JP2003142476A - Porous silica thin film for insulation thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous silica thin film which has a low specific dielectric constant and mechanical strength enough for a CMP process in a copper wiring process for a semiconductor element. SOLUTION: This porous silica thin film is characterized in that a bridging coefficient is 70% or more, at least one or more scattering peaks exist within a scattering angle (2θ) of 0.5 to 3 deg. in an X-ray scattering measurement, and the surface density of a silanol group is 2% or less.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a porous silica thin film for an insulating thin film, and more specifically,
The present invention relates to a porous silica thin film having a low relative permittivity, stability, and mechanical strength capable of withstanding a chemical mechanical polishing (CMP) step in a copper wiring forming step.

[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 an insulating thin film material for a multilayer wiring structure of a semiconductor device 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, copper, which has a lower resistance, has begun to be used as a wiring material in place of conventional aluminum.

As a method for producing a porous silica thin film, JP-A-4-285081 discloses a sol-gel reaction of an alkoxysilane in the presence of a specific organic polymer to once prepare a silica / organic polymer composite. A method for producing and subsequently removing the organic polymer to obtain porous silica having a uniform pore size is disclosed. Japanese Patent Laid-Open No. 5-
85762 Publication and International Publication (WO) 99/0392
The pamphlet of No. 6 also discloses a method for obtaining porous silica having a very low dielectric constant, uniform pores and pore distribution, from a mixed system of alkoxysilane and an organic polymer.

However, even in these methods, porous silica having a sufficiently low relative dielectric constant, stable over time, and sufficient mechanical strength to withstand the CMP process has not been obtained. . In the present invention, C
The MP process is a process of polishing the surface of the excess copper on the insulating thin film, which is inevitably left when the copper to be the wiring is buried in the groove in the insulating thin film formed by etching, and flattening the surface. is there. In this process, not only the insulating thin film but also the barrier thin film on the thin film (usually depositing several hundred to several thousand Å of silicon oxide on the insulating thin film),
Since the compressive stress and the shear stress are applied, the insulating thin film is required to have mechanical strength.

[0005]

SUMMARY OF THE INVENTION That is, the present invention is to solve the above-mentioned problems, in which the porous silica thin film has a low relative permittivity and is stable, and has a high mechanical strength. The present invention provides a porous silica thin film that can sufficiently withstand the CMP process in the process.

[0006]

The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, the crosslinking rate of the porous silica thin film is 70% or more. It has been found that a porous silica thin film having a fine structure such that a scattering peak exists in the scattering angle region of and having a surface density of silanol groups of 2% or less solves the above problems. Completed the invention. Furthermore, the present invention can also achieve improved hygroscopicity.

That is, according to the present invention, (1) the crosslinking rate of the porous silica thin film is 70% or more,
In the X-ray scattering measurement of the porous silica thin film, the scattering angle (2
A porous silica thin film having at least one scattering peak between θ) of 0.5 and 3 ° and having a surface density of silanol groups of 2% or less in the porous silica thin film. . (2) A multilayer wiring structure including a plurality of insulating layers and wirings formed thereon, wherein at least one layer of the insulating layers is composed of the porous silica thin film described in (1). A multilayer wiring structure characterized by the following. (3) A semiconductor device including the multilayer wiring structure according to (2).

The present invention will be described in detail below. The porous silica of the present invention is a silica in which voids having an average pore diameter of 30 nm or less are uniformly dispersed, and the silica is
R ₁ x Hy SiO _{2 (2- (x + y) / 2)} having a hydrocarbon or hydrogen atom on silicon in addition to silicon oxide (SiO ₂ ) (wherein R ₁ has 1 to 8 carbon atoms ₎ . Represents a linear, branched or cyclic alkyl group or an aromatic group, and 0 ≦ x ≦ 2, 0 ≦ y
≦ 2 and 0 ≦ x + y <2. ) Is included.

The porous silica thin film of the present invention has a crosslinking rate of 70.
% Or more. In the present invention, the cross-linking ratio is represented by the ratio of the bonds that participated in cross-linking in the number of bonds of Si atoms existing in the porous silica thin film. That is,
It is defined as the ratio of the number of bonds in which the Si atom is bonded to the Si atom through a bonding group such as oxygen or an alkylene group, out of the total number of bonds represented by 4 times the number of moles of the Si atom in the thin film. Thus the bond which is not involved in the crosslinking is a bond, for example bound to R ₁ x and H and Si atoms _{R 1 x H y SiO (2-} (x + y) / 2).

When the crosslinking rate is 70% or more, the mechanical strength of the porous silica thin film is further increased, which is preferable. It is more preferably 80% or more. If it is less than 70 mol%, the mechanical strength becomes insufficient. The cross-linking rate is as described below.
It can be calculated based on the area of the Si signal by ²⁹ Si-NMR. The porous silica thin film of the present invention has a scattering angle (2θ) of 0.5 to 3 in X-ray scattering measurement.
It is characterized in that there is at least one or more scattering peaks between °. The scattering angle shows a peak at 0.5 ° to 3 ° when the pores of the porous silica thin film are regarded as spherical, depending on the filling state, but about 3 nm to about 30 n.
It means that there are pores having a very uniform pore size in the range of m. When the pore diameters are further homogenized, a plurality of peaks related to the periodicity of scattering can be seen within this scattering angle.

The uniformity of pore size correlates with the peak strength of the porous silica thin film, and the improvement of uniformity means the improvement of peak strength. If the scattering angle has a peak in a region of less than 0.5 °, the pore size becomes too large, and the gas or liquid diffuses into the thin film during processing, and the relative dielectric constant increases, which is not preferable. On the contrary, when the scattering angle has a peak in the region of 3 ° or more, the pores become too small and the relative dielectric constant may not decrease, which is not preferable.

The porous silica thin film of the present invention is characterized in that the surface density of silanol groups in the thin film is 2% or less. When the areal density of the silanol group is 2% or less, the hygroscopicity is remarkably improved, and the relative dielectric constant is 3 or less and is stable over time. Further, when the surface density of the silanol group is 1% or less, the relative dielectric constant also decreases, which is more preferable. It is more preferably 0.5% or less. In the present invention, the surface density (D) of silanol groups is defined by the following formula. D = {S / (ρt)} × 100 (%) where S is 900 to 960 cm in infrared absorption measurement
^-1 is the absorbance of the peak due to the Si-OH bond near ^-1 ,
ρ is the density of the porous silica thin film, and t is its thickness.

The method for producing the porous silica thin film of the present invention will be described below. The porous silica thin film of the present invention is produced by subjecting a coating composition containing a silica precursor obtained from an alkoxysilane as a starting material and a coating composition containing an organic polymer as a main component to a coating composition production step, and then applying the coating composition. The coating step of coating the substrate with a substrate to produce a coating film, followed by subjecting the coating film to a certain treatment to produce a silica thin film composed of a composite of silica and an organic polymer, and further removing the organic polymer to obtain the present invention. Of the porous silica thin film, and if the resulting thin film does not have a surface density of silanol groups of 2% or less, it can be further surface-treated. Hereinafter, the method for producing the porous silica thin film of the present invention will be described in detail in the order of each step.

First, the coating composition manufacturing process will be described. The coating composition of the present invention contains a silica precursor obtained from an alkoxysilane as a starting material and an organic polymer as main components. The coating composition of the present invention contains one or more substances selected from alkoxysilane as a raw material, a partial hydrolyzate thereof, a total hydrolyzate and an oligomeric condensate obtained by condensing the hydrolyzate, These are called silica precursors. Alkoxysilane, which is a raw material of the silica precursor, can be roughly classified into 1 to 4 functional ones based on its structure.

Specific examples of the tetrafunctional alkoxysilane of the present invention include tetramethoxysilane, tetraethoxysilane, tetra (n-propoxy) silane and tetra (i-).
Propoxy) silane, tetra (n-butoxy) silane,
Tetra (sec-butoxy) silane, tetra (tert-)
Butoxy) silane and the like. Among these tetrafunctional alkoxysilanes, tetramethoxysilane and tetraethoxysilane are particularly preferable.

Next, specific examples of the 1-3 functional alkoxysilane will be shown. For example, trifunctional alkoxysilanes include methyltrimethoxysilane, methyltriethoxysilane, methyltri-n-propoxysilane, and methyltri-.
iso-propoxysilane, methyltri-n-butoxysilane, methyltri-sec-butoxysilane, methyltri
-tert-butoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltri-n-propoxysilane, ethyltri-iso-propoxysilane, ethyltri-n-butoxysilane, ethyltri-sec-butoxysilane, ethyltri-tert-butoxysilane , N
-Propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltri-n-propoxysilane, n-
Propyltri-iso-propoxysilane, n-propyltri-n-butoxysilane, n-propyltri-sec-butoxysilane, n-propyltri-tert-butoxysilane, i-propyltrimethoxysilane, i-propyltriethoxy Silane, i-propyltri-n-propoxysilane, i-propyltri-iso-propoxysilane, i-
Propyltri-n-butoxysilane, i-propyltri-s
ec-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-i-triethoxysilane, sec-butyl-tri-n-propoxysilane, s
ec-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-butyltri-tert-butoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltri-n-propoxysilane, phenyltri-iso-propoxysilane, phenyltri-n-butoxysilane, phenyl Examples include tri-sec-butoxysilane and phenyltri-tert-butoxysilane. Of these, particularly preferred compounds are methyltrimethoxysilane and methyltriethoxysilane.
A partial hydrolyzate of an alkoxysilane may be used as a raw material.

Specific examples of the bifunctional alkoxysilane include dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldi (n-propoxy) silane, dimethyldi (i-propoxy) silane and dimethyldi (n-).
Butoxy) silane, dimethyldi (sec-butoxy) silane, dimethyldi (tert-butoxysilane), diethyldimethoxysilane, diethyldiethoxysilane, diethyldi (n-propoxy) silane, diethyldi (i-
Propoxy) silane, diethyldi (n-butoxy) silane, diethyldi (sec-butoxy) silane, diethyldi (tert-butoxysilane), dipropyldimethoxysilane, dipropyl (n-butoxy) silane, dipropyldiethoxysilane, dipropyl (sec) -Butoxy) silane, dipropyldi (n-propoxy) silane, dipropyl (tert-butoxy) silane, dipropyldi (i-
Propoxy) silane, diphenyldimethoxysilane, diphenyldiethoxysilane, diphenyldi (n-propoxy) silane, diphenyldi (i-propoxy) silane, diphenyldi (n-butoxy) silane, diphenyldi (sec-butoxy) silane, diphenyl Ji (ter
t-butoxysilane), methylethyldimethoxysilane, methylethyldiethoxysilane, methylethyldi (n-propoxy) silane, methylethyldi (i-propoxy) silane, methylethyldi (n-butoxy) silane, methylethyldi (sec-butoxy) silane, methylethyldi (Tert-butoxysilane), methylpropyldimethoxysilane, methylpropyldiethoxysilane, methylpropidi (n-propoxy) silane, methylpropyldi (i-propoxy) silane, methylpropyldi (n-butoxy) silane, methylpropyldi ( sec
-Butoxy) silane, methylpropyldi (tert-butoxysilane), methylphenyldimethoxysilane, methylphenyldiethoxysilane, methylphenyldi (n-
Propoxy) silane, methylphenyldi (i-propoxy) silane, methylphenyldi (n-butoxy) silane, methylphenyldi (sec-butoxy) silane, methylfaildi (tert-butoxysilane), ethylphenyldimethoxysilane, ethyl Phenyldiethoxysilane, ethylphenyldi (n-propoxy) silane,
Ethylphenyldi (i-propoxy) silane, ethylphenyldi (n-butoxy) silane, ethylphenyldi (sec-butoxy) silane, ethylphenyldi (te
rt-butoxysilane), etc., and an alkylsilane having two alkyl groups or aryl groups bonded to a silicon atom.

Further, methylvinyldimethoxysilane, methylvinyldiethoxysilane, methylvinyldi (n-propoxy) silane, methylvinyldi (i-propoxy)
Silane, methylvinyldi (n-butoxy) silane, methylvinyldi (sec-butoxy) silane, methylvinyldi (tert-butoxysilane), divinyldimethoxysilane, divinyldiethoxysilane, divinyldi (n-
1 to 2 vinyl groups are bonded to a silicon atom such as propoxy) silane, divinyldi (i-propoxy) silane, divinyldi (n-butoxy) silane, divinyldi (sec-butoxy) silane, divinyldi (tert-butoxysilane). Alkylsilanes and the like are also suitable.

Specific examples of the monofunctional alkoxysilane include trimethylmethoxysilane, trimethylethoxysilane, trimethyl (n-propoxy) silane, trimethyl (i-propoxy) silane, trimethyl (n-butoxy) silane and trimethyl (sec). -Butoxy) silane, trimethyl (tert-butoxysilane), triethylmethoxysilane, triethylethoxysilane, triethyl (n-propoxy) silane, triethyl (i-propoxy) silane, triethyl (n-butoxy) silane, triethyl (sec-butoxy) ) Silane, triethyl (tert-butoxysilane), tripropylmethoxysilane, tripropylethoxysilane, tripropyl (n-propoxy) silane, tripropyl (i-propoxy) silane, tripropyl (N-butoxy) silane,
Tripropyl (sec-butoxy) silane, tripropyl (tert-butoxysilane), triphenylmethoxysilane, triphenylethoxysilane, triphenyl (n-propoxy) silane, triphenyl (i-propoxy) silane, triphenyl (n -Butoxy) silane,
Triphenyl (sec-butoxy) silane, triphenyl (tert-butoxysilane), methyldiethylmethoxysilane, methyldiethylethoxysilane, methyldiethyl (n-propoxy) silane, methyldiethyl (i
-Propoxy) silane, methyldiethyl (n-butoxy) silane, methyldiethyl (sec-butoxy) silane, methyldiethyl (tert-butoxysilane), methyldipropylmethoxysilane, methyldipropylethoxysilane, methyldipropyl (n- Propoxy) silane, methyldipropyl (i-propoxy) silane, methyldipropyl (n-butoxy) silane, methyldipropyl (sec-butoxy) silane, methyldipropyl (t
ert-butoxysilane), methyldiphenylmethoxysilane, methyldiphenylethoxysilane, methyldiphenyl (n-propoxy) silane, methyldiphenyl (i-propoxy) silane, methyldiphenyl (n-butoxy) silane, methyldiphenyl (sec-butoxy). Silane, methyldiphenyl (tert-butoxysilane), ethyldimethylmethoxysilane, ethyldimethylethoxysilane, ethyldimethyl (n-propoxy)
Silane, ethyldimethyl (i-propoxy) silane, ethyldimethyl (n-butoxy) silane, ethyldimethyl (sec-butoxy) silane, ethyldimethyl (ter
t-butoxysilane), ethyldipropylmethoxysilane, ethyldipropylethoxysilane, ethyldipropyl (n-propoxy) silane, ethyldipropyl (i-
Propoxy) silane, ethyldipropyl (n-butoxy) silane, ethyldipropyl (sec-butoxy) silane, ethyldipropyl (tert-butoxysilane), ethyldiphenylmethoxysilane, ethyldiphenylethoxysilane, ethyldiphenyl (n-propoxy) ) Silane, ethyldiphenyl (i-propoxy) silane, ethyldiphenyl (n-butoxy) silane, ethyldiphenyl (sec-butoxy) silane, ethyldiphenyl (tert-butoxysilane), propyldimethylmethoxysilane, propyldimethylethoxysilane, propyl Dimethyl (n-propoxy) silane, propyldimethyl (i-propoxy) silane, propyldimethyl (n-butoxy) silane, propyldimethyl (sec-
Butoxy) silane, propyldimethyl (tert-butoxysilane), propyldiethylmethoxysilane, propyldiethylethoxysilane, propyldiethyl (n-
Propoxy) silane, propyldiethyl (i-propoxy) silane, propyldiethyl (n-butoxy) silane, propyldiethyl (sec-butoxy) silane, propyldiethyl (tert-butoxysilane), propyldiphenylmethoxysilane, propyldiphenylethoxysilane, Propyldiphenyl (n-propoxy) silane, propyldiphenyl (i-propoxy) silane,
Propyldiphenyl (n-butoxy) silane, propyldiphenyl (sec-butoxy) silane, propyldiphenyl (tert-butoxysilane) phenyldimethylmethoxysilane, phenyldimethylethoxysilane, phenyldimethyl (n-propoxy) silane, phenyldimethyl (i- Propoxy) silane, phenyldimethyl (n-butoxy) silane, phenyldimethyl (sec-
Butoxy) silane, phenyldimethyl (tert-butoxysilane), phenyldiethylmethoxysilane, phenyldiethylethoxysilane, phenyldiethyl (n-
Propoxy) silane, phenyldiethyl (i-propoxy) silane, phenyldiethyl (n-butoxy) silane, phenyldiethyl (sec-butoxy) silane, phenyldiethyl (tert-butoxysilane), phenyldipropylmethoxysilane, phenyldipropylethoxy Silane, phenyldipropyl (n-propoxy) silane, phenyldipropyl (i-propoxy) silane,
Examples thereof include phenyldipropyl (n-butoxy) silane, phenyldipropyl (sec-butoxy) silane, phenyldipropyl (tert-butoxysilane) and the like.

Further, a monofunctional alkylsilane having 1 to 3 vinyl groups or alkyl groups bonded to a silicon atom is also suitable. Specifically, trivinylmethoxysilane, trivinylethoxysilane, trivinyl (n-propoxy) silane, trivinyl (i-propoxy) silane, trivinyl (n-butoxy) silane, trivinyl (sec-butoxy) silane, trivinyl (tert). -Butoxysilane), vinyldimethylmethoxysilane, vinyldimethylethoxysilane, vinyldimethyl (n-propoxy) silane, vinyldimethyl (i-propoxy) silane, vinyldimethyl (n-butoxy) silane, vinyldimethyl (sec-butoxy) silane , Vinyldimethyl (tert-butoxysilane), vinyldiethylmethoxysilane, vinyldiethylethoxysilane, vinyldiethyl (n-propoxy) silane, vinyldiethyl (i-
Propoxy) silane, vinyldiethyl (n-butoxy)
Silane, vinyldiethyl (sec-butoxy) silane,
Vinyldiethyl (tert-butoxysilane), vinyldipropylmethoxysilane, vinyldipropylethoxysilane, vinyldipropyl (n-propoxy) silane,
Vinyldipropyl (i-propoxy) silane, vinyldipropyl (n-butoxy) silane, vinyldipropyl (sec-butoxy) silane, vinyldipropyl (te
rt-butoxysilane) and the like.

The above-mentioned alkoxysilanes are used as the monofunctional and difunctional alkoxysilanes of the present invention. Among them, more preferred are trimethylmethoxysilane, trimethylethoxysilane, triethylmethoxysilane, Such as triethylethoxysilane, tripropylmethoxysilane, tripropylmethoxysilane, tripropylethoxysilane, triphenylmethoxysilane, triphenylethoxysilane, phenyldimethylmethoxysilane, phenyldimethylethoxysilane, diphenylmethylmethoxysilane, diphenylmethylethoxysilane, etc. Alkylsilane, dimethyldiethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, diphenyldiethoxysilane, methylethyldiethoxysilane , Methylphenyl diethoxy silane, ethyl phenyl diethoxy silane, dimethyl dimethoxy silane, dimethyl dimethoxy silane, diethyl dimethoxy silane, diphenyl dimethoxy silane, methyl ethyl dimethoxy silane, methyl phenyl dimethoxy silane, and that such ethylphenyl dimethoxysilane.

Further, a hydrogen atom is directly bonded to a silicon atom such as methyldimethoxysilane, methyldiethoxysilane, ethyldimethoxysilane, ethyldiethoxysilane, propyldimethoxysilane, propyldiethoxysilane, phenyldimethoxysilane and phenyldiethoxysilane. It is also possible to use the prepared one. Also, bis (ethoxydimethylsilyl) methane, bis (ethoxydiphenylsilyl) methane, bis (ethoxydimethylsilyl) ethane, bis (ethoxydiphenylsilyl) ethane, 1,
3-bis (ethoxydimethylsilyl) propane, 1,3
-Bis (ethoxydiphenylsilyl) propane, 3-diethoxy-1,1,3,3-tetramethyldisiloxane,
1,3-diethoxy-1,1,3,3-tetraphenyldisiloxane, 1,2-diethoxy-1,1,2,2-tetramethyldisilane, 1,2-diethoxy-1,1,2,
2-Tetraphenyldisilane or the like may be used.

The porous silica thin film of the present invention has a crosslinking ratio of 70.
%, But the content can be controlled substantially by the charged composition of the alkoxysilane which is the raw material of the silica precursor in the coating composition.
For example, TEOS1 which is a tetrafunctional alkoxysilane
It is about 88% when it is assumed that 100 mol of MTES and 1 mol of MTES are charged and both alkoxysilanes are 100% hydrolyzed and condensed to participate in crosslinking. On the other hand, 2 mol of bis (triethoxysilyl) ethane containing multiple silicon atoms in one molecule
When is further added, the two Si—C bonds of Si—CH ₂ CH ₂ —Si are used as the bonds involved in the crosslinking, and thus the crosslinking rate is about 94%.

Next, the organic polymer in the present invention will be described. First, the organic polymer that can be used in the present invention has a low thermal decomposition temperature when the organic polymer is removed from the composite film of silica and the organic polymer as described below by heating and firing to be converted into a porous silica thin film, And a linear or branched block copolymer of two or more elements having a proper compatibility with a silica precursor and silica, and a block portion having a linear or cyclic oxyalkylene group having 1 to 8 carbon atoms. Is a repeating unit, and one block contains 60% by weight or more of the block copolymer unit.

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 polyethylene glycol polypropylene glycol, polyethylene glycol polybutylene glycol, and the like 2.
Mention may be made of original block copolymers as well as polyether block copolymers such as linear ternary block copolymers such as polyethylene glycol polypropylene glycol polyethylene glycol, polypropylene glycol polyethylene glycol polypropylene glycol, polyethylene glycol polybutylene glycol polyethylene glycol. Furthermore, 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 / or hydroxyl acid It is preferable that at least three of the contained hydroxyl groups and carboxyl groups have a structure in which block copolymer chains are bonded. Specifically, branched 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 in addition to the above sugar chains include sorbitol, mannitol, xylitol, threitol, maltitol, arabitol, lactitol, adonitol, cellobiitol, glucose, fructose, sucrose, lactose, Mannose, galactose, erythrose, xylulose, allulose, ribose, sorbose, xylose, arabinose, isomaltose, dextrose,
Glucoheptose etc. are mentioned. Further, specific examples of the hydroxyl acid, citric acid, malic acid, tartaric acid, gluconic acid, glucuronic acid, glucoheptonic acid, glucooctanoic acid, threonic acid, saccharic acid, galactonic acid, galactaric acid, galacturonic acid, glyceric acid, Examples thereof include hydroxysuccinic acid.

Further, in the present invention, it is also possible to use a linear higher aliphatic / alkylene oxide block copolymer obtained by addition-polymerizing an alkylene oxide with an aliphatic higher alcohol. Specifically, polyoxyethylene lauryl ether, polyoxypropylene lauryl ether, polyoxyethylene oleyl ether, polyoxypropylene oleyl ether, polyoxyethylene cetyl ether, polyoxypropylene cetyl ether, polyoxyethylene stearyl ether, polyoxypropylene stearyl. Examples include ether.

The terminal group of the above block copolymer is not particularly limited, but is a group modified with a hydroxyl group, a linear or cyclic alkyl ether group, an alkyl ester group, an alkylamide group, an alkyl carbonate group, a urethane group or a trialkylsilyl group. Is preferred. In addition to the above block copolymer, the organic polymer used in the present invention is more effective when the contained polymer is a polymer in which at least one of the polymer end groups has a group chemically inactive to the silica precursor. Play. That is, by using this polymer in combination with the block copolymer, the organic polymer is more easily removed from the silica / organic polymer composite thin film.

The polymer having at least one end group 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 have 1 to 8 carbon atoms.
Examples thereof include linear, branched, and cyclic alkyl ether groups, alkyl ester groups, alkyl amide groups, and alkyl carbonate groups.

The main chain skeleton structure of the polymer is not particularly limited, but specific examples include polyether, polyester, polycarbonate, polyanhydride, polyamide, polyurethane, polyurea, polyacrylic acid, polyacrylic ester, poly Methacrylic acid,
Polymethacrylic acid ester, polyacrylamide, polymethacrylamide, polyacrylonitrile, polymethacrylonitrile, polyolefin, polydiene, polyvinyl ether, polyvinyl ketone, polyvinylamide, polyvinylamine, polyvinyl ester, polyvinyl alcohol, polyvinyl halide, polyhalogenated Examples thereof include vinylidene, polystyrene, polysiloxane, polysulfide, polysulfone, polyimine, polyimide, cellulose, and polymers containing these derivatives as main constituent components.

It is also possible to use a copolymer of monomers as constituent units of these polymers or a copolymer with any other monomer. The organic polymer may be used alone or in combination of two or more. Among the above polymers, those preferably used are those which disappear by heating and are easily converted into porous silicon oxide, aliphatic polyether, aliphatic polyester, aliphatic polycarbonate, and aliphatic polyanhydride as main constituent components. Is also a polymer. 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.

As an example of the aliphatic polyether of the present invention,
The main chain is an alkylene glycol such as polyethylene glycol, polypropylene glycol, polyisobutylene glycol, polytrimethylene glycol, polytetramethylene glycol, polypentamethylene glycol, polyhexamethylene glycol, polydioxolane, and polydioxepane, and at least one end thereof is Alkyl ether, alkyl ester, alkyl amide,
Examples thereof include those that have been alkylcarbonated. 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 glycol 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 polyether having an ester group at the terminal, at least one terminal of the above-mentioned 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, polyethylene glycol biscarboxymethyl ether dimethyl ester, polypropylene glycol biscarboxymethyl ether dimethyl Preferred examples include esters, glycerin polyethylene glycol triacetate, pentaerythritol polyethylene glycol tetraacetate, pentitol polyethylene glycol pentaacetate and sorbitol polyethylene glycol hexaacetate.

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 amidation is carried out. Examples of the amidation method include 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 and bis-tert-butoxycarbonyloxy polyethylene glycol.

Furthermore, 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 polymerization products of lactones, and polyethylene oxalate, polyethylene succinate, polyethylene adipate, polyethylene sebac. Cations, polypropylene adipates, polyoxydiethylene adipates, and other polycondensates of dicarboxylic acids and alkylene glycols, as well as ring-opening copolymers of epoxides and acid anhydrides, the alkyl ether group being at least one terminal of the polymer. , Those modified with an alkyl ester group, an alkyl amide group, an alkyl carbonate group, a urethane group, and a trialkylsilyl group.

Examples of the aliphatic polycarbonate include polycarbonate 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 the aliphatic polyanhydride include dicarboxylic acids such as polymalonyl oxide, polyadipoyl oxide, polypimeloyl oxide, polysuberoyl oxide, polyazela oil oxide and polysebacyl oxide as the main chain portion. Examples of the polycondensation product include a 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 at least at one end of the polymer. You can

The alkylene glycol means a dihydric alcohol obtained by substituting two hydrogen atoms, which are not bonded on the same carbon atom of an alkane having 2 or more carbon atoms, with hydroxyl groups. Dicarboxylic acids are oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid,
It refers to an organic acid having two carboxyl groups such as suberic acid, azelaic acid and sebacic acid.

Further, since the terminal group of the present invention has particularly good compatibility with the silica precursor, a branched polymer is preferable as the polymer form because it can have more terminal groups in the molecule. The use of a branched polymer is more preferable because the compatibility is improved and thus the homogeneity of the composite of silica and the organic polymer is further improved, and as a result, the surface of the thin film is further improved.

The polymer having an end group as described above may have a structure in which at least three of the hydroxyl groups contained in the sugar chain are bonded, such as a block copolymer. Further, in the present invention, an organic polymer having at least one polymerizable functional group in the molecule can also be used. The use of such a polymer improves the strength of the porous thin film, although the reason is not clear.

The polymerizable functional group is a 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.

The organic polymer is not particularly limited as long as it has at least one polymerizable functional group in the molecular chain, and specific examples thereof include polyether, polyester, polycarbonate, polyanhydride, polyamide, polyurethane, polyurea. , Polyacrylic acid,
Polyacrylic acid ester, polymethacrylic acid, polymethacrylic acid ester, polyacrylamide, polymethacrylamide, polyacrylonitrile, polymethacrylonitrile, polyolefin, polydiene, polyvinyl ether, polyvinyl ketone, polyvinylamide, polyvinylamine, polyvinyl ester, polyvinyl alcohol ,
Examples thereof include polyvinyl halides, polyvinylidene halides, polystyrenes, polysiloxanes, polysulfides, polysulfones, polyimines, polyimides, celluloses, and polymers containing these derivatives as main constituent components. You may use the copolymer of the monomers which are a structural unit of these polymers, and the copolymer with other arbitrary monomers. The organic polymer may be used alone or in combination of two or more.

Among the above polymers, those preferably used are polyether, polyester, polycarbonate, polyanhydride, polyamide, polyurethane, polyurea, polyacrylic acid, polyacrylic acid ester, polymethacrylic acid, polymethacrylic acid ester,
It mainly contains polyacrylamide, polymethacrylamide, polyvinylamide, polyvinylamine, polyvinyl ester, polyvinyl alcohol, polyimine, and polyimide. Further, in the case of converting into a porous silicon oxide by heating and firing as described later, an aliphatic polyether, an aliphatic polyester, an aliphatic polycarbonate, and an aliphatic polyanhydride having a low thermal decomposition temperature are used as main constituent components. It is particularly preferable to use one.

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,
Alkyl refers to C1-C8 alkyl groups and aryl groups such as phenyl, tolyl, and anisyl groups,
(Meth) acrylate refers to both acrylate and methacrylate, and dicarboxylic acid refers to organic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, 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, etc., having a vinyl group, a glycidyl group in the side chain,
Polyacrylic acid esters and polymethacrylic acid esters having functional groups such as allyl groups. (H) Polyvinyl cinnamate, polyvinyl azidobenzal, epoxy resin and the like. Among these, aliphatic polyethers, aliphatic polyesters, aliphatic polycarbonates, aliphatic polyanhydrides, etc., which are easily converted into a porous silica thin film by heating and firing as described later, are particularly preferably used.

Specific examples of the organic polymers that can be used in the present invention have been given above. The number average molecular weight of the organic polymers is 100 to 1,000,000, preferably 100 to 300,000.
More preferably, it is 200 to 50,000. When the molecular weight is 100 or less, the organic polymer is removed from the silica / organic polymer composite too quickly to obtain a porous silica thin film having a desired porosity, and the polymer molecular weight is 100. If it exceeds 10,000, the removal rate of the polymer is too slow and the polymer remains, which is not preferable. In particular, a more preferable polymer has a molecular weight of 200 to 5
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. What should be noted here is that the pore size of the porous silica thin film 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
Siloxane 1 obtained by assuming that the total amount of the starting material alkoxysilane charged has undergone hydrolysis and condensation reactions
0.01 to 10 parts by weight, preferably 0.0
It is 5 to 5 parts by weight, more preferably 0.5 to 3 parts by weight. If the amount of the organic polymer added is less than 0.01 parts by weight, a porous body having sufficient pores cannot be obtained, and even if it is more than 10 parts by weight, a porous silica thin film having sufficient mechanical strength cannot be obtained. , Poor in practicality. It should be noted that with siloxane obtained assuming that the total amount of charged alkoxysilane has undergone hydrolysis and condensation reactions, the alkoxy groups directly linked to Si atoms are 100% hydrolyzed to SiOH, and further 100% condensed to form a siloxane structure. Say what has become.

The coating composition of the present invention can be obtained by mixing the above-mentioned alkoxysilane with an organic polymer. At least a part of the alkoxysilane is hydrolyzed and polycondensed to give a hydrolysis product of the alkoxysilane. It is desirable to be condensed in an oligomer form. Since hydrolysis and polycondensation increase the viscosity of the coating composition to an appropriate level,
The shape retention of the coating film can be secured and the film thickness can be made uniform. Furthermore, when the silica precursor gels to form silica, the formation of the silica skeleton occurs mildly, so that the film shrinkage is less likely to occur. 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 alkoxysilane treatment conditions are usually 0 to 150 in the presence of water necessary for hydrolysis.
℃, preferably 0 to 100 ℃, more preferably 0 ℃ to 5
It may be processed at 0 ° C. 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, the hydrolysis also includes partial hydrolysis. For example, in the case of a tetrafunctional alkoxysilane, it is not necessary for all four alkoxy groups to be hydrolyzed, for example, only one is hydrolyzed, two or more are hydrolyzed, Alternatively, a mixture of these may be present. Polycondensation is a condensation of silanol groups obtained by hydrolysis of alkoxysilane to form Si-O-Si bonds, but it is not necessary that all silanol groups are condensed, It does not matter even if the silanol groups are condensed,
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.
In addition, 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 hydrolyzes to silanol in the presence of water, and then grows into an oligomeric silica precursor having a siloxane bond by a condensation reaction between silanol groups.

The total solid content concentration of the coating composition in the present invention is preferably 2 to 30% by weight, but depending on the purpose of use, concentration or propylene glycol monoethyl ether,
Propylene glycol monopropyl ether, N, N-
Dimethylformamide, methyl acetate, ethyl acetate, γ-
It is appropriately adjusted by dilution with a solvent such as butyrolactone, methyl lactate, ethyl lactate, n-butyl lactate, diethyl malonate, dimethyl phthalate or diethyl phthalate. When the total solid content concentration of the coating composition is 2 to 30% by weight, the film thickness of the coating film when formed into a coating film in the subsequent step is in an appropriate range, and the storage stability of the coating composition itself is more excellent. Is. The total solid content concentration is determined as the weight% of the siloxane compound obtained by hydrolysis and condensation reaction of all alkoxysilanes in the coating composition.

The coating composition of the present invention comprises a mixture of the above silica precursor and an organic polymer. In the present invention, an acid may be used to accelerate the hydrolysis and condensation reaction of alkoxylane. . As a specific example, hydrochloric acid,
Inorganic acids such as nitric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, tripolyphosphoric acid, phosphonic acid and phosphinic acid can be mentioned. Examples of the organic acid include 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. Acid, butyric acid, mellitic 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,
Examples thereof include monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, trifluoroacetic acid, formic acid, malonic acid, sulfonic acid, phthalic acid, fumaric acid, citric acid, tartaric acid, succinic acid and isonicotinic acid.

Also included are compounds which function as an acid after the coating composition of the present invention has been applied to a substrate. 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 alkoxy group of the alkoxysilane compound charged as the starting material. 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.

In addition, if desired, components such as colloidal silica and a surfactant may be added,
A photocatalytic generator for imparting photosensitivity, an adhesiveness improver for enhancing the adhesiveness with the substrate, an optional additive such as a stabilizer for long-term storage may be used in the range of the present invention without impairing the gist of the present invention. It is also possible to add it to the coating composition. Further, the content of alkali metals such as sodium and potassium and iron in the coating composition is 50 ppb or less, particularly 10 ppb.
The following is preferable from the viewpoint of low leak current of the coating film. Alkali metal and iron may be mixed from the raw materials used, and it is preferable to purify the alkoxysilane and the organic polymer.

Next, the coating step of coating the coating composition to form a coating film will be described. In the present invention, a coating film is formed by coating a coating composition on a substrate. 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. 100
If it is thicker than μm, cracks may occur. An insulating layer for a multilayer wiring structure of a semiconductor element is usually 0.1
It is used in the range of 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 coating film, the surface of the substrate may be treated with an adhesion improver in advance. 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 coating film obtained through the above coating process is
Subsequently, the composite thin film of silica and organic polymer is formed by gelling, and the porous thin film of the present invention is obtained through the porous thin film manufacturing process of removing the organic polymer and making it porous. The porous thin film manufacturing process will be described below. The coating film becomes a composite film of silica and an organic polymer in which the hydrolysis / condensation reaction of the silica precursor present in the coating composition further progresses due to gelation and the condensation rate increases.

In the present invention, the alkoxysilane is hydrolyzed and polycondensed so that the condensation rate is about 90% or more is called gelation, and the gelled one is called silica. The gelling temperature is not particularly limited, but is usually 100 to 300 ° C,
The temperature is preferably 150 to 300 ° C., and the time required for the gelation reaction is usually in the range of several seconds to 10 hours, although it varies depending on the heat treatment temperature, the catalyst addition amount, the solvent species and the amount. It is preferably 30 seconds to 5 hours, more preferably 1 minute to 2 hours. 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. If it is higher than 300 ° C,
Giant voids are likely to be formed, and the homogeneity of the composite thin film of silica and organic polymer described later is deteriorated.

The condensation rate of silica may reach up to 100%, but it is usually about 90%. The condensation rate in this case can be determined by ²⁹ Si-NMR analysis of the solid or the like. The silica-organic polymer composite film thus obtained has a low dielectric constant and is capable of forming a thick film. Therefore, it can be used as it is as an insulating portion of a wiring, or it can be used for an application other than a thin film such as an optical film. It can also be used as a film, a structural material, a film, a coating material and the like. However, it is preferable to convert it into a porous silica thin film for the purpose of obtaining a material having a lower dielectric constant as an insulator of the LSI multilayer wiring.

From the composite film of silica and organic polymer to the insulating porous silica thin film, the organic polymer is removed. At this time, if the gelling reaction has proceeded sufficiently, the region occupied by the organic polymer remains as voids in the porous silica thin film without being crushed. As a result, a porous silica thin film having a high porosity and a low dielectric constant can be obtained. Examples of the method for removing the organic polymer include heating, plasma treatment, solvent extraction and the like, but heating is the 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. In addition, a large amount of pollutant gas is generated. Conversely 45
Treatment at a temperature higher than 0 ° 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 in the range of 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, the evaporation and decomposition of the organic polymer will not proceed sufficiently, so that organic substances remain as impurities in the resulting porous silica thin film, and the dielectric constant does not decrease. 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 such as nitrogen, argon or helium. 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, the presence of ammonia, hydrogen or the like in the atmosphere to deactivate the silanol groups remaining in the silica can reduce the hygroscopicity of the porous silica thin film and suppress the increase in the dielectric constant. In the present invention, if the step of removing the organic polymer after the step of forming the composite film of silica and the organic polymer is carried out under the above-mentioned conditions, before and after the step, a step of arbitrary temperature and atmosphere is performed. There is no problem.

As the heating apparatus which can be used 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.

In the present invention, when the silanol surface density of the thin film obtained through the above steps does not satisfy 2% or less,
The surface density of silanol can be easily reduced to 2% or less by performing the following surface treatment process. That is, in the present invention, the density of silanol groups is controlled by, after the porous silica thin film is produced, one or both of a chemical method such as a surface treatment agent and a physical method such as heat treatment, or a combination thereof.

The surface treatment process for controlling the surface density of silanol groups will be described below. As the surface treatment agent for controlling the density of silanol groups, for example, a silane coupling agent can be used. As the silane coupling agent, alkylsilazane, alkylalkoxysilane, alkylsilyl halide and the like can be used.

Specific examples of the silane coupling agent include, for example, hexamethyldisilazane, hexaethyldisilazane, 1,1,3,3,5,5-hexamethylcyclotrisilazane, 1,2,3. , 4,5,6-hexamethylcyclotrisilazane, hexapropylcyclotrisilazane, hexabutylcyclotrisilazane, trimethylsilyldimethylamine, trimethylsilyldimethylamine, dimethylsilyldimethylamine, dimethylsilyldiethylamine, bisdiethylaminodimethylsilane, bisdimethylamino Diethylsilane, bisdimethylaminodimethylsilane, bisdimethylaminodiphenylsilane, bisdiethylaminomethylsilane, diisopropylaminotrimethylsilane, heptamethyldisilazane, N
-Methyl-N trimethylsilyltrifluoroacetamide, nonamethyltrisilazane, octamethylcyclotetrasilazane, n-octyldimethyldimethylaminosilane, 1,3,5,7-tetraethyl-2,4,6,8-
Tetramethylcyclotetrasilazane, tetrakisdimethylaminosilazane, 2,2,5,5-tetramethyl-
2,5-disila-1-azacyclopentane, 1,1,
3,3-tetramethyldisilazane, tetraphenyldimethyldisilazane, 1,2,3, -triethyl-2,4
6-trimethylcyclotrisilazane, 1,1,3,3
5,5,7,7-octamethylcyclotetrasilazane,
Trisdimethylaminomethylsilane, bisdimethylaminodiethylsilane, bisdimethylaminoethylsilane,
As a silazane such as bisdimethylaminodimethylsilane, bisdimethylaminomethylsilane, N, N'bis (trimethylsilyl) urea, N-trimethylsilylacetamide, trimethylsilylimidazole, or alkylalkoxysilanes, an alkyl group or an aryl group on the above silicon atom. Group bonded trimethylmethoxysilane, trimethylethoxysilane, triethylmethoxysilane, triethylethoxysilane, tripropylmethoxysilane, triphenylmethoxysilane, triphenylethoxysilane, phenyldimethylmethoxysilane, phenyldimethylethoxysilane, diphenylmethylmethoxysilane , Diphenylmethylethoxysilane, 2-trimethylsiloxypropene, etc. directly containing three alkyl groups or alkyl groups on the silicon atom. Alkylsilane bonded to a reel group, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, methylethyldimethoxysilane, methyl An alkylsilane in which two alkyl groups or aryl groups are directly bonded to a silicon atom, such as ethyldiethoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane, ethylphenyldimethoxysilane, and ethylphenyldiethoxysilane, and the above-mentioned. An alkoxysilane in which one alkyl group or aryl group is directly bonded to a silicon atom can be mentioned.

Further, those having a hydrogen atom on a silicon atom such as methyldiethoxysilane, dimethylvinylmethoxysilane and dimethylvinylethoxysilane can also be used. Further, bis (trimethoxysilyl) methane, bis (triethoxysilyl) methane, 1,2-bis (trimethoxysilyl) ethane, 1,2-bis (triethoxysilyl) ethane, 1,4-bis (trimethoxy) Silyl) benzene, 1,4-bis (triethoxysilyl)
A compound such as benzene may be used.

In addition to the above-mentioned alkylsilazanes and alkylalkoxysilanes, compounds in which the alkylsilyl group is generally substituted with active hydrogen to bond with an acid are preferable because they easily react with the silanol group to be deactivated. Used.
Examples of the alkylsilyl group of this type of compound include a trimethylsilyl group, a triethylsilyl group, a tri-normalpropylsilyl group, a tri-isopropylsilyl group, a tri-normalbutyl group, a tri-isobutyl group, a tri-tert-butylsilyl group, and a tri-tributylsilyl group. -Normal octyl group, dimethylethylsilyl group, triphenyl group, diphenylmethylsilyl group and the like.

Of the compounds of this form, those having a trimethyl group as an alkylsilyl group are preferable examples of trimethylsilyl chloride, trimethylsilyl bromide, trimethylsilyl iodide, trimethylsilyl fluoride, trimethylsilyl acetate, trimethylsilyl bromoacetate, trimethylsilyl chloroacetate, Examples thereof include trimethylsilyl trichloroacetate, trimethylsilyl trifluoroacetate, trimethylsilyl chlorosulfonate, trimethylsilylbenzene sulfonate, trimethylsilylmethane sulfonate, trimethylsilyltrifluoromethane sulfonate, and the like.

Of these, silazane compounds and alkoxysilanes having two or three alkyl groups directly bonded to silicon atoms are particularly preferable. The surface treatment method using the above-mentioned alkylsilazane or alkylsilane compound after the film formation is carried out by a method such as coating, dipping or steam exposure.
Further, the treatment can be performed more easily by drying the film under heating and / or under vacuum prior to the reaction. The treatment of the silazane or silane compound varies depending on the treatment method, but is usually performed at 0 ° C. to 400 ° C. for several seconds to 48 hours. It is preferably several minutes to 5 hours.

The amount of silazane or silane compound used for these treatments varies depending on the method of the surface treatment process and the construction of the apparatus, but is preferably 10 times or more the film volume calculated from the film thickness and area of the thin film. When the amount of silazane or silane compound is less than 10 times, the coupling reaction with silanol in the thin film does not proceed sufficiently. When the silazane or silane compound is solid, it can be used by dissolving it in a solvent soluble in the compound.

The treatment can be carried out more completely by heating the membrane after bringing the membrane into contact with the silazane or silane compound by these treatments. The heat treatment is usually performed at 50 ° C. to 400 ° C. for several seconds to 48 hours. It is preferably several minutes to 5 hours. At this time, the heat treatment is preferably performed in a non-oxidizing atmosphere of nitrogen, argon, helium, hydrogen and a mixed gas thereof. The chemical treatment with the alkylsilazane or the alkylsilane compound and the subsequent heat treatment can be repeated to further reduce the silanol group density.

By using the porous silica thin film of the present invention obtained through the above manufacturing steps, it is possible to form a multilayer wiring insulating film for LSI, which has a high mechanical strength and a sufficiently low dielectric constant. The relative dielectric constant of the porous silica thin film of the present invention is
2.8 to 1.2 can be achieved under the above manufacturing conditions. This relative dielectric constant can be adjusted by the degree of pores in the porous silica thin film. That is, it means that it can be adjusted by the content of the organic polymer component in the coating composition of the present invention.

In the porous thin film of the present invention, BJH
In the pore distribution measurement by the method, pores with a diameter of 20 nm or more are not substantially recognized, and they are 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.

The porous silica thin film obtained by the present invention is a bulk porous silica body other than the thin film, such as an antireflection film, an optical film for an optical waveguide, a catalyst carrier, a heat insulating material, an absorbent, a column. Fillers, anti-caking agents, thickeners, pigments, opacifiers, ceramics, smoke suppressants,
It is also possible to use it as an abrasive, a dentifrice, etc.

[0089]

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. The porous silica thin film was evaluated by the following methods. (1) X-ray scattering measurement It was measured with RINT 2500 manufactured by Rigaku Denki. Measurement conditions are: divergence slit: 1/6 °, scattering slit: 1/6 °, light receiving slit:
A graphite monochromator was set in front of the detector (scintillation counter) at 0.15 mm. Tube voltage and tube current were measured at 40kV and 50mA, respectively, but can be varied as needed. The goniometer scanning method is 2
In the θ / θ scanning method, the scanning step was 0.02 °. As the sample, a thin film formed on a substrate having a size of about 2 cm × 2 cm was used.

(2) Hardness, Young's Modulus MTS Systems Corporation Nano Indenter DCM
It was measured at. The measuring method is as follows: A Berkovich type diamond indenter is used to form a film having a thickness of 0.7 μm to 1 μm on the substrate.
The load-displacement curve was obtained by pushing into the thin film of No. 3 and applying a load until it reached a certain load, and then removing it and monitoring the displacement. The surface has a contact stiffness of 200 N / m
Recognized under the condition. 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.

[0091]

[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, νi = 0.07, Ei = 11141G
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. (3) Relative permittivity It was measured using an SSM495 type automatic mercury CV measuring device manufactured by Solid State Measurement.

(4) Area Density of Silanol Group When the density of the porous silica thin film is ρ, the film thickness is t, and the area of the absorption peak due to Si—OH near 955 cm ⁻¹ in infrared absorption measurement is S , Area density of silanol groups (D)
Was calculated by the following formula. D = {S / (ρt)} × 100 (%) Here, the unit of ρ is g / cm ³ , the unit of t is μm, and the unit of S is the absorbance in the infrared absorption measurement. Here, the density and the film thickness of the thin film are measured by using an X-ray diffractometer ATX-G manufactured by Rigaku Denki Co., Ltd., and the X-ray is incident on the wafer on which the porous silica thin film is formed at a minute angle, and the total X-ray It was calculated by the critical angle of reflection and the vibration period of the X-ray reflectance intensity. For details of this method, see, for example, the literature (Shinya Matsuno et al., Advances in X-ray analysis, Volume 30, 1999,
P. 189-203).

(5) Crosslinking Ratio The crosslinking ratio of the porous silica thin film of the present invention is such that the Si atom is oxygen and the bond number obtained by multiplying the number of moles of all Si atoms contained in the thin film by the maximum valence of 4. It is defined as the ratio of the number of bonds bonded to the Si atom via an alkylene group or the like. The crosslinking rate in the thin film can be determined from the area of the signal by ²⁹ Si-NMR. As an example, a method of calculating the cross-linking rate of the thin film when tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) are used as the alkoxysilane will be described. Device: BRUKER (MSL-400) Observation nucleus: Si Observation frequency: 79.496 MHz Observation mode: hpdec Number of integrations: 1118 Sample tube: 7 mmφ Pulse width: 5.5 μs Waiting time: 60 seconds Measurement temperature: Chemical shift at room temperature Standard: Talc

Using the numerical values obtained from the above measuring apparatus and measuring conditions, the crosslinking rate is calculated by the following formula. Crosslinking rate (%) = 100 × {(T1 + 2 × T2 + 3 × T
3 + 4 × T4) + (M1 + 2 × M2 + 3 × M3)} /
{4 × (T0 + T1 + T2 + T3 + T4) + 4 × (M0
+ M1 + M2 + M3)} (In the formula, T0 and M0 are TE of the raw material in each of the above devices.
Indicated is the signal integral intensity attributed to a compound in which an ethoxy group in OS and MTES is at least partially hydrolyzed to become a hydroxyl group, and T1 and M1 are TEOS and MTE.
One point of each Si of S represents an integrated intensity of a signal attributed to a group formed by bonding to an adjacent Si atom through an oxygen atom, and T2 and M2 are two points of each Si in TEOS and MTES. Represents the integrated intensity of a signal attributed to a group formed by bonding an adjacent Si atom through an oxygen atom, and T3 and M3 represent TEOS and S of MTES, respectively.
i represents the integrated intensity of a signal attributed to a group formed by bonding three Si atoms to adjacent Si atoms via oxygen atoms, and T4 represents four Si atoms in TEOS adjacent Si atoms and oxygen atoms. Represents the integrated intensity of the signal attributed to the group formed by binding via).

[0096]

Example 1 5.85 g of tetraethoxysilane, 0.50 g of methyltriethoxysilane and a number average molecular weight of 640
1.50 g of polyethylene glycol polypropylene glycol polyethylene glycol block copolymer (number average molecular weight of polypropylene glycol part is 3200) of 0, 6.08 g of water, 8.84 g of ethanol and 1.24 g of 0.1N nitric acid were mixed at 35 ° C. After reacting for 4 hours at 60 ° C., 60% of the solution weight was distilled off under reduced pressure at 50 ° C. using a rotary evaporator, and 9.21 g of propylene glycol methyl ether was added to adjust the silica solid content to adjust the coating composition of the present invention. I got a thing.

3 ml of the obtained coating composition was dropped on a 6-inch silicon wafer and spin-coated at 1050 rpm for 60 seconds. Then, in air at 120 ° C. for 1 minute, under nitrogen atmosphere at 200 ° C. for 1 hour, and then under nitrogen atmosphere at 40 ° C.
The porous silica thin film having a thickness of 0.87 μm was obtained by firing at 0 ° C. for 1 hour. 2 ml of hexamethyldisilazane was dropped onto the porous silica thin film thus obtained on the wafer, and 1
Spin coating at 050 rpm for 60 seconds, under nitrogen atmosphere 2
1 hour at 00 ° C, then 1 hour at 400 ° C under nitrogen atmosphere
Heated for hours.

As a result of X-ray scattering measurement of the obtained thin film, clear scattering peaks were observed at scattering angles (2θ) of 0.98 ° and 1.80 °. The cross-linking ratio in the thin film is 88.
%, The relative dielectric constant at 1 MHz is 2.4, and
It was well below the dielectric constant of 4.5 of ₂ . The surface density of silanol groups is less than 0.3% and the hardness is 0.9G
Pa and Young's modulus were 8.1 GPa.

[0099]

Example 2 The porous silica thin film obtained in the first half of Example 1 was treated in the same manner except that hexamethylcyclotrisilazane was used in place of hexamethylcyclotrisilazane to obtain a film thickness of 0.84 μm. To obtain a porous silica coating film. As a result of X-ray scattering measurement of the obtained thin film, clear scattering peaks were observed at scattering angles (2θ) of 0.98 ° and 1.80 °, and the crosslinking rate in the thin film was 88%. The relative dielectric constant was 2.4, the areal density of silanol groups was less than 0.3%, the hardness was 1.0 GPa, and the Young's modulus was 8.8 GPa. Compared with Example 1, the hardness and Young's modulus tended to increase.

[0100]

Example 3 In Example 1, tetraethoxysilane was added to 5.
Example 1 was repeated except that 20 g was mixed with 1.25 g of trimethylethoxysilane and 1.125 g of polyethylene glycol polypropylene glycol polyethylene glycol block copolymer having a number average molecular weight of 6400 (the number average molecular weight of polypropylene oxide portion was 3200). By the same operation as above, a porous silica coating film having a thickness of 0.71 μm was obtained, and treated with hexamethyldisilazane and then heated in the same manner as in Example 1 to obtain a porous silica thin film.

As a result of X-ray scattering measurement of the obtained thin film, clear scattering peaks were observed at scattering angles (2θ) of 1.2 ° and 2.1 °. The measurement result is shown in FIG. The cross-linking rate in the thin film was 86%, the relative dielectric constant was 2.3, the surface density of silanol groups was less than 0.1%, the hardness was 1.2 GPa, and the Young's modulus was 10.3 GPa.

[0102]

Comparative Example 1 The same operation as in Example 3 was carried out except that the post-treatment with the silane coupling agent was not performed in Example 3.
A thin film of this comparative example was obtained. As a result of X-ray scattering measurement of the obtained thin film, clear scattering peaks were observed at scattering angles (2θ) of 1.0 ° and 1.9 °, a film thickness of 0.78 μm, and a crosslinking rate of 86.
%, The area density of silanol groups was 3.2%, and the relative dielectric constant was as large as 3.2, which was found to be unsuitable as an insulating thin film.

[0103]

Comparative Example 2 A membrane was obtained by the same procedure as in Example 3 except that polyethylene glycol (number average molecular weight was 1000) was used as the organic polymer in Example 3, and then the same post-treatment was carried out. As a result of X-ray scattering measurement of the obtained thin film, the intensity was a curve decreasing monotonously, and no peak was observed. The surface density of silanol exceeds 2%,
The relative permittivity was 3.5, which proved to be unsuitable as an insulating thin film for copper wiring.

[0104]

Example 4 The same procedure as in Example 1 was repeated except that 0.38 g of diethoxydimethylsilane was used instead of methyltriethoxysilane in the first half of Example 1, and the film thickness was 0.97 μm. To obtain a porous silica coating film. This coating film was spin-coated and heat-treated by the same operation except that hexamethyldisilazane in Example 1 was replaced with dimethylaminotrimethylsilane.

As a result of X-ray scattering measurement of the obtained thin film, clear scattering peaks were observed at the scattering angles (2θ) of 1.2 ° and 2.4 °, the crosslink density was 86%, and the relative dielectric constant was 2.4. Met. The areal density of silanol groups was less than 0.2%, the hardness was 1.0 GPa, and the Young's modulus was 8.5 GPa.

[0106]

Comparative Example 3 In the first half of Example 1, tetraethoxysilane was 1.67 g and methyltriethoxysilane was 3.55 g.
A porous silica coating film having a thickness of 0.77 μm was obtained by the same operation as in Example 1 except that the above was mixed and used. As a result of X-ray scattering measurement of the obtained thin film, almost no scattering peak was observed. The crosslink density was 57% and the relative dielectric constant was 2.4. The surface density of silanol groups was less than 0.2%, but the hardness was low at 0.5 GPa and the Young's modulus was low at 3.5 GPa.

[0107]

Example 5 A porous silica coating film was obtained by the same procedure except that hexamethylcyclotrisilazane was used instead of dimethylaminotrimethoxysilane in the latter half of Example 4. As a result of X-ray scattering measurement of the obtained thin film, clear scattering peaks were observed at scattering angles (2θ) of 1.2 ° and 2.4 °, the crosslink density was 86%, and the silanol group areal density was 0.2.
%, The hardness was 1.1 GPa and the Young's modulus was 8.8 GPa.

[0108]

Example 6 A porous silica coating film was obtained by the same procedure except that hexamethyldisilazane was used instead of dimethylaminotrimethoxysilane in the latter half of Example 4. As a result of X-ray scattering measurement of the obtained thin film, the scattering angle (2
θ) has clear scattering peaks at 1.2 ° and 2.4 °, the crosslink density is 86%, the surface density of silanol groups is less than 0.2%, the hardness is 1.1 GPa, and the Young's modulus is 8.4 G.
It was Pa.

[0109]

The porous silica thin film according to the present invention has a sufficiently low relative dielectric constant and is stable and can withstand a CMP process in a copper wiring process of a semiconductor device sufficiently. As is the best.

[Brief description of drawings]

FIG. 1 is a chart of X-ray scattering measurement of the thin film of Example 3.

Continued front page    F term (reference) 4G072 AA25 BB09 BB15 FF04 FF06                       GG01 GG03 HH28 HH30 JJ11                       JJ47 KK01 LL13 LL15 MM01                       NN21 PP17 QQ06 RR05 RR07                       RR12 UU01 UU07 UU17 UU21                       UU22 UU30                 5F033 GG01 GG02 HH04 HH07 HH08                       HH11 HH13 HH14 HH17 HH18                       HH19 HH21 QQ48 QQ74 RR01                       RR03 RR04 RR05 RR06 RR09                       RR11 RR13 RR14 RR15 RR22                       RR25 RR29 SS03 SS22 TT04                       WW00 WW04 XX03 XX12 XX24                 5F058 AA10 AC05 AF04 AG01 AH02

Claims (3)

[Claims] 1. The cross-linking ratio of the porous silica thin film is 70% or more, and the X-ray scattering measurement of the porous silica thin film has at least one scattering angle (2θ) within the range of 0.5 to 3 °. And a surface density of silanol groups of the porous silica thin film is 2% or less. 2. A multilayer wiring structure including a plurality of insulating layers and wirings formed thereon, wherein at least one layer of the insulating layers is composed of the porous silica thin film according to claim 1. A multi-layer wiring structure characterized by the following. 3. A semiconductor device including the multilayer wiring structure according to claim 2.