Surface composition and distribution of fluorine in plasma-fluorinated polyimide

Abstract

Surface composition, fluorine distribution, and morphology were determined for polyimide films modified downstream from microwave plasmas containing CF4/O2. Complementary analytical techniques including x-ray photoelectron spectroscopy, Rutherford backscattering spectroscopy, and scanning electron microscopy yielded a more complete understanding of polyimide fluorination and subsequent etching of the modified film. Depth of fluorination increased nonlinearly with treatment time for films exposed downstream from a CF4-rich plasma. Exposure downstream from an O2-rich plasma resulted in a reduction of thickness in both the fluorinated layer and the unmodified polyimide during etching. Finally, a model for fluorination of polyimide and subsequent removal is proposed.