Dry etching method

Abstract

A dry etching method for performing anisotropic etching of a layer of a silicon based material without using a chlorofluorocarbon gas, is proposed. Sulfur halides yielding free sulfur (S) into a plasma under conditions of dissociation by electrical discharge, such as S.sub.2 F.sub.2 or S.sub.2 Cl.sub.2, are used as main components of the etching gas. This S is used for sidewall protection and for improving selectivity during etching, and is removed by sublimation by heating the wafer after etching. Although etching may be achieved by S.sub.2 F.sub.2 alone, suitable measures may preferably be used to increase the S/X ratio of an etching reaction system, which is a ratio of the number of atoms of S to that of X or a halogen, because the layer of the silicon based material is highly susceptible to halogen radicals. Specifically, optimum results may be obtained by (a) adding H.sub.2, H.sub.2 S or SiH.sub.4 to the etching gas, (b) introducing hydrogen in advance into an area for etching by ion implantation, (c) using a silicon-containing resist mask, or (d) by coating the surface of a wafer cover with an amorphous silicon layer.