Plasma copolymerization of tetrafluoroethylene/hexamethyldisiloxane and insitu Fourier transform infrared spectroscopy of its gas phase

Plasma copolymerization of hexamethyldisiloxane (HMDSO, (CH3)(3)-Si-O-Si-(C H3)(3)) and tetrafluoroethylene (CF2=CF2) was performed using an RF plasma enhanced chemical vapor deposition method, for its application to low diele ctric constant intermetal dielectrics. Film structure was investigated by X -ray photoelectron spectroscopy and Fourier transform infrared (FT-IR) spec troscopy. Film composition was controlled gradually from that of fluorinate d carbon to organic siloxane by changing the HMDSO mixing ratio. The films possessed a dielectric constant of less than 2.5 for an HMDSO mixing ratio of less than 10%. Thermal treatment of the films revealed that the C-F-n, S i-O-Si, Si-(CH3)(n) and Si-(CH2)(n)-Si bonds were stable to 400 degrees C, but the C-H-2 bonds were not. In situ gas-phase FT-IR spectroscopy was also performed on the plasma, and the reaction mechanisms are discussed.