NER: Supercritical Carbon Dioxide Extraction Process for Forming Nanoporous Materials for Low-k and Biosensor Applications

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Materials with controlled nanoporous structures will be developed for potential applications in the areas of microelectronics and biosensors. The goal is to couple a nanotemplating methodology for creating nanophase separated materials with supercritical CO2 extraction of one of the phases. The advancement of the proposed methodology over the current state of the art includes increased flexibility in the types of matrix materials which can be used, as well as processing advantages over methods in which the porogen is removed from the matrix by thermal degradation. The scientific challenge of the proposed work lies in understanding the polymer physics associated with extraction of the CO2 soluble component without collapse of the matrix. In essence, this is related to the glass transition, plasticization effects, the viscoelastic properties of the matrix and the stresses incurred due to extraction. We will prepare spin-on films at Texas Tech, as well as working with collaborators at IBM, to prepare nanophase separated morphologies. The films will contain a component which is insoluble in supercritical CO2 and will also contain a soluble component which can be extracted. Characterization of the properties of the films before and after exposure to supercritical CO2 extraction will be performed, including measurement of the dielectric properties, thickness and refractive index. In addition, films will be studied by Fourier transform infrared spectrometry, transmission electron microscopy and atomic force microscopy. Two graduate students and one undergraduate researcher will perform the research under the direct supervision of the PIs.