Atomistic model of electric stress induced defect generation in silicon oxide

The initial steps of gate oxide wear-out phenomenon are considered using quantum mechanical cluster density functional theory calculations. As was proposed earlier, precursor breakdown defects can be formed due to capture of the injected electrons by localized gap states induced by structural imperfections in SiO2. In this publication, we have shown that the electron capture weakens the Si–O bond, which can then be broken due to its polarization and vibrational excitation. In the next step, a donor–acceptor bond between the negatively charged oxygen and neighboring silicon atom may be formed creating a chain of bond swapping. The proposed model suggests a novel mechanism for the formation of paramagnetic defects in the oxides (E′ centers), which can contribute to the formation of a conduction path in the oxide film and its dielectric breakdown. The proposed model describes the observed charge-to-breakdown dependence on electric field, temperature, electron fluence, and oxide thickness.