Intrinsic Effect of a Nitrogen Atom on Hf-based High-k Gate Dielectrics -A First Principles Study

We theoretically investigate the nitrogen incorporation effect in hafnia (HfO$_{2})$ from the first- principles calculations within GGA framework, especially focusing on the interaction between N atoms and O vacancies (Vo)s. Vo is known to be problematic for Hf-based high-k gate dielectrics because it causes unfavorable charge trap. Moreover, some experimental results suggest that Vo related gap states$_{ }$assist the electron leakage current, which deteriorates the electrical properties of Hf-based MOSFETs. Our results clearly show that N atoms selectively occupy nearby O sites of Vo and that Vo levels are completely eliminated by the N incorporation. These results clearly show that N atoms have intrinsic effects to decrease Vo related gap states, leading to the reduction in both the number of charge trap sites and the leakage current through HfO$_{2}$.