First-principles studies of the intrinsic effect of nitrogen atoms on reduction in gate leakage current through Hf-based high- k dielectrics

The atomistic effects of N atoms on the leakage current through Hf O2 high- k gate dielectrics have been studied from first-principles calculations within the framework of a generalized gradient approximation (GGA). It has been found that the intrinsic effects of N atoms drastically reduce the electron leakage current. N atoms couple favorably with oxygen vacancies (VO) in Hf O2 and extract electrons from VO. As a result, VO energy levels are drastically elevated due to the charged-state change in VO from neutral (VO0) to positively charged (VO 2+). Accordingly, N incorporation removes the electron leakage path mediated by VO related gap states.