Mechanism of Selective Etching of SiGe Layers in SiGe/Si Systems

Selective lateral etching of the SiGe layer for various Si/SiGe/Si systems was studied. We showed the different etching rates for SiGe layers with the same thickness and Ge concentration, but with different structures of the Si/SiGe/Si stacked layer. We described a mechanism that could explain the experimental results of selective etching of SiGe layers in Si/SiGe/Si systems. According to the mechanism, we were able to summarize the following 3 key points in realizing high selectivity SiGe etching. 1) Should be the SiGe layer in a higher oxidation state (enough number of holes), 2) a wider area is necessary for Si substrate surface in contact with the solution, and 3) the current path should be maintained at the SiGe/Si interface.