CHEMICAL ETCHING OF SI1-XGEX IN HF-H2O2-CH3COOH

The properties of a highly selective chemical etchant composed of hydr ofluoric acid, hydrogen peroxide, and acetic acid (HF;H2O;CH3COOH) is investigated in etching SiGe/Si heterostructures. This solution has be en found to etch Si1-xGex much faster than Si over the entire range of Ge contents. The etch rate dependences are presented as functions of solution composition, Ge content, dopant type, diluent type, temperatu re, and stirring. Both n-type and p-type Si1-xGex layers with Ge conte nts of 0 less than or equal to x less than or equal to 0.60 and 0 less than or equal to x less than or equal to 1.00, respectively, are inve stigated. It is found that the n-type faster rate than p-type for all Ge contents examined. When CH3COOH is used as the diluent instead of H 2O a significant enhancement in the etch rate results for all concentr ations of Ge studied. Also, the amount of H2O2 in the presence of CH3C OOH has a significant effect on the magnitude of the etch rate as well as its behavior over time.