Low Dielectric Constant, High Temperature Stable Copolymer Thin Films by Room Temperature Chemical Vapor Deposition

ABSTRACTPolyxylylene thin films grown by the chemical vapor deposition (CVD) process have long been utilized to achieve uniform, pinhole-free conformal coatings. They have recently been cited as possible low dielectric constant films for intermetal layers in high-speed ICs. Homopolymer films are highly crystalline and have a glass transition temperature around room temperature. We have demonstrated that room temperature copolymerization with previously untested comonomers can be achieved during the CVD process. Copolymerizing chloro-p-xylylene with perfluorooctyl methacrylate results in the dielectric constant at optical frequencies being lowered from 2.68 to 2.19. Copolymerizing p-xylylene with vinylbiphenyl resulted in films which increase the temperature at which oxidative scission occurs from 320 to 450C. Copolymerizing p-xylylene with 9-vinylanthracene resulted in a brittle, yellow film.