Reactive ion etching of 6H-SiC in an ECR plasma of CF4-O2 mixtures using both Ni and Al masks

We report on the dry etching of 6H-SiC using a RF-biased electron cyclotron resonance plasma and a CF4-O2 mixture. We have investigated the etching rate dependency on the percentage of oxygen in the gas mixture, the total pressure and flow gas. We have found that using a gas mixture with 40% of O2 and a residence time of about 1 s, the optimum rate of etch 6H-SiC crystals grown by the natural Lely method was about 80 nm min−1. After 20 min of etching, the surface morphology was investigated by atomic force microscopy. It was found very satisfactory with no evidence of large residues. Finally, the selectivity of Al and Ni masking was investigated. With respect to bulk 6H-SiC, we have found about 16 for Al and 40 for Ni.