Rapid plasma etching of cubic SiC using NF3/O2 gas mixtures

SiC is known as a chemically inert material. Therefore structuring of SiC by dry chemical processes is difficult and the reported etch rates are usually low. For sensor and micro-machining applications, however, three-dimensional structuring processes of bulk SiC with high etch rates are needed. We made a systematic study of plasma etching processes with NF3/O2 gas mixtures. Silicon substrates with epitaxial β-SiC layers on top and poly-crystalline, but well orientated β-SiC bulk substrates were used for the etching experiments. As mask materials both evaporated and sputtered aluminium layers, partly with chromium adhesive layers, were applied. We investigated the dependence of the etch rate on the O2 content in the gas mixture, the substrate temperature and the gas pressure. We reached etch rates up to 1 μm min −1 at the best etching conditions. The etching selectivity of β-SiC compared to other semiconductor materials was studied. An etch rate ratio of SiC to Si and SiO2 of 4–5 was achieved. Furthermore differences in the etch rates of p- and n-doped β-SiC were observed.