Synthesis of poly(methyl-co-trifluoropropyl)-silsesquioxanes and their thin films for low dielectric application

Poly(methyl-co-trifluropropyl)silsesquioxanes (P(M-co-TFP)SSQs) were prepared using methyltrimethoxysilane (MTMS) and trifluoropropyltrimethoxysilane (TFPTMS). The molecular weight, microstructure of the copolymers and properties of their thin films have been changed by adjusting reaction parameters such as the molar ratio of water to silane, the molar ratio of catalyst to silane, reaction time, solvent content, and temperature. The refractive index of the copolymer thin film decreased from 1,404 to ca. 1.348 as curing temperature was increased to 420degreesC. The dielectric constant of the film decreased with an increase of the molecular weight of the copolymer, and the lowest dielectric constant obtained was ca 2.2. Hardness and elastic modulus of the thin films were 0.7 and 5 GPa, respectively Crack velocity was measured to be 10(-11) m/s at the film thickness of around 0.9 mum under aqueous environment.