US Patent 7682985 Dual doped polysilicon and silicon germanium etch

A method for etching a stack with at least one silicon germanium layer over a substrate in a processing chamber is provided. A silicon germanium etch is provided. An etchant gas is provided into the processing chamber, wherein the etchant gas comprises HBr, an inert diluent, and at least one of O2 and N2. The substrate is cooled to a temperature below 40° C. The etching gas is transformed to a plasma to etch the silicon germanium layer.