Chlorine- and Fluorine-based dry etching of Germanium-Tin

Cl- and F- based dry etching of Ge_1-xSn_x were presented in this work. High selectivity of Ge_1-xSn_x over Ge can be achieved by F-based dry etching. This is caused by the formation of a thin nonvolatile SnF_x layer at Ge_1-xSn_x surface. Addition of O₂ to CF₄ can enhance the selectivity of F-based dry etching, but with an increase of surface roughness of Ge_1-xSn_x samples.