The need for low dielectric constant materials with k < 2 for devices with feature sizes below 130 nm has generated interest to develop a variety of nanoporous materials. One such class is the organic/inorganic hybrid films where nanopores are formed/incorporated by thermal decomposition of porogens in organosilicate matrix at high temperatures up to 430oC. Our process is selective extraction of different types of porogens in organic matrix like methylsilsesquioxane (MSSQ) via supercritical carbon dioxide (SCCO2). In contrast with thermal decomposition, we have demonstrated that SCCO2 extraction occurred at much lower temperature (160oC) and 6000 psi pressure. The present work will demonstrate SCCO2 extraction at lower temperatures and pressures. Introducing certain modifiers in the SCCO2 process can help attain this goal. Furthermore, a pulse or dynamic SCCO2 system will be utilized to reduce the extraction time drastically. Fourier transform infrared spectroscopy (FTIR) is extensively used to monitor the extraction process. The measured values of refractive index and dielectric constant and the calculated values of porosity will confirm the successful extraction of porogens using SCCO2.
J. A. Lubguban, Lahlouh, B., Biswas, N., Dr. T. Rajagopalan, and Gangopadhyay, S., “Selective Extraction of Porogens in Hybrid Films by Supercritical Carbon Dioxide”, in APS Meeting Abstracts, 2003.