Silicon germanium processing

Abstract

Methods of selectively etching silicon germanium relative to silicon are described. The methods include a remote plasma etch using plasma effluents formed from a fluorine-containing precursor. Plasma effluents from the remote plasma are flowed into a substrate processing region where the plasma effluents react with the silicon germanium. The plasmas effluents react with exposed surfaces and selectively remove silicon germanium while very slowly removing other exposed materials. Generally speaking, the methods are useful for removing SiGe(including germanium i.e. X=1) faster than SiGe, for all X>Y. In some embodiments, the silicon germanium etch selectivity results partly from the presence of an ion suppression element positioned between the remote plasma and the substrate processing region.