CHF3–O2 reactive ion etching of 4H-SiC and the role of oxygen

Reactive ion etching of 4H-SiC was performed using a CHF3–O2 plasma. The etch rate and mean surface roughness were investigated as a function of the ratio of the O2 flow rate to the total gas flow rate. It was found that oxygen plays an indirect role in contributing to the etching of SiC. An optimum O2 fraction of 20% was found to give a maximum etch rate of 35 nm/min. On the other hand, the root-mean-square (RMS) surface roughness was found to increase from 1.31 to 2.34 nm when the O2 fraction increased from 0% to 80%. Auger electron spectroscopy results for the samples etched at the optimum condition of 20% O2 fraction revealed the presence of oxygen on the etched surface in a form of an oxide-like layer (SiOx). No carbon residue (carbon rich-layer) and aluminum were found. Based on our results, the role of O2 in the reactive ion etching of 4H-SiC will be presented.