RAPID PLASMA-ETCHING OF CUBIC SIC USING NF3 O-2 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 r ates are needed. We made a systematic study of plasma etching processe s with NF3/O-2 gas mixtures. Silicon substrates with epitaxial beta-Si C layers on top and poly-crystalline, but well orientated beta-SiC bul k substrates were used for the etching experiments. As mask materials both evaporated and sputtered aluminium layers, partly with chromium a dhesive layers, were applied. We investigated the dependence of the et ch rate on the O-2 content in the gas mixture, the substrate temperatu re and the gas pressure. We reached etch rates up to 1 mu m min(-1) at the best etching conditions. The etching selectivity of beta-SiC comp ared 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 beta-SiC were observed. (C) 1997 Else vier Science S.A.