US Patent 9576809 Etch suppression with germanium

Methods of selectively etching silicon relative to silicon germanium are described. The methods include a remote plasma etch using plasma effluents formed from a fluorine-containing precursor and a hydrogen-containing precursor. Plasma effluents from the remote plasma are flowed into a substrate processing region where the plasma effluents react with the silicon. The plasmas effluents react with exposed surfaces and selectively remove silicon while very slowly removing other exposed materials. The methods are useful for removing Si(1-X)GeX faster than Si(1-Y)GeY, for 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.