Role of hydrogen in Ge/HfO₂/Al gate stacks subjected to negative bias temperature instability

This work investigates the role of hydrogen and nitrogen in a GeHf O2 Al gate stack by comparing the negative bias temperature instability (NBTI) characteristics with and without the surface nitridation of Ge surface prior to Hf O2 deposition. Flatband voltage shift, change in interface state density, and stress induced leakage current were also monitored as a function of stress time. Virtually unchanged interface state density as a function of NBTI indicates no atomic hydrogen release from the dangling bond sites. However, the low n value in power law dependence of flatband voltage shift suggests diffusion of molecular hydrogen absorbed at the interface.