Chemistry of Materials

Structure and interaction of organic/inorganic hybrid nanocomposites for microelectronic applications. 1. MSSQ/P(MMA-co-DMAEMA) nanocomposites

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Nanoporous methyl silsesquioxane (MSSQ), which is an important and promising candidate for spin-on ultralow dielectric constant applications, has been produced via the thermosetting of MSSQ, templated by a nanodispersed, thermally decomposable pore generator (porogen)-poly(methyl methacrylate-co-dimethylaminoethyl methacrylate) [P(MMA-co-DMAEMA)]. Fourier transform infrared spectroscopy is used to study the interaction and structural changes of MSSQ/P(MMA-co-DMAEMA) nanocomposites as a function of curing temperature (ranging from 25 to 450°C) and porogen loading (ranging from 0 to 70 wt %). We find that strong hydrogen-bonding interactions occur between the -OH end groups in MSSQ and the tertiary amino groups in P(MMA-co-DMAEMA) in films at 25°C. An increase in cure temperature from 25 to 250°C and finally to 450°C transforms MSSQ from a material with many reactive end groups to a highly cross-linked structure. In addition, the amino substituent in P(MMA-co-DMAEMA) can act as a catalyst for the condensation and cross-linking of MSSQ. An increase of porogen loading to 70 wt % and a decrease in the silanol group concentration in MSSQ both hinder the formation of the -Si-O-Si- network. Finally, small-angle x-ray scattering (SAXS) results indicate that MSSQ resins initially having higher -OH end group concentrations ultimately generate smaller pores after the removal of porogens.