Characterization and numerical analysis of breakdown in thick amorphous SiO2 capacitors

Charge transport in thick amorphous silicon dioxide capacitors for integrated galvanic insulators is experimentally investigated and analyzed through numerical simulations carried out with a commercial TCAD tool. The material intrinsic defectivity and the large biases applied to such devices give rise to a leakage current which is responsible for degradation and failure. Hence it is crucial to have a complete understanding of the charge-transport main physical mechanisms in amorphous silicon oxide. In particular, charge injection at contacts and charge build-up due to trapping/de-trapping mechanisms in the bulk of the oxide are expected to play a crucial role and their complex coupled interaction needs to be investigated via a TCAD-based approach. For this reason, time-dependent dielectric breakdown measurements at constant-current stresses and voltage-ramp stresses up to breakdown have been performed on thick metal-insulator–metal structures, and numerical simulations have been carried out so to predict the failure mechanisms. To this purpose, special attention has been devoted to the physical modeling of defects and impact-ionization generation.