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Sol-Gel Processing of Low Dielectric Constant Nanoporous Silica Thin Films

Published online by Cambridge University Press:  15 March 2011

Deok-Yang Kim
Affiliation:
Department of Chemical, Biochemical, and Materials Engineering, Stevens Institute of Technology, Hoboken, NJ 07030, U.S.A.
Henry Du
Affiliation:
Department of Chemical, Biochemical, and Materials Engineering, Stevens Institute of Technology, Hoboken, NJ 07030, U.S.A.
Suhas Bhandarkar
Affiliation:
Bell Laboratories, Lucent Technologies, Murray Hill, NJ 07974, U.S.A.
David W. Johnson Jr
Affiliation:
Agere Systems, Murray Hill, NJ 07974, U.S.A.
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Abstract

Tetramethyl ammonium silicate (TMAS) is known as a structuring agent in zeolite synthesis. We report its first use to prepare porous silica films for low k dielectric applications in microelectronics. A solution of TMAS 18.7 wt. % was spin coated on silicon substrates with a 3000 Å thick thermal oxide. The spin coated films were subsequently heat-treated at 450°C to obtain porous silica. The use of TMAS solution without gelation led to films of only moderate porosity value of 10%. The addition of methyl lactate, a gelling agent, significantly increased film porosity and improved the pore size distribution. For example, 50% porosity and uniform pore size distribution (average pore size ∼ 40 Å) has been achieved. Dielectric constants (k) of our porous films are as low as 2.5.

Type
Research Article
Copyright
Copyright © Materials Research Society 2002

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References

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