isocyanate group is mentioned. Furthermore, examples of the compound (hydroxysilane) represented by the above formula (1) when X is a hydroxyl group include compounds in which the alkoxy group in each alkoxysilane molecule described above is substituted with a hydroxyl group. In addition, the compound represented by the said Formula (1) can be used individually by 1 type or in combination of 2 or more types.

  Among these compounds, tetraalkoxysilane and organotrialkoxysilane are more preferable, and tetraethoxysilane and methyltriethoxysilane are particularly preferable from the viewpoints of liquid stability of the composition itself, coating coating characteristics, and the like.

In the compound represented by the general formula (1), n represents an integer of 0 to 2. However, when n is 2, each R ¹ may be the same or different. Further, when n is 0 to 2, the above Xs may be the same or different. In addition, it is preferable that n is 0-1, and the compound represented by the general formula (1) in which n is 0 and the compound represented by the general formula (1) in which n is 1 are used in combination. It is preferable to do. When a compound in which n is 0 and 1 is combined, the siloxane resin includes a unit represented by SiO ₂ and a unit represented by R ¹ SiO _1.5 . Here, R ¹ has the same meaning as described above. Such a siloxane resin is obtained by cohydrolyzing and condensing the above-mentioned tetraalkoxysilane and trialkoxysilane having polyfunctionality. The unit represented by SiO ₂ is a unit derived from tetraalkoxysilane, and the unit represented by R ¹ SiO _1.5 is a unit derived from trialkoxysilane. Since the siloxane resin contains such a unit, the crosslink density is improved, so that the film characteristics can be improved.

From the viewpoint of lowering the dielectric constant and increasing the mechanical strength of the finally obtained silica-based cured coating, it is preferable that the composition for forming a silica-based coating contains a catalyst (second catalyst). More preferably, it exhibits a catalytic action for the dehydration condensation reaction between silanol groups as represented by the formula (A).

  Such a catalyst acts as a catalyst (second catalyst) for promoting the hydrolysis-condensation reaction in the hydrolysis-condensation of the compound represented by the above formula (1). As such a catalyst, an acidic compound (second acidic compound), a basic compound (second basic compound), or an onium salt compound (second onium salt compound) can be used. Among these, it is preferable to use the second acidic compound as the one that promotes the hydrolytic condensation before applying the silica-based film forming composition onto the substrate.

  The second acidic compound may be either an inorganic acid or an organic acid, and may be used alone or in combination of two or more.

  As the inorganic acid, hydrochloric acid, phosphoric acid, nitric acid, boric acid, sulfuric acid, hydrofluoric acid and the like can be used. Among these, nitric acid is preferable from the viewpoints of improving the hardness of the silica-based cured film that is the finally obtained cured film and the stability of the coating solution.

  Organic acids include acetic acid, maleic acid, oxalic acid, malic acid, malonic acid, fumaric acid, terephthalic acid, isophthalic acid, picolinic acid, pimelic acid, 1,10-phenanthrophosphoric acid, nicotinic acid, tartaric acid, succinic acid, glutar Acid, 2-glycerin phosphate, D-glucose-1-phosphate, adipic acid, formic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, sebacic acid, butyric acid Oleic acid, stearic acid, linoleic acid, linoleic acid, salicylic acid, benzoic acid, p-aminobenzoic acid, p-toluenesulfonic acid, phthalic acid, sulfonic acid, trifluoromethanesulfonic acid and the like can be used. Among these, maleic acid is preferable from the viewpoints of improving the hardness of the silica-based cured film that is the finally obtained cured film, further reducing the stability of the coating solution and the dielectric constant.

  The amount of the second acidic compound used as the catalyst is preferably in the range of 0.0001 mol to 1 mol with respect to 1 mol of the compound represented by the formula (1). When the amount used exceeds 1 mol, gelation tends to be promoted at the time of hydrolysis condensation, and when it is less than 0.0001 mol, the reaction (hydrolysis condensation reaction) tends not to proceed substantially.

  The second basic compound may be either an inorganic base or an organic base, and may be used alone or in combination of two or more.

  Examples of the inorganic base include sodium hydroxide and potassium hydroxide. Examples of the organic base include organic bases having a nitrogen atom in the molecule, such as ammonia, methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, N, N-dimethylamine, N, N-diethylamine, N , N-dipropylamine, N, N-dibutylamine, triethylamine, tripropylamine, tributylamine, methoxypropylamine, tetramethylethylenediamine, tetraethylethylenediamine, ethylaminopropylamine, aniline, dimethylaniline, pyridine, methylpyridine, pyrrole Piperazine, dimethylpiperazine, pyrrolidine, diaminobenzene, tetramethylammonium oxide, tetrabutylammonium oxide, hexamethylphosphoramide, 1.8-diaza Cyclo [5.4.0] undec-7-ene, etc. 1,5-diazabicyclo [4.3.0] non-5-ene can be exemplified.

  Among these, an organic base which is a base having no alkali metal or alkaline earth metal is preferable from the viewpoint of electrical reliability and the like. Furthermore, from the viewpoint of further promoting the dehydration condensation reaction between unreacted silanol groups, organic chlorine having a nitrogen atom in the molecule is more preferable.

  The second basic compound has an effect of promoting the dehydration condensation reaction after the composition for forming a silica-based film is applied on the substrate.

  Examples of the second onium salt compound include ammonium salts, phosphonium salts, arsonium salts, stibonium salts, oxonium salts, sulfonium salts, selenonium salts, stannonium salts, iodonium salts, and the like. In these, an ammonium salt is preferable at the point which is more excellent in stability of a composition. Examples of ammonium salts include ammonium halides and organic acid ammonium salts. The ammonium halide may be a quaternary ammonium halide salt, and examples thereof include tetramethylammonium fluoride and tetrabutylammonium fluoride.

  The organic acid ammonium salt is preferably a quaternary organic acid ammonium salt from the viewpoint of improving the stability of the solution and the electrical characteristics, and includes an organic acid salt of tetramethylammonium. Examples of the organic acid salt of tetramethylammonium include tetramethylammonium nitrate, tetramethylammonium acetate, tetramethylammonium propionate, tetramethylammonium maleate, and tetramethylammonium sulfate.

  Among these onium salt compounds, tetramethylammonium nitrate, tetramethylammonium acetate, tetramethylammonium propionate, tetramethylammonium maleate, tetramethylammonium are used to improve the electrical properties of the silica-based cured coating. Sulfate is preferred, and tetramethylammonium nitrate is more preferred.

  When an onium salt is used as an aqueous solution, the pH is preferably 1.5 to 10, more preferably 2 to 8, and particularly preferably 3 to 6. When this pH is less than 1.5 or when the pH exceeds 10, the stability of the composition for forming a silica-based film and the film formability of the resulting silica-based cured film tend to be inferior.

  The second onium salt compound is considered to have an effect of promoting the dehydration condensation reaction after coating the composition for forming a silica-based film on the substrate, but may act as a catalyst before coating. . When using an onium salt compound as the catalyst, the amount used is preferably in the range of 0.001 mass ppm to 5 mass%, based on the total amount of the silica-based film-forming composition, and is 0.01 mass ppm to 2 mass%. More preferably, it is more preferably 0.1 ppm by mass to 1% by mass. If the amount used is less than 0.001 mass ppm, the finally obtained silica-based cured film tends to have poor electrical and mechanical properties. On the other hand, when the amount used exceeds 5% by mass, the stability of the composition, the film formability and the like tend to be inferior, and the electrical characteristics and process suitability of the silica-based cured film tend to be lowered. In addition, these onium salts can be added to a desired concentration after being dissolved or diluted in water or a solvent as necessary.

  When the above-mentioned second acidic compound, second basic compound and / or second onium salt compound is used as a catalyst for the dehydration condensation reaction after applying the silica-based film forming composition on the substrate, The amount used is preferably 1 mass ppb to 3 mass%, more preferably 10 mass ppb to 1 mass%, more preferably 100 mass ppb to 0.5 mass%, based on the total amount of the composition for forming a silica-based film. Is more preferable. When the amount used is less than 1 mass ppb, the electrical properties and mechanical properties of the finally obtained silica-based cured coating tend to be lowered. On the other hand, if the amount used exceeds 3% by mass, the stability of the composition for forming a silica-based film, the film formability of the silica-based film (or silica-based cured film), etc. tend to be reduced. There is a tendency for the electrical properties and process compatibility of the to decrease.

  These catalysts can be added to the silica-based film-forming composition so as to be dissolved or diluted with water or a solvent as necessary to obtain a desired concentration.

  In this hydrolysis condensation reaction (dehydration condensation reaction), alcohol by-produced by hydrolysis may be removed using an evaporator or the like, if necessary. In addition, the amount of water present in the hydrolysis condensation reaction system can be appropriately determined. The amount of this water is 0.5 to 20 mol with respect to 1 mol of the compound represented by the formula (1). A value within the molar range is preferred. When the amount of water is less than 0.5 mol or more than 20 mol, the film formability of the silica-based cured film is deteriorated and the storage stability of the composition itself tends to be lowered.

  The obtained siloxane resin is measured by gel permeation chromatography (hereinafter referred to as “GPC”) and converted using a standard polystyrene calibration curve from the viewpoint of solubility in a solvent, mechanical properties, moldability, and the like. The weight average molecular weight is preferably 300 to 20,000, and more preferably 500 to 10,000. When the weight average molecular weight is less than 300, the film formability of the silica-based film tends to be inferior. On the other hand, when the weight average molecular weight exceeds 20000, the compatibility with the solvent tends to decrease.

  The carbon content in the siloxane resin is preferably 11% by mass or less, more preferably 10.4% by mass or less, and even more preferably 9.6% by mass or less based on the total mass of the siloxane resin. .8% by mass or less is particularly preferable. If the carbon content exceeds 11% by mass, the adhesion to the upper layer film, the mechanical strength of the interlayer insulating film, etc. tend to be remarkably inferior. Further, the carbon content is preferably about 6% by mass or more. If it is less than about 6% by mass, the electrical properties of the interlayer insulating film tend to be inferior.

This carbon content ratio is calculated on the assumption that the siloxane resin skeleton is completely condensed and cured. Here, a case where the siloxane resin is a copolymer of tetraalkoxysilane which is a compound not containing carbon and methyltrialkoxysilane which is a compound containing carbon will be described as an example. In this case, the condensation cured product of tetraalkoxysilane is assumed to be SiO ₂ (molecular weight 60.08), and the condensation cured product of methyltrialkoxysilane is assumed to be CH ₃ SiO _1.5 (molecular weight 67.12). Further, the molar ratio of SiO _{2 and} the molar ratio of CH ₃ SiO _{1.5 in} the copolymer are respectively multiplied by the molecular weight of SiO _{2 and} the molecular weight of CH ₃ SiO _1.5 , and further multiplied by each other. Using the sum as the denominator, the product of the atomic weight of carbon (12.011) and the molar ratio of CH ₃ SiO _1.5 can be calculated as the numerator. This is expressed by the following equation (3).
_{R C = Aw C × Mr CS} × 100 / {Mw S × Mr S + Mw CS × Mr CS} ... (3)

Here, in the formula (3), R _C is the carbon content (mass%), Aw _C is the atomic weight of carbon, Mw _S is the molecular weight of the condensed compound of tetraalkoxysilane, and Mw _CS is the condensed cured product of methyltrialkoxysilane. , Mr _S represents the molar ratio of tetraalkoxysilane (monomer) in the siloxane resin, and Mr _CS represents the molar ratio of methyltrialkoxysilane (monomer) in the siloxane resin.

Accordingly, when the siloxane resin is a copolymer of 0.600 mol of tetraethoxysilane and 0.400 mol of methyltriethoxysilane, the carbon content in the siloxane resin is calculated as in the following formula (4). .
R _C = 12.011 × 0.400 × 100 / (60.08 × 0.600 + 67.12 × 0.400) = 7.64 <unit: mass%> (4)

  In the composition for forming a silica-based film, a solvent capable of dissolving the compound represented by the general formula (1) may be contained. Examples of such solvents include ether acetate solvents, ether glycol solvents, alcohol solvents, ketone solvents, ether solvents other than those mentioned above, ester solvents, acetonitrile, N, N-dimethylformamide, N, N. -Solvents such as dimethylacetamide, N, N-dimethylsulfoxide, water and the like can be mentioned, and these can be used alone or in combination of two or more.

  As ether acetate solvents, ethylene glycol methyl ether propionate, ethylene glycol ethyl ether propionate, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, diethylene glycol methyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol-n-butyl ether Examples include acetate, propylene glycol ethyl ether acetate, propylene glycol propyl ether acetate, dipropylene glycol methyl ether acetate, dipropylene glycol ethyl ether acetate and the like.

  Examples of ether glycol solvents include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-hexyl ether, ethylene glycol monophenyl ether, ethylene glycol mono-2-ethylbutyl ether, propylene glycol monomethyl ether, propylene glycol mono Examples include ethyl ether, propylene glycol monopropyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-n-hexyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol monoethyl ether.

  Examples of alcohol solvents include methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, sec-butanol, t-butanol, n-pentanol, i-pentanol, 2-methylbutanol, sec -Pentanol, t-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2-ethylbutanol, sec-heptanol, n-octanol, 2-ethylhexanol, sec-octanol, n-nonyl alcohol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl alcohol, phenol, cyclohexanol, methylcyclohexanol, Down benzyl alcohol, ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol and the like can be exemplified.

  Examples of ketone solvents include acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone, methyl-i-butyl ketone, methyl-n-pentyl ketone, methyl-n-hexyl ketone, diethyl ketone, and di-i-. Examples include butyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonyl acetone, diacetone alcohol, acetophenone, and γ-butyrolactone.

  As ether solvents, ethyl ether, i-propyl ether, n-butyl ether, n-hexyl ether, 2-ethylhexyl ether, ethylene oxide, 1,2-propylene oxide, dioxolane, 4-methyldioxolane, dioxane, dimethyldioxane, ethylene Examples include glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, ethoxytriglycol, tetraethylene glycol di-n-butyl ether, tripropylene glycol monomethyl ether, tetrahydrofuran, and 2-methyltetrahydrofuran.

  Examples of ester solvents include methyl acetate, ethyl acetate, n-propyl acetate, i-propyl acetate, n-butyl acetate, i-butyl acetate, sec-butyl acetate, n-pentyl acetate, sec-pentyl acetate, and 3-acetate acetate. Methoxybutyl, methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, benzyl acetate, cyclohexyl acetate, methyl cyclohexyl acetate, nonyl acetate, γ-butyrolactone, γ-valerolactone, methyl acetoacetate, ethyl acetoacetate, glycol diacetate Methoxytriglycol acetate, ethyl propionate, n-butyl propionate, i-amyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, ethyl lactate, n-butyl lactate, n-amyl lactate, etc. Is mentioned.

  The amount of the solvent used may be such that the amount of the siloxane resin in the composition for forming a silica-based film is 3% by mass to 25% by mass with respect to the total amount of the composition for forming a silica-based film. preferable. With respect to the amount of this solvent, when the amount of the siloxane resin in the composition for forming a silica-based film is less than 3% by mass, the liquid stability of the composition for forming a silica-based film and the formation of a silica-based film (or a silica-based cured film) are achieved. There exists a tendency for film property etc. to fall. When the amount of the siloxane resin in the composition for forming a silica-based film exceeds 25% by mass, it tends to be difficult to obtain a silica-based cured film having a desired film thickness.

  The composition for forming a silica-based film is decomposed by heat treatment at 500 ° C. or less, preferably 250 to 500 ° C., plasma treatment, or ultraviolet ray, infrared ray, or electron beam irradiation to form voids (holes). You may contain a decomposable compound and a porous body as needed.

  Examples of such compounds include vinyl ether compounds, vinyl compounds having oxyethylene units, vinyl compounds having oxypropylene units, vinyl pyridine compounds, styrene compounds, alkyl ester vinyl compounds, and (meth) acrylic compounds. Examples thereof include those selected from acids or (meth) acrylate compounds, polymers having an oxyalkylene unit, polycarbonate polymers and the like.

  Among these, the polymer which has an oxyalkylene unit from a viewpoint of the decomposition characteristic and the mechanical strength of a silica type cured film is preferable.

  Examples of the oxyalkylene unit include an oxyethylene unit, an oxypropylene unit, an oxytetramethylene unit, and an oxybutylene unit. Polymers having oxyalkylene units include polyoxyethylene alkyl ether, polyoxyethylene sterol ether, polyoxyethylene lanolin derivative, ethylene oxide derivative of alkylphenol formalin condensate, polyoxyethylene polyoxypropylene block copolymer, polyoxypropylene alkyl Ether type compounds such as ether, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene glycerin fatty acid ester, polyoxyethylene sorbitol fatty acid ester, ether ester type compound such as polyoxyethylene fatty acid alkanolamide sulfate, polyethylene glycol fatty acid ester, Ethylene glycol fatty acid ester, fatty acid monoglyceride, polyglycerin fatty acid ester Le, sorbitan fatty acid ester, ether-ester type compounds such as propylene glycol fatty acid esters, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and polyethylene glycol, glycol-type compounds such as polypropylene glycol. In these, the polymer which has an oxypropylene unit from a viewpoint of the decomposition characteristic and the mechanical strength of a silica type cured film is preferable, and a polypropylene glycol is still more preferable.

  Examples of the (meth) acrylic acid or (meth) acrylate compound include acrylic acid alkyl ester, methacrylic acid alkyl ester, acrylic acid alkoxyalkyl ester, methacrylic acid alkyl ester, and methacrylic acid alkoxyalkyl ester. Examples of the alkyl acrylate ester include 1 to 6 carbon atoms such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, pentyl acrylate, and hexyl acrylate. Examples of the alkyl ester and alkyl methacrylate ester include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, pentyl methacrylate, hexyl methacrylate and the like. ~ 6 alkyl esters, acrylic acid alkoxyalkyl esters as methoxymethyl acrylate, ethoxyethyl acrylate, methacrylic acid alkoxyalkyl esters as methoxymethyl methacrylate Methacrylate ethoxyethyl or the like can be exemplified.

  The (meth) acrylic acid or (meth) acrylate compound may be used as a copolymer with a compound having a hydroxyl group. Specific examples thereof include 2-hydroxyethyl acrylate, diethylene glycol acrylate, 2-hydroxypropyl acrylate, dipropylene glycol acrylate, methacrylic acid, 2-hydroxyethyl methacrylate, diethylene glycol methacrylate, 2-hydroxypropyl methacrylate, and dipropylene glycol methacrylate. Can be mentioned.

  Examples of the polycarbonate include polycondensates of carbonic acid and alkylene glycol such as polyethylene carbonate, polypropylene carbonate, polytrimethylene carbonate, polytetramethylene carbonate, polypentamethylene carbonate, and polyhexamethylene carbonate.

  The decomposable compound is measured by GPC from the viewpoints of solubility in the above-mentioned solvent, compatibility with the siloxane resin, mechanical properties of the silica-based cured coating, moldability of the silica-based coating and the silica-based cured coating, and the like. The weight average molecular weight converted using a standard polystyrene calibration curve is preferably 200 to 10000, more preferably 300 to 5000, and still more preferably 400 to 2000. When the weight average molecular weight is less than 200, the formation of pores tends to be insufficient. On the other hand, when the weight average molecular weight exceeds 10,000, the compatibility with the siloxane resin tends to decrease.

  The content of the decomposable compound is preferably 0.10% by mass to 10% by mass, and 1.0% by mass to 5.0% by mass based on the total mass of the composition for forming a silica-based film. Is more preferable. When this content is less than 0.10% by mass, the formation of pores tends to be insufficient. On the other hand, if it exceeds 10% by mass, the film strength tends to decrease.

  It is desirable that the composition for forming a silica-based film does not contain an alkali metal and an alkaline earth metal. When these metals are contained, the content thereof is preferably 100 mass ppb or less and more preferably 20 mass ppb or less with respect to the mass of the entire composition. If the content of these metals exceeds 100 mass ppb, metal ions tend to flow into the semiconductor element, and it tends to be difficult to obtain desired device characteristics. Therefore, it is preferable to remove these alkali metals and alkaline earth metals by using an ion exchange filter or the like as necessary when preparing the composition for forming a silica-based film.

  The composition for forming a silica-based film may contain a surfactant as necessary to prevent aggregation of the decomposable compound or the porous body and to improve dispersibility.

  As the surfactant, a nonionic surfactant, a cationic surfactant, and an anionic surfactant can be used. Among these, a nonionic surfactant is preferable from the viewpoint of hardly containing a halogen component and a metal impurity.

  Examples of the nonionic surfactant include a compound having an ethylene oxide structure, a compound having a propylene glycol structure, and a compound having an acetylene glycol structure.

  As the surfactant, a triblock copolymer having three polyalkylene oxide chains can also be used.

  These surfactants may be used individually by 1 type, and may be used in combination of 2 or more type.

  The method for applying the silica-based film-forming composition on the substrate is not particularly limited, such as spin coating, spray coating, dip coating, flow coating, roll coating, slit coating, screen printing, etc. The spin coating method is preferable from the viewpoint of excellent film formability and film uniformity. Hereinafter, a method for forming a silica-based film will be described by taking this spin coating method as an example.

  First, a coating film is formed by spin-coating a composition for forming a silica-based film on a substrate such as a Si wafer, preferably at 300 to 5000 revolutions / minute, more preferably at 700 to 3000 revolutions / minute. To do. At this time, if the rotational speed is less than 300 revolutions / minute, the film uniformity tends to be lowered. On the other hand, if it exceeds 5000 revolutions / minute, the film formability may be deteriorated.

  Next, a heating step is performed on the coating film to obtain a silica-based film. This step is a step for drying the solvent in the composition and increasing the degree of cure of the siloxane resin, and heat treatment is performed using a hot plate or the like at a temperature of 50 to 400 ° C., preferably 100 to 350 ° C. . The heating step may be multi-stage heating at different temperatures as necessary.

  When this heating temperature is less than 50 ° C., the solvent tends not to be sufficiently dried. On the other hand, when the heating temperature exceeds 400 ° C., the decomposable compound is thermally decomposed and volatilized before the siloxane skeleton is formed in the coating, making it difficult to obtain a silica-based cured coating having desired mechanical strength and low dielectric properties. There is a fear.

(First step)
Next, a silica-based cured film improving liquid (hereinafter referred to as “film improving liquid”), which is a liquid containing the first catalyst, is infiltrated into the silica-based film formed on the substrate. The liquid for improving the film is not particularly limited as long as it contains the first catalyst and has a surface tension smaller than the surface tension of the silica-based film through which the first catalyst is permeated. If the surface tension of the coating film improving liquid is smaller than the surface tension of the silica coating film, the permeability of the coating film improving liquid into the silica coating film is improved, so that the dielectric constant of the resulting silica coating film is sufficiently reduced. In addition, the mechanical strength is sufficiently improved.

  From the same viewpoint, the difference between the surface tension of the silica-based coating and the surface tension of the coating-improving liquid is more preferably 5 mN / m or more, further preferably 5 mN / m to 15 mN / m, and more preferably 10 mN / m. It is especially preferable that it is m-15mN / m. When this difference exceeds 15 mN / m, the silica-based film tends to swell and the film thickness tends to be non-uniform.

  The surface tension of the film-improving liquid is preferably 21 mN / m or less, more preferably 8 mN / m to 21 mN / m, and more preferably 9 mN / m to 15 mN / nm from the viewpoint of permeability to the silica-based film. And more preferably 9 mN / m to 13 mN / m. When the surface tension of the film-improving liquid is less than 8 mN / m, it tends to be difficult to prepare the film-improving liquid.

  The surface tension of the film-improving liquid can be measured by a surface tension measuring device using a known method such as the Wilhelmy plate method or the ring (Dunui) method. In the present invention, the surface tension is measured by the ring method.

  The surface tension of the silica-based coating is derived as so-called critical surface tension. The method for deriving the critical surface tension is as follows. First, on the solid surface from which the critical surface tension is to be derived, that is, in the present invention, on the surface of the silica-based film, several kinds of known and different surface tensions (temperature 23 to 25 ° C., relative humidity 40 to 60%, under the ring method) ) Is dropped to form droplets on the solid surface. Next, the contact angle (θ) of each droplet on the solid surface is measured. The value of cos θ is obtained from the obtained contact angle (θ), and the value of cos θ (vertical axis, y axis) against the surface tension (horizontal axis, x axis) of the liquid is plotted on a graph. From the plot, the relationship between the surface tension (x) and cos θ (y) is obtained by approximating it to a linear expression. Then, cos θ = 1 is inserted into the obtained linear expression, and the surface tension at that time, that is, the critical surface tension is derived.

  Critical surface tension is a measure of the wetting characteristics of a solid surface, and when a liquid having a surface tension smaller than the critical surface tension is dropped onto the solid surface, the liquid spontaneously spreads on the solid surface, and the solid Wet the surface completely. A solid surface with a high critical surface tension is easily wetted by a relatively large number of liquids, and a solid surface with a small critical surface tension is not easily wetted by a relatively large number of liquids. Ed., 2nd edition, pages 20-49).

Here, the contact angle (θ) of the droplet is measured with a commercially available contact angle measuring machine under measurement conditions of 23 to 25 ° C., normal pressure (1 atm), and normal humidity (40 to 60% as relative humidity). be able to. When the relationship between the surface tension (x) and cos θ (y) is approximated by a linear expression, a straight line is obtained from the plot by the least square method, and the slope and intercept of the straight line are derived. The linear expression thus obtained is expressed as, for example, the following expression (5).
x = (y−b) / a <unit; dyn / cm, mN / m> (5)
In the formula, x is the surface tension of the liquid (unit: dyn / cm), y is cos θ, a is the slope of the straight line, and b is the intercept of the straight line. The value of x when y = 1 in this equation (5) is the critical surface tension.

  Some known and different surface tension liquids used in deriving the critical surface tension include hydrogen bonding liquids such as water, glycerin, formamide, ethylene glycol, propylene glycol, isopropyl alcohol, n-hexane, n -Hydrocarbon liquids such as decane.

  From the viewpoint of reducing the compound having a silanol group remaining in the silica-based film, the first catalyst preferably has a catalytic action on a dehydration condensation reaction between silanol groups. As such a catalyst, an acidic compound (first acidic compound), a basic compound (first basic compound), or an onium salt compound (first onium salt compound) can be used.

  Examples of the first acidic compound include inorganic acids such as hydrochloric acid, phosphoric acid, nitric acid, boric acid, sulfuric acid, and hydrofluoric acid, acetic acid, maleic acid, oxalic acid, malic acid, malonic acid, fumaric acid, terephthalic acid, and isophthalic acid. Acid, picolinic acid, pimelic acid, 1,10-phenanthrophosphoric acid, nicotinic acid, tartaric acid, succinic acid, glutaric acid, 2-glycerin phosphoric acid, D-glucose-1-phosphate, adipic acid, formic acid, propionic acid, butane Acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, sebacic acid, butyric acid, oleic acid, stearic acid, linoleic acid, linolenic acid, salicylic acid, benzoic acid, p-aminobenzoic acid, p- Organic acids such as toluenesulfonic acid, phthalic acid, sulfonic acid, and trifluoromethanesulfonic acid can be used.

  Examples of the first basic compound include inorganic bases such as sodium hydroxide and potassium hydroxide, and organic bases such as ammonia and triethylamine, and one of these may be used alone or in combination of two or more. Good.

  Examples of the organic base include organic bases having a nitrogen atom in the molecule, such as methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, N, N-dimethylamine, N, N-diethylamine, N, N-dipropylamine, N, N-dibutylamine, triethylamine, tripropylamine, tributylamine, methoxypropylamine, tetramethylethylenediamine, tetraethylethylenediamine, ethylaminopropylamine, aniline, dimethylaniline, pyridine, methylpyridine, Pyrrole, piperazine, dimethylpiperazine, pyrrolidine, diaminobenzene, tetramethylammonium oxide, tetrabutylammonium oxide, hexamethylphosphoramide, 1.8-dia Bicyclo [5.4.0] undec-7-ene, 1,5-diazabicyclo [4.3.0] compounds such as non-5-ene.

  Among these, an organic base which is a base having no alkali metal or alkaline earth metal is preferable from the viewpoint of electrical reliability and the like. Furthermore, from the viewpoint of further promoting the dehydration condensation reaction between unreacted silanol groups, an organic base having a nitrogen atom in the molecule is more preferable.

  Examples of the first onium salt compound include ammonium salt, phosphonium salt, arsonium salt, stibonium salt, oxonium salt, sulfonium salt, selenonium salt, stannonium salt, iodonium salt and the like. In these, an ammonium salt is preferable from a viewpoint which is more excellent by stability of a composition. Examples of ammonium salts include ammonium halides and organic acid ammonium salts. The ammonium halide may be a quaternary ammonium halide salt, and examples thereof include tetramethylammonium fluoride and tetrabutylammonium fluoride.

  The organic acid ammonium salt is preferably a quaternary organic acid ammonium salt from the viewpoint of solution stability and electrical characteristics, and examples thereof include an organic acid salt of tetramethylammonium. Examples of the organic acid salt of tetramethylammonium include tetramethylammonium nitrate, tetramethylammonium acetate, tetramethylammonium propionate, tetramethylammonium maleate, and tetramethylammonium sulfate.

  Among these onium salt compounds, tetramethylammonium nitrate, tetramethylammonium acetate, tetramethylammonium propionate, tetramethylammonium maleate, tetramethylammonium are used to improve the electrical properties of the silica-based cured coating. Sulfate is more preferred, and tetramethylammonium nitrate is particularly preferred.

  When the above-mentioned first acidic compound, first basic compound and / or first onium salt compound are used as the first catalyst, the amount used is 0.0010 based on the total amount of the film-improving liquid. The content is preferably 10% by mass to 10% by mass, more preferably 0.010% by mass to 5.0% by mass, and still more preferably 0.05% by mass to 2.0% by mass. If the amount used is less than 0.0010% by mass, the electrical properties and mechanical properties of the finally obtained silica-based cured film tend to be lowered. Moreover, when the usage-amount exceeds 10 mass%, it exists in the tendency for the electrical property and process compatibility of a silica type cured film to fall.

  The film improving liquid is preferably a solution containing a solvent. When the film-improving liquid contains a solvent, the dispersibility of the first catalyst in the film-improving liquid is improved, so that it is possible to introduce the first catalyst together with the liquid into the silica-based film. Become. This leads to suppression of increase in dielectric constant and improvement of mechanical strength of the finally obtained silica-based cured film.

  Examples of the solvent contained in the film improving liquid include saturated hydrocarbon solvents such as butane and pentane, ether solvents such as diethyl ether and isopropyl ether, perfluorodecalin, perfluorocyclohexane, perfluorohexane, and perfluoro. Fluorine-containing aliphatic hydrocarbon solvents such as octane, 1H, 1H, 1H, 2H, 2H-perfluorooctane, 1H, 1H, 1H, 2H, 2H-perfluorodecane, perfluorotripentylamine, perfluorotributylamine , Fluorine-containing alkylamine solvents such as perfluorotripropylamine, fluorine-containing cyclic ether solvents such as perfluoro (2-butyltetrahydrofuran), and hydrocarbons such as methylperfluorobutylether and methylperfluorohexylether. Oroeteru solvents and the like.

  Among these, a solvent having a fluorine atom in the molecule such as a fluorine-containing aliphatic hydrocarbon solvent, a fluorine-containing alkylamine solvent, a fluorine-containing cyclic ether solvent, or a hydrofluoroether solvent is preferable. The film-improving liquid containing such a solvent tends to have a low surface tension, and thereby has a higher permeability to the silica-based film. The above-mentioned solvents may be used alone or in combination of two or more.

  As a method of infiltrating the coating film-improving liquid into the silica-based film, a method of applying the film-improving liquid to the silica-based film (spin coating method, flow coating method, roll coating method, slit coating method, screen printing method, etc.) Examples thereof include a method of immersing a silica-based film in a liquid for improving a film (dip coating method) and a method of spraying a liquid for improving a film on a silica-based film (spray coating method). Among these, the spin coating method is preferable from the viewpoint of further improving the permeability into the silica-based coating and allowing the coating-improving liquid to uniformly penetrate the entire silica-based coating. Thereby, the film formability and film uniformity of the silica-based cured coating obtained are improved.

  When the spin coating method is adopted as the method for penetrating the liquid for improving the film, the spin speed at the time of coating is preferably 100 rpm / min to 5000 rpm, and more preferably 500 rpm / min to 2000 rpm. preferable. When the spin speed is less than 100 revolutions / minute, the film uniformity of the film-improving liquid decreases, whereas when it exceeds 5000 revolutions / minute, the film-forming property of the film-improving liquid tends to be degraded.

  When both the formation of the silica-based coating and the penetration of the coating-improving liquid are performed by a spin coating method, the spin speed when applying the coating-improving liquid is higher than the spin speed when forming the silica-based coating. They may be low and their spin speeds may be the same. In this case, it is possible to form the film more efficiently while sufficiently satisfying both the film uniformity and film formability, and when the silica-based film has pores, the coating-improving liquid penetrates into the pores. It becomes possible to make it easier.

(Second step)
In the second step after the first step, the silica-based coating in a state where the coating-improving liquid has permeated therein is cured to obtain a silica-based cured coating. The curing treatment of the silica-based film is preferably performed as follows.

First, in order to mainly remove volatile components such as a solvent, the silica-based coating is heated at a temperature of 50 to 400 ° C. using a known heat treatment apparatus such as a hot plate. During this heat treatment, the atmosphere around the silica-based coating is not particularly limited, and may be any of an inert gas atmosphere such as N ₂ , He and Ar, an oxidizing gas atmosphere such as O ₂ and air, or a reducing gas atmosphere. There may be. The heating time may be such that volatile components such as a solvent can be removed, and varies depending on the heating temperature and atmosphere, but is usually about 10 seconds to 60 seconds.

Next, in order to finally cure the silica-based film finally, the silica-based film is heated at a temperature of 150 to 500 ° C. using a known heat treatment apparatus such as a quartz tube furnace. If this temperature is less than 150 ° C., the silica-based coating tends to be insufficiently cured, and if it exceeds 500 ° C., there is a high possibility that the amount of heat input increases and the wiring metal deteriorates when there is a metal wiring layer. Tend to be. At the time of this heat treatment, the atmosphere around the silica-based film is not particularly limited, but from the viewpoints of suppressing the deterioration of the silica-based film and improving the electrical characteristics, it is performed in an inert gas atmosphere such as N ₂ , Ar, and He. Is preferred. When O ₂ is contained in the atmosphere, the O ₂ concentration is preferably 10 volume ppm to 5000 volume ppm in order to suppress deterioration of the silica-based film. The heating time is preferably 2 minutes to 60 minutes. If the heating time is less than 2 minutes, curing of the silica-based film tends to be insufficient, and if it exceeds 60 minutes, the amount of heat input may increase when there is a metal wiring layer, which may cause deterioration of the wiring metal. It tends to be higher.

  As a heat treatment apparatus in these heat treatments, a rapid thermal annealing (RTA) furnace is preferable in addition to a hot plate and a quartz tube furnace. In addition, a microwave treatment, a UV treatment, an EB (electron beam) treatment, or the like may be used in combination as a heat treatment or a hardening treatment between the formation treatment of the silica-based film and the above-described final hardening treatment.

  Note that the above heat treatment is performed in two stages of different temperatures, different atmospheres, or different heat treatment apparatuses, but even if the volatile matter is removed and the silica-based coating is cured by one stage of heat treatment. The heat treatment may be divided into three or more stages.

  The thickness of the silica-based cured film thus obtained is preferably 0.010 μm to 40 μm, and more preferably 0.050 μm to 2.0 μm. If this film thickness exceeds 40 μm, cracks are likely to occur due to stress, while if it is less than 0.010 μm, when metal wiring layers exist above and below the silica-based coating, the leakage characteristics between the upper and lower wirings are reduced. It tends to get worse.

  The silica-based cured film according to the present embodiment achieves a sufficiently low dielectric constant, and even if it has pores, its mechanical strength is sufficiently high. This is considered to suppress an increase in dielectric constant and a decrease in mechanical strength due to the raw material remaining in the silica-based film. In other words, it is presumed that such a raw material substance can be reacted by the action of the first catalyst contained in the coating film improving liquid to be converted or removed into another substance.

  Examples of the electronic component of the present invention having such a silica-based cured coating include devices having an insulating film such as a semiconductor element and a multilayer wiring board. Specifically, in a semiconductor element, it can be used as a surface protective film (passivation film), a buffer coat film, an interlayer insulating film, and the like. On the other hand, in a multilayer wiring board, it can be suitably used as an interlayer insulating film.

  More specifically, as semiconductor elements, individual semiconductors such as diodes, transistors, capacitors, compound semiconductors, thermistors, varistors, thyristors, DRAMs (Dynamic Random Access Memory), SRAMs (Static Random Access Memory) , EPROM (Erasable Programmable Read Only Memory), Mask ROM (Mask Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), Flash Memory and other Memory Elements, Microprocessor , DSP, ASIC and other theoretical circuit elements, MMIC (monolithic microwave integrated circuit) and other integrated circuit elements such as compound semiconductors, hybrid integrated circuits (hybrids) C), light emitting diodes, such as a photoelectric conversion element such as a charge coupled device and the like. Examples of the multilayer wiring board include a high-density wiring board such as MCM. Furthermore, it can also be used as an antireflection film for a liquid crystal panel, a reflection film or a light guide film, a light guide, an antireflection film for a solar cell panel, and the like.

  FIG. 1 is a schematic cross-sectional view showing an embodiment of an electronic component according to the present invention. A memory capacitor cell 8 (electronic component) includes a gate electrode 3 (word line) provided on a silicon (Si) wafer 1 (substrate) on which diffusion regions 1A and 1B are formed via a gate insulating film 2B made of an oxide film. And interlayer insulating films 5 and 7 (insulating films) having a two-layer structure are formed between the upper electrode and the counter electrode 8C provided thereabove. Side wall oxide films 4A and 4B are formed on the side wall of the gate electrode 3, and a field oxide film 2A is formed in the diffusion region 1B on the side of the gate electrode to separate the elements.

  The interlayer insulating film 5 is deposited on the gate electrode 3 and the field oxide film 2A, and is made of the silica-based cured film according to the present invention. Near the gate electrode 3 in the interlayer insulating film 5, a contact hole 5A in which an electrode 6 functioning as a bit line is embedded is formed. Further, a flattened interlayer insulating film 7 is deposited on the flattened interlayer insulating film 5, and a storage electrode 8A is embedded in a contact hole 7A formed so as to penetrate both of them. . The interlayer insulating film 7 is made of the silica-based cured film according to the present invention, like the interlayer insulating film 5. A counter electrode 8C is provided on the storage electrode 8A via a capacitor insulating film 8B made of a high dielectric material. The interlayer insulating films 5 and 7 may have the same composition or different compositions.

  The electronic component having the insulating coating according to the present invention configured as described above is provided with the silica-based cured coating according to the present invention that exhibits a low dielectric constant and a high mechanical strength. While achieving high performance such as a reduction in delay time, high reliability such as high process compatibility can be achieved.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, even when the surface tension of the film-improving liquid is greater than 21 mN / m, the ambient atmosphere is pressurized and / or the film is improved when the film-improving liquid penetrates into the silica-based film. It may be heated to such an extent that the working liquid does not boil. Thereby, suppression of the dielectric constant rise of a silica type cured film and improvement of mechanical strength can be achieved more efficiently. This is presumed to be due to the more efficient penetration of the coating-improving liquid into the pores of the silica-based coating.

  In addition, when the film-improving liquid contains a solvent, the surface tension of the film-improving liquid increases due to the large surface tension of the solvent. The surface tension of the working liquid may be reduced. Thereby, the effect similar to the above-mentioned pressurization and heating is acquired.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

<Preparation of composition for forming silica-based film>
A silica-based film forming composition was prepared by the following procedure. First, 137.5 g of tetraethoxysilane and 107.2 g of methyltriethoxysilane were charged into a 1000 mL flask. Next, 483.9 g of diethylene glycol dimethyl ether having a metal impurity concentration of 20 mass ppb or less was added to the flask, and the content was dissolved while stirring the flask at a speed of 200 revolutions / minute at room temperature.

  An aqueous solution obtained by dissolving 0.47 g of 60% by mass nitric acid in 71.98 g of water was dropped into this flask over 30 minutes with stirring. During the dropping, the solution temperature increased due to heat generation, but the solution was left as it was without being cooled with cooling water or the like. After completion of the dropping, the reaction was performed for 3 hours to obtain a polysiloxane solution. At this time, the liquid temperature had dropped to near room temperature.

  The obtained polysiloxane solution was heated in a hot bath at 65 to 85 ° C. under reduced pressure to distill off a part of the ethanol and the solvent diethylene glycol dimethyl ether produced by the above-mentioned treatment to obtain 533.3 g of a concentrated polysiloxane solution. Got. The weight average molecular weight of this solution measured by GPC method was 1120. The solid content concentration of the concentrated polysiloxane solution obtained by weighing 2 g of the solution in a metal petri dish and drying for 2 hours with a dryer at 150 ° C. was 15.0% by mass.

  Next, in another 1000 mL flask, 464.4 g of the concentrated polysiloxane solution described above, 20.34 g of polypropylene glycol (trade name: PPG725, manufactured by Aldrich) as a decomposable compound for pore formation, and diethylene glycol dimethyl ether 396 0.1 g, 2.46% by weight of tetramethylammonium nitrate aqueous solution (PH3.6) 14.6 g as the second catalyst, and 4.5 g of maleic acid aqueous solution diluted to 1% by weight as the second catalyst, respectively. The composition for forming a silica-based film was obtained by stirring and dissolving at room temperature for 30 minutes. The weight loss rate at 350 ° C. of the polypropylene glycol used as the decomposable compound was 99.9%.

<Preparation of coating film improving liquid>
(Synthesis Example 1)
In a 1000 mL flask, 990.0 g of hydrofluoroether (trade name: HFE-7200, manufactured by 3M) and 10.0 g of 1.8-diazabicyclo [5.4.0] undec-7-ene as the first catalyst Was dissolved for 3 hours while stirring at a rate of 200 revolutions / minute at room temperature to obtain a film-improving liquid of Synthesis Example 1.

  The surface tension of this film-improving liquid at 25 ° C. and 50% RH was measured using a Dunui surface tension tester (manufactured by Ito Manufacturing Co., Ltd.) and found to be 14 mN / m.

(Synthesis Example 2)
A film-improving liquid of Synthesis Example 2 was obtained in the same manner as Synthesis Example 1 except that 990.0 g of hydrofluoroether was replaced with 990.0 g of ethanol.

  It was 22 mN / m when the surface tension in 25 degreeC and 50% RH of this liquid for film improvement was measured using the Dunui surface tension tester (made by Ito Manufacturing Co., Ltd.).

  The surface tension of hydrofluoroether (manufactured by 3M, trade name: HFE-7200) at 25 ° C. and 50% RH was measured using a Dunui surface tension tester (manufactured by Ito Seisakusho Co., Ltd.). m.

<Formation of silica-based cured film>
Example 1
The above-mentioned composition for forming a silica-based film was applied on a 5-inch Si wafer as a substrate at 1100 rpm for 30 seconds by a spin coating method. Next, the coated substrate was heated on a hot plate in an N ₂ atmosphere at 250 ° C. for 3 minutes to remove volatile components, thereby obtaining a silica-based coating. The surface tension (critical surface tension) of this silica-based coating was derived by the above-described method and found to be 24 mN / m.

Next, an appropriate amount of the film-improving liquid of Synthesis Example 1 was poured onto the silica-based film and allowed to stand for 30 seconds, and then applied at 1100 rpm for 30 seconds by a spin coating method. Subsequently, the substrate after application of the coating improving liquid was heated on a hot plate in an N ₂ atmosphere at 250 ° C. for 30 seconds to remove volatile components. The substrate was heated at 350 ° C. for 30 minutes using a quartz tube furnace having an O ₂ concentration of about 100 ppm by volume to obtain a silica-based cured film according to Example 1. It was 0.2 micrometer when the film thickness of the silica type cured film which concerns on this Example 1 was measured using the ellipsometer.

(Example 2)
A silica-based film was obtained in the same manner as in Example 1. Next, an appropriate amount of the film-improving liquid of Synthesis Example 2 was poured onto the silica-based film, allowed to stand for 60 seconds in a pressure environment higher than normal pressure, and then applied at 1100 rpm for 30 seconds by a spin coating method. . Subsequently, the substrate after application of the coating improving liquid was heated on a hot plate in an N ₂ atmosphere at 250 ° C. for 30 seconds to remove volatile components. The substrate was heated at 350 ° C. for 30 minutes using a quartz tube furnace having an O ₂ concentration of about 100 ppm by volume to obtain a silica-based cured film according to Example 2. It was 0.2 micrometer when the film thickness of the silica type cured film which concerns on this Example 2 was measured using the ellipsometer.

(Comparative Example 1)
The silica-based cured coating film according to Comparative Example 1 was used in the same manner as in Example 1 except that liquid hydrofluoroether (manufactured by 3M, trade name: HFE-7200) was used instead of the coating film improving liquid of Synthesis Example 1. Got. It was 0.2 micrometer when the film thickness of the silica type cured film which concerns on this comparative example 1 was measured using the ellipsometer.

(Comparative Example 2)
The above-mentioned composition for forming a silica-based film was applied on a 5-inch Si wafer as a substrate at 1100 rpm for 30 seconds by a spin coating method. Next, the coated substrate was heated on a hot plate in an N ₂ atmosphere at 250 ° C. for 3 minutes to remove volatile components, thereby obtaining a silica-based coating. It was 24 mN / m when the surface tension of this silica type film was derived | led-out by the above-mentioned method.

Subsequently, the substrate on which the silica-based film was formed was heated on a hot plate at 250 ° C. for 30 seconds in an N ₂ atmosphere. Then, the substrate was heated at 350 ° C. for 30 minutes using a quartz tube furnace having an O ₂ concentration of about 100 ppm by volume to obtain a silica-based cured film according to Comparative Example 2. It was 0.2 micrometer when the film thickness of the silica type cured film which concerns on this Example 1 was measured using the ellipsometer.

<Evaluation of silica-based cured coating>
[Specific permittivity measurement]
On each of the silica-based cured coatings according to Examples 1 and 2 and Comparative Examples 1 and 2, an Al coating is formed with a film thickness of about 0.1 μm by a vacuum deposition method, and a Si wafer substrate, a silica-based cured coating, A structure in which Al coatings were laminated in this order was obtained. Using a device in which the charge capacity of this structure is connected to a dielectric test fixture (trade name: HP16451B, manufactured by Yokogawa Electric Corporation) to an LF impedance analyzer (trade name: HP4192A, manufactured by Agilent Technologies). The temperature was 23 ° C. ± 2 ° C., the humidity was 40% ± 10%, and the operating frequency was 10 kHz.
And the measured value of the charge capacity is expressed by the following formula (6);
(Relative permittivity of silica-based cured film) = 3.597 × 10−2 × (charge capacity <unit: pF>) × (film thickness of silica-based cured film <unit: μm>) (6)
And the relative dielectric constant of the silica-based cured coating was calculated. The results are shown in Table 1.

[Elastic modulus measurement]
As an index of the mechanical strength of the silica-based cured coating, its elastic modulus was measured by the following method. Using nanoindenter SA2 (DCM, manufactured by MTS) (temperature: 23 ° C. ± 2 ° C., frequency: 75 Hz, elastic modulus measurement range: 1/10 or less of the film thickness of the silica-based cured coating, indentation depth The elastic modulus of the silica-based cured coating was measured. The results are shown in Table 1.

1 is a schematic cross-sectional view showing a preferred embodiment of an electronic component according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Silicon wafer (substrate), 1A, 1B ... Diffusion region, 2A ... Field oxide film, 2B ... Gate insulating film, 3 ... Gate electrode, 4A, 4B ... Side wall oxide film, 5, 7 ... Interlayer insulating film (insulating film) 5A, 7A ... contact hole, 6 ... bit line, 8 ... memory cell capacitor (electronic component), 8A ... storage electrode, 8B ... capacitor insulating film, 8C ... counter electrode.

Claims (18)

A first step of allowing a liquid containing the first catalyst to penetrate into the silica-based coating formed on the substrate;
A second step of curing the silica-based coating after the first step to obtain a silica-based cured coating;
Have
A method for forming a silica-based cured coating, wherein the surface tension of the silica-based coating is greater than the surface tension of the liquid.   The method for forming a silica-based cured film according to claim 1, wherein the surface tension of the liquid is 21 mN / m or less.   The method for forming a silica-based cured coating according to claim 1 or 2, wherein the surface tension of the silica-based coating is 5 mN / m or more larger than the surface tension of the liquid.   In the first step, the liquid is infiltrated by a method of applying the liquid to the silica-based film, a method of immersing the silica-based film in the liquid, or spraying the liquid on the silica-based film. The formation method of the silica type cured film as described in any one of Claims 1-3 which is a method.   The method for forming a silica-based cured coating according to any one of claims 1 to 4, wherein the liquid further contains a solvent.   The method for forming a silica-based cured film according to any one of claims 1 to 5, wherein the first catalyst exhibits a catalytic action for a dehydration condensation reaction between silanol groups.   The first catalyst contains one or more compounds selected from the group consisting of a first acidic compound, a first basic compound, and a first onium salt compound. A method for forming a silica-based cured coating as described in 1.   The method for forming a silica-based cured film according to claim 7, wherein the first basic compound has a nitrogen atom in the molecule.   The method for forming a silica-based cured film according to any one of claims 5 to 8, wherein the solvent contains a solvent having a fluorine atom in the molecule.   The method for forming a silica-based cured coating according to any one of claims 1 to 9, wherein the silica-based cured coating has pores. The silica-based film has the following formula (1);
R ¹ _n SiX _4-n (1)
(Wherein R ¹ represents a group having a B atom, an N atom, an Al atom, a P atom, a Si atom, a Ge atom or a Ti atom, an organic group having 1 to 20 carbon atoms, or an H atom or an F atom; X represents a hydrolyzable group, n represents an integer of 0 to 2, and when n is 2, each R ¹ may be the same or different. When n is 0 to 2, each X may be the same May be different),
Obtained by applying a composition for forming a silica-based film containing a siloxane resin obtained by hydrolytic condensation of a compound represented by formula (1) onto a substrate to form a coating film, and removing the solvent contained in the coating film. The formation method of the silica type cured film as described in any one of Claims 1-10 which is what is obtained.   The method for forming a silica-based film according to claim 11, wherein the composition for forming a silica-based film further contains a second catalyst.   The method for forming a silica-based cured film according to claim 12, wherein the second catalyst exhibits a catalytic action for a dehydration condensation reaction between silanol groups.   The silica system according to claim 12 or 13, wherein the second catalyst contains one or more compounds selected from the group consisting of a second acidic compound, a second basic compound, and a second onium salt compound. Method for forming a cured film.   The method for forming a silica-based cured film according to claim 14, wherein the second basic compound has a nitrogen atom in the molecule.   A liquid for improving a silica-based cured film, which is the liquid used in the method for forming a silica-based cured film according to any one of claims 1 to 15.   A silica-based cured film that is provided on a substrate and is formed by the method for forming a silica-based cured film according to any one of claims 1 to 16. An electronic component, wherein the silica-based cured film according to claim 17 is formed on a substrate.

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