Reactive ion etching characterization of a-SiC: H in CF4/O2 plasma

In this paper a reactive ion etching process on amorphous silicon carbide (a-SiC) films is characterized by varying the carbon content from 0.73 molar fraction of C (X(c)=0.73) to X(c)=0 (pure a-Si). The film composition was analyzed by electron microprobe analysis. The effect of hydrogen presence in the deposition chamber and of the material doping on the etch rate was considered. The etch rate in a CF4/O-2 plasma was investigated as a function of the r.f. power and gas pressure in the etching chamber, taking the loading effect also into account.An appreciable induction time was observed only for pure a-Si. The etch rate, increased in carbon-rich films, was found to be almost linearly related to the optical energy gap of the material. However, the etch rate was not a consistent function of X(c). An analytical relation between etching rate and r.f. power is proposed. Varying the gas pressure, and a-SiC etch rate slowly rises, remains nearly constant at a maximum value in the range 30-60 mTor, after which it decreases. However, no decrease at higher pressure was seen for the a-Si:H films.