Formation of a silicon-carbide layer during CF4/H2 dry etching of Si

Silicon specimens which had been reactive ion etched in CF4/x% H2 (0≤x≤40) have been characterized by x-ray photoelectron emission spectroscopy. Angular rotation was used to study films deposited by the plasma process onto the Si surface. In agreement with previous studies it is found that plasma exposure of Si specimens leads to the deposition of a fluorocarbon film. An intriguing new finding was the discovery of a silicon-carbide layer localized near the fluorocarbon-film/Si interface. The existence of this carbide layer was found to be independent of gas composition from 0–40% H2 for a 1-min plasma exposure.