Low-dielectric, nanoporous organosilicate films prepared via inorganic/organic polymer hybrid templates

Dielectric insulator materials containing nanometer-scale closed-cell pores with low dielectric constants (k < 2.2), good mechanical properties, and high dielectric breakdown strengths are required for future semiconductor devices. In this paper we present a novel method for preparing nanoporous polyorganosilicate films, which promise to satisfy the key requirements, via inorganic/organic polymer hybrid templating. The nanometer-scale inorganic/organic polymer hybrids are generated in situ upon heating mixtures of methylsilsesquioxane (MSSQ) prepolymer with star-shaped hydroxy-terminated poly(epsilon-caprolactone) (PCL) to similar to 250 degrees C, causing chain extension and cross-linking of MSSQ. Subsequent heating to 430 degrees C results in the thermal decomposition and volatilization of PCL components from the vitrified poly(methylsilsesquioxane) (PMSSQ) matrix;, leaving behind porous PMSSQ films with pores with the size and shape of the original hybrid morphology. A dielectric constant as low as 2.1 has been achieved for closed-cell nanoporous PMSSQ films with hydrophobic surfaces and excellent breakdown strengths close to that of SiO2. Moreover, conductance measurements on inorganic/organic polymer hybrids offer insight into the development of interconnected PCL domains as the PCL content is increased above similar to 25%.