REACTIVE ION ETCHING CHARACTERIZATION OF A-SIC-H IN CF4 O-2 PLASMA/

In this paper a reactive ion etching process on amorphous silicon carb ide (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 c omposition was analyzed by electron microprobe analysis. The effect of hydrogen presence in the deposition chamber and of the material dopin g on the etch rate was considered. The etch rate in a CF4/O-2 plasma w as investigated as a function of the r.f. power and gas pressure in th e etching chamber, taking the loading effect also into account. An app reciable induction time was observed only for pure a-Si. The etch rate , increased in carbon-rich films, was found to be almost linearly rela ted 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 va lue in the range 30-60 mTor, after which it decreases. However, no dec rease at higher pressure was seen for the a-Si:H films.