Study of the reactive ion etching of 6H-SiC and 4H-SiC in SF6/Ar plasmas by optical emission spectroscopy and laser interferometry

Optical emission spectroscopy (OES) and laser interferometry (LI) were investigated as monitoring methods during reactive ion etching (RIE) of hexagonal SiC in SF6/Ar gas mixtures. The etch rate and the surface roughness were monitored by LI, while at the same time OES monitored the intensity of the fluorine-related 704 nm line. It was found that the etch rate is directly related to the above intensity and not to the self-induced DC-bias. This explains the very high etch rates obtained at high pressures (150-250 mTorr) despite the low DC-bias values (similar to100 V). Etch rates higher than 400 nm/min were achieved for 400 W of rf power. (C) 2002 Elsevier Science Ltd. All rights reserved.