SELECTIVE REMOVAL OF SI1-XGEX FROM (100)-SI USING HNO3 AND HF

The selective removal of epitaxial Si1-xGex from (100) Si using an aqueous based etch consisting of nitric acid and trace hydrofluoric acid has been studied with respect to alloy composition, reaction mechanism, and surface smoothness. Selectivity, defined as the rate ratio of the Si1-xGex layer removal to the (100) Si layer removal, was better than 100 for a 30% Ge alloy layer with an etch consisting of 35:20:10, HNO3:H2O:HF (0.5%). The alloy etch rate increased with increasing Ge composition of the alloy in the germanium composition range of 10-50%. The presence of misfit dislocations was found to increase the etch rate compared to a fully strained alloy.