Supercritical CO2 Extraction of Porogen Phase: An Alternative Route to Nanoporous Dielectrics
- SLAC
We present a supercritical CO{sub 2} (SCCO{sub 2}) process for the preparation of nanoporous organosilicate thin films for ultra low dielectric constant materials. The porous structure was generated by SCCO{sub 2} 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 ca. 450 C) and by a SCCO{sub 2} process for 25 wt% and 55 wt% porogen loadings were evaluated. It is found that the SCCO{sub 2} 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.
- Research Organization:
- Stanford Linear Accelerator Center (SLAC), Menlo Park, CA
- Sponsoring Organization:
- SC
- DOE Contract Number:
- AC02-76SF00515
- OSTI ID:
- 839790
- Report Number(s):
- SLAC-PUB-10846
- Country of Publication:
- United States
- Language:
- English
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