Modeling trap generation process in thin oxides

A bond-breaking phenomenon responsible for oxide degradation during electrical stress is considered as a multi-step process that includes creation of a breakdown precursor defect and the subsequent breakdown of the defect's bond. Precursor defect generation is described as the scattering of the injected electrons by the localized states associated with the strained oxide bonds, presumed to be Si-O-Si bonds. Collision-induced electronic excitation of the strained bond can result in the formation of a structural defect, in particular Si-Si, which is shown to be unstable due to its polarization and vibrational excitation induced by an applied electric field and temperature, respectively. The proposed model suggests that these precursor defects are preferentially generated in the vicinity of the already existing O-vacancies in the oxide. This leads to the formation of a defect cluster which can propagate through the oxide. The model describes the charge-to-breakdown dependence on the electron fluence and energy, stress bias, electric field, temperature and oxide thickness.