Nanoporous organosilicate thin films prepared with covalently bonded adamantylphenol pore generators

A new class of nanoporous organosilicate thin films with balanced mechanical and low dielectric properties has been designed and prepared using covalently bonded adamantylphenols as pore-generating (porogen) materials. The adamantylphenol groups were grafted or bridged to poly(methyl silsesquioxane) (PMSSQ) polymers through propyl linkers and the thermal decomposition of such porogens through the cleavage of covalent bonds during curing was confirmed by FT-IR, TGA, and GC-MS. One of the nanoporous thin films examined in this study contains nanopores, less than 10 nm, within the films with 18% porosity, as characterized by X-ray reflectivity, ellipsometry, and nitrogen sorption analysis. Elastic modulus of a nanoporous film measured by a nanoindenter was significantly increased to 5.5 GPa, while maintaining the dielectric constant of 2.3, which is due to the partial formation of silica structure by the decomposition of residual propenyl groups after the bond cleavage of porogens and also due to the enhanced cross-linking density in the case of bridge-PMSSQ.