Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-10-10
2001-08-07
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S077000, C521S086000, C521S088000, C521S154000, C438S624000, C438S781000
Reexamination Certificate
active
06271273
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to porous materials. In particular, this invention relates to the preparation and use of porous films containing organo polysilica materials and having a low dielectric constant.
As electronic devices become smaller, there is a continuing desire in the electronics industry to increase the circuit density in electronic components, e.g., integrated circuits, circuit boards, multichip modules, chip test devices, and the like without degrading electrical performance, e.g., crosstalk or capacitive coupling, and also to increase the speed of signal propagation in these components. One method of accomplishing these goals is to reduce the dielectric constant of the interlayer, or intermetal, insulating material used in the components. A method for reducing the dielectric constant of such interlayer, or intermetal, insulating material is to incorporate within the insulating film very small, uniformly dispersed pores or voids.
Porous dielectric matrix materials are well known in the art. One known process of making a porous dielectric involves co-polymerizing a thermally labile monomer with a dielectric monomer to form a block copolymer, followed by heating to decompose the thermally labile monomer unit. See, for example, U.S. Pat. No. 5,776,990. In this approach, the amount of the thermally labile monomer unit is limited to amounts less than about 30% by volume. If more than about 30% by volume of the thermally labile monomer is used, the resulting dielectric material has cylindrical or lamellar domains, instead of pores or voids, which lead to interconnected or collapsed structures upon removal, i.e., heating to degrade the thermally labile monomer unit. See, for example, Carter et. al., Polyimide Nanofoamsfrom Phase-Separated Block Copolymers,
Electrochemical Society Proceedings
, volume 97-8, pages 32-43 (1997).
Thus, the block copolymer approach provides only a limited reduction in the dielectric constant of the matrix material.
Another known process for preparing porous dielectric materials disperses thermally removable particles in a dielectric precursor, polymerizing the dielectric precursor without substantially removing the particles, followed by heating to substantially remove the particles, and, if needed, completing the curing of the dielectric material. See, for example, U.S. Pat. No. 5,700,844. In the '844 patent, uniform pore sizes of 0.5 to 20 microns are achieved. However, this methodology is unsuitable for such electronic devices as integrated circuits where feature sizes are expected to go below 0.25 microns.
U.S. patent application Ser. No. 09/460,326 (Allen et al.), discloses porogen particles that are substantially compatibilized with B-staged dielectric matrix materials. However, this patent application does not broadly teach how to prepare porous dielectric layers containing organo polysilica materials.
U.S. Pat. No. 5,895,263 (Carter et al.) discloses a process for manufacturing an integrated circuit device containing an organo polysilica porous dielectric layer. In this patent, the porous organo polysilica layer was prepared by incorporating a decomposable polymer. A long list of decomposable polymers is disclosed, including cross-linked, insoluble nanospheres. The '263 patent does not disclose how to prepare such nanospheres nor how to compatibilize such nanospheres with the organo polysilica dielectric matrices.
Other methods of preparing porous dielectric materials are known, but suffer from broad distributions of pore sizes, too large pore size, such as greater than 20 microns, or technologies that are too expensive for commercial use, such as liquid extractions under supercritical conditions.
There is thus a need for improved porous organo polysilica dielectric matrix materials with substantially smaller pore sizes and a greater percent by volume of pores for use in electronic components, and in particular, as an interlayer, or intermetal, dielectric material for use in the fabrication of integrated circuits.
SUMMARY OF THE INVENTION
It has now been surprisingly found that certain polymeric particles (or porogens) incorporated into an organo polysilica dielectric matrix provide porous films having a suitable dielectric constant and sufficiently small pore size for use as insulating material in electronic devices such as integrated circuits and printed wiring boards. Such polymeric particles provide organo polysilica dielectric matrix material having a greater percentage of pores by volume than is available from known porogens.
In a first aspect, the present invention is directed to a method of preparing porous organo polysilica dielectric materials including the steps of: a) dispersing removable polymeric porogen in a B-staged organo polysilica dielectric material; b) curing the B-staged organo polysilica dielectric material to form an organo polysilica dielectric matrix material without substantially degrading the porogen; and c) subjecting the organo polysilica dielectric matrix material to conditions which at least partially remove the porogen to form a porous organo polysilica dielectric material without substantially degrading the organo polysilica dielectric material; wherein the porogen is substantially compatible with the B-staged organo polysilica dielectric material and wherein the porogen includes as polymerized units at least one compound selected from silyl containing monomers or poly(alkylene oxide) monomers; provided that when the organo polysilica is methyl silsesquioxane and the porogen comprises (trimethoxylsilyl)propylmethacrylate as polymerized units, the porogen further includes as polymerized units at least one other compound selected from silyl containing monomers or poly(alkylene oxide) monomers.
In a second aspect, the present invention is directed to porous organo polysilica dielectric matrix materials prepared by the method described above.
In a third aspect, the present invention is directed to a method of preparing an integrated circuit including the steps of: a) depositing on a substrate a layer of a composition including B-staged organo polysilica dielectric material having polymeric porogen dispersed therein; b) curing the B-staged organo polysilica dielectric material to form an organo polysilica dielectric matrix material without substantially removing the porogen; c) subjecting the organo polysilica dielectric matrix material to conditions which at least partially remove the porogen to form a porous organo polysilica dielectric material layer without substantially degrading the organo polysilica dielectric material; d) patterning the organo polysilica dielectric layer; e) depositing a metallic film onto the patterned organo polysilica dielectric layer; and f) planarizing the film to form an integrated circuit; wherein the porogen is substantially compatible with the B-staged organo polysilica dielectric material and wherein the porogen includes as polymerized units at least one compound selected from silyl containing monomers or poly(alkylene oxide) monomers; provided that when the otgano polysilica is methyl silsesquioxane and the porogen includes (trimethoxylsilyl)propylmethacrylate as polymerized units, the porogen further includes as polymerized units at least one other compound selected from silyl containing monomers or poly(alkylene oxide) monomers.
In a fourth aspect, the present invention is directed to an integrated circuit prepared by the method described above.
In a fifth aspect, the present invention is directed to a composition including a B-staged organo polysilica dielectric material and a polymeric porogen, wherein the porogen is substantially compatible with the B-staged organo polysilica dielectric material and wherein the porogen includes as polymerized units at least one compound selected from silyl containing monomers or poly(alkylene oxide) monomers; provided that when the organo polysilica is methyl silsesquioxane and the porogen includes (trimethoxylsilyl)propylmethacrylate as polymerized units, the porogen further includes a
Annan Nikoi
Gallagher Michael K.
Gore Robert H.
Lamola Angelo A.
You Yujian
Bagwell Melanie
Cairns S. Matthew
Gorr Rachel
Shipley Company L.L.C.
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