Enhancing SiOx Protection during SiGe Selective Wet Etch in CFET Integration Using Oxide Surface Functionalization

This work describes the OSF concept (Oxide Surface Functionalization) as being a pre-treatment before a wet SiGe removal within the CFET integration. The SiGe is removed with an HF_H₂O₂ formulated chemistry that induces some oxide loss in the CFET structures (hard mask and STI). The OSF consists in a selective coating that occurs on the oxide surfaces and not on the SiGe surfaces that need to be removed. The selective coating prevents the oxide surface of being significantly etched during the wet SiGe removal.