Effects of boron diffusion in pMOSFETs with TiN-HfSiO gate stack

Boron diffusion in TiN-HfSiO gate stack capped with polysilicon layer has been studied. SIMS analysis indicates that a significant amount of B diffused from B-doped polysilicon through TiN layer into nitrided HfSiO gate dielectrics. Grain boundaries in TiN thin film are considered a conduit of B into HfSiO. Even though most of B was stopped within HfSiO film owing to N incorporation, significant V/sub t/ shift and interface properties degradation were observed. It was found that B in HfSiO serves as positive charge and shifts pMOSFET V/sub t/ to negative side.