THE DEVELOPMENT OF AN ANISOTROPIC SI ETCH PROCESS SELECTIVE TO GEXSI1-X UNDERLAYERS

In this paper we present the development of a technique for anisotropi cally etching silicon on GeSi. Wet chemical etching exhibits a selecti vity of nearly 40:1 but is completely isotropic and requires the use o f a hard mask. The fluorine plasma process which has been reported in the literature as having high selectivity was nonreproducible as a res ult of significant polymeric deposition the chamber surfaces. Furtherm ore the etch residue was not easily removed in an O2 plasma and led to highly resistive contacts. Reactive ion etch processes using BCl3/Cl2 and SiCl4 were found to anisotropically etch the silicon layer, had p oor selectively to GeSi. By combining a reactive ion etch at 300 W for ward power and 20 mTorr in SiCl4, with a wet chemical dip, an adequate process for selectively patterning submicron features was obtained.