Etching and film formation in CF3Br plasmas: some qualitative observations and their general implications

CF3Br plasma discharges exhibit a number of unusual phenomena. Under some conditions silicon and SiO2 can be concurrently etched, while in other circumstances only SiO2 is etched and silicon is coated with a uniform, cross-linked fluorocarbon film. Single crystal n-doped silicon is etched more rapidly than undoped silicon. The fluorocarbon polymer overlays a monolayer of bromine at the silicon interface, but negligible bromine is incorporated into the fluorocarbon. Some chemical mechanisms which account for these observations are presented.