Selective dry etching of silicon with respect to germanium

We describe a plasma-based dry etching procedure which permits selective etching of Si over Ge with a Si/Ge etch rate ratio of over 70 and negligible etching of the Ge underlayer. This is achieved in a SF6/H 2/CF4 gas mixture by the formation of a thin (≅3 nm) involatile etch stop layer on the Ge surface which consists of Ge-sulfide and carbonaceous material.