Method for making microporous silicone resins with narrow...

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...

Reexamination Certificate

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C528S035000, C427S226000, C427S228000

Reexamination Certificate

active

06197913

ABSTRACT:

BACKGROUND OF INVENTION
The present invention relates generally to a method for making microporous silicone resins which are useful for forming low dielectric constant films. More specifically, the present invention is a method for making a microporous silicone resin having a narrow pore size range by hydrosilating a hydridosilicon containing resin with an alkenyltriarylsilane, coating the hydrosilated resin on a substrate, and heating the coated substrate in an inert atmosphere to effect thermolysis of the aryl substituents and their elimination from the coating as a gas.
Semiconductor devices often have one or more arrays of patterned interconnect levels that serve to electrically couple the individual circuit elements forming an integrated circuit (IC). These interconnect levels are typically separated by an insulating or dielectric film. Previously, a silicon oxide film formed using chemical vapor deposition (CVD) or plasma enhanced techniques (PECVD) was the most commonly used material for such dielectric films. However, as the size of circuit elements and the spaces between such elements decreases, the relatively high dielectric constant of such silicon oxide films is inadequate to provide adequate electrical insulation.
In order to provide a lower dielectric constant than that of silicon oxide, dielectric films formed from siloxane-based resins have found use. An example of such films are those formed from poly(hydrogen)silsesquioxane resins as described for example in Collins et al., U.S. Pat. No. 3,615,272 and Haluska et al. U.S. Pat. No. 4,756,977. While such films provide lower dielectric constants than CVD or PECVD silicon oxide films and also provide other benefits such as enhanced gap filling and surface planarization, typically the dielectric constants of such films are limited to approximately 3 or greater.
It is well known that the dielectric constant of the above discussed insulating films is an important factor where IC's with low power consumption, cross-talk, and signal delay are required. As IC dimensions continue to shrink, this factor increases in importance. As a result, siloxane based resin materials and methods for making such materials that can provide electrically insulating films with dielectric constants below 3 are desirable. In addition it is desirable to have siloxane-based resins and method for making such resins that provide low dielectric constant films which have a high resistance to cracking. Also, it is desirable for such siloxane-based resins to provide low dielectric constant films by standard processing techniques.
It is known that the dielectric constant of solid films decrease with a decrease in density of the film material. Therefore considerable work is being conduct to develop microporous insulating films for use on semiconductor devices.
Kapoor, U.S. Pat. No. 5,494,859, describes a low dielectric constant insulating layer for an integrated circuit structure and a method of making the layer. A porous layer is formed by depositing on a structure a composite layer comprising an insulating matrix material and a material which can be converted to a gas upon subjection to a converting process. Release of the gas leaves behind a porous matrix of the insulating material which has a lower dielectric constant than the composite layer. The matrix forming material is typically silicon oxide and the material which can be converted to a gas upon subjection to a converting process is exemplified by carbon.
Hedrick et al., U.S. Pat. No. 5,776,990, describe an insulating foamed polymer having a pore size less than about 100 nm made from a copolymer comprising a matrix polymer and a thermally decomposable polymer by heating the copolymer above the decomposition temperature of the decomposable polymer. The copolymers described are organic polymers that do not contain silicon atoms.
Smith et al., WO 98/49721, describe a process for forming a nanoporous dielectric coating on a substrate. The process comprises the steps of blending an alkoxysilane with a solvent composition and optional water; depositing the mixture onto a substrate while evaporating at least a portion of the solvent; placing the substrate in a sealed chamber and evacuating the chamber to a pressure below atmospheric pressure; exposing the substrate to water vapor at a pressure below atmospheric pressure and then exposing the substrate to base vapor.
Mikoshiba et al., Japanese Laid-Open Patent (HEI)
10-287746
, describe the preparation of porous films from siloxane-based resins having organic substituents which are oxidized at a temperature of 250° C. or higher. The useful organic substituents which can be oxidized at a temperature of 250° C. or higher given in this document include substituted and unsubstituted groups as exemplified by 3,3,3-trifluoropropyl, &bgr;-phenethyl group, t-butyl group, 2-cyanoethyl group, benzyl group, and vinyl group.
Mikoskiba et al., J Mat. Chem., 1999, 9, 591-598, report a method to fabricate angstrom size pores in poly (methylsilsesquioxane) films in order to decrease the density and the dielectric constant of the films. Copolymers bearing methyl(trisiloxysilyl) units and alkyl (trisiloxysilyl) units are spin-coated on to a substrate and heated at 250° C. to provide rigid siloxane matrices. The films are then heated at 450° C. to 500° C. to remove thermally labile groups and holes are left corresponding to the sized of the substituents. Trifluoropropyl, cyanoethyl, phenylethyl, and propyl groups were investigated as the thermally labile substituents.
SUMMARY OF INVENTION
The present invention is a method for preparing a microporous silicone resin which can be used to form low dielectric constant films useful for electrical insulating coatings on electronic devices. The method comprises (A) contacting a hydridosilicon containing resin with an alkenyltriarylsilane in the presence of a platinum group metal-containing hydrosilation catalyst effecting formation of a silicon resin where at least 5percent of silicon atoms are substituted with at least one triarylsilylalkylene group and at least 45 percent of silicon atoms are substituted with at least one hydrogen atom and (B) heating the silicon resin of step (A) in an inert atmosphere at a temperature sufficient to effect thermolysis of the triarylsilylalkylene groups from the silicon atoms.
DESCRIPTION OF INVENTION
The present invention is a method for preparing a microporous silicone resin which can be used to form low dielectric constant films useful for electrical insulating coatings on electronic devices. The method comprises
(A) contacting a hydridosilicon containing resin with an alkenyltriarylsilane described by formula
Ar
3
Si(CH
2
)
p-2
CH═CH
2
  (1)
 in the presence of a platinum group metal-containing hydrosilation catalyst effecting formation of a silicon resin where at least 5 percent of silicon atoms are substituted with at least one triarylsilylalkylene group described by formula
Ar
3
Si(CH
2
)
p-
  (2)
 and at least 45 percent of silicon atoms are substituted with at least one hydrogen atom and
(B) heating the silicon resin of step (A) in an inert atmosphere at a temperature sufficient to effect thermolysis of the triarylsilylalkylene groups from the silicon atoms; where each Ar is an independently selected aryl group and p=2 to 20.
The hydridosilicon containing resin can be any of those known in the art where at least 50 percent of the silicon atoms have a hydrogen substitution and as such can be homopolymers or copolymers. The following nonlimiting list of possible hydrolysates and co-hydrolysates are, however, specifically contemplated:
(HSiO
3/2
)
n
,
(H
2
SiO)
m
,
(HSiO
3/2
)x(R
1
SiO
3/2
)
y
,
(HSiO
3/2
)x(R
l
R
2
SiO)
y
,
(HSiO
3/2
)x(R
l
R
2
SiO)y(SiO
2
)z, and
(HSiO
3/2
)x(H
2
SiO)y;
where R
1
is a substituent which is not removed by heating at a temperature up to about 600° C., R
2
is either R
1
or hydrogen, n≧2, m≧3, the mole fractions of x, y, and z must total 1 in each of the copolymers, and x is at least 50 percent o

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