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Supercritical CO2 extraction of porogen phase: An alternative route to nanoporous dielectrics

Published online by Cambridge University Press:  01 November 2004

J.A. Lubguban ,
S. Gangopadhyay ,
B. Lahlouh ,
T. Rajagopalan ,
N. Biswas ,
J. Sun ,
D.H. Huang ,
S.L. Simon ,
A. Mallikarjunan  and
H-C. Kim
...Show all authors
J.A. Lubguban
Affiliation:
Department of Electrical and Computer Engineering, University of Missouri, Columbia, Missouri 65211
S. Gangopadhyay*
Affiliation:
Department of Electrical and Computer Engineering, University of Missouri, Columbia, Missouri 65211
B. Lahlouh
Affiliation:
Physics Department, Texas Tech University, Lubbock, Texas 79409
T. Rajagopalan
Affiliation:
Physics Department, Texas Tech University, Lubbock, Texas 79409
N. Biswas
Affiliation:
Physics Department, Texas Tech University, Lubbock, Texas 79409
J. Sun
Affiliation:
Chemical Engineering Department, Texas Tech University, Lubbock, Texas 79409
D.H. Huang
Affiliation:
Chemical Engineering Department, Texas Tech University, Lubbock, Texas 79409
S.L. Simon
Affiliation:
Chemical Engineering Department, Texas Tech University, Lubbock, Texas 79409
A. Mallikarjunan
Affiliation:
Center for Integrated Electronics, Rensselaer Polytechnic Institute, Troy, New York 12180
H-C. Kim
Affiliation:
IBM Almaden Research Center, San Jose, California 95120
J. Hedstrom
Affiliation:
IBM Almaden Research Center, San Jose, California 95120
W. Volksen
Affiliation:
IBM Almaden Research Center, San Jose, California 95120
R.D. Miller
Affiliation:
IBM Almaden Research Center, San Jose, California 95120
M.F. Toney
Affiliation:
SSRL, Stanford Linear Accelerator Center, Menlo Park, California 94025
*
a)Address all correspondence to this author. e-mail:gangopadhyays@missouri.edu
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Abstract

We present a supercritical CO2 (SCCO2) process for the preparation of nanoporous organosilicate thin films for ultralow dielectric constant materials. The porous structure was generated by SCCO2 extraction of a sacrificial poly(propylene glycol) (PPG) from a nanohybrid film, where the nanoscopic domains of PPG porogen are entrapped within the crosslinked poly(methylsilsesquioxane) (PMSSQ) matrix. As a comparison, porous structures generated by both the usual thermal decomposition (at approximately 450 °C) and by a SCCO2 process for 25 and 55 wt% porogen loadings were evaluated. It is found that the SCCO2 process is effective in removing the porogen phase at relatively low temperatures (<200 °C) through diffusion of the supercritical fluid into the phase-separated nanohybrids and selective extraction of the porogen phase. Pore morphologies generated from the two methods are compared from representative three-dimensional (3D) images built from small-angle x-ray scattering (SAXS) data.

Keywords

PorosityThin filmDielectric
Type
Articles
Information
Journal of Materials Research , Volume 19 , Issue 11 , November 2004 , pp. 3224 - 3233
Copyright
Copyright © Materials Research Society 2004

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