Correlated Defect Creation in HfO2 films

Spatially correlated defect generation process has been proposed to be responsible for TDDB Weibull slope measured in HfO2. We investigated possible mechanisms for correlated defect production in amorphous (a) HfO2 films under applied stress bias using ab initio simulations. During bias application, electron injection into these films leads to the localization of up to two electrons at intrinsic trapping sites present due to the structural disorder in amorphous structures and to formation of O vacancies. Trapping of two extra electrons at a pre-exiting O vacancy facilitate the formation of a new vacancies affecting TDDB statistics and its dependence on the film thickness.