Extended Time Dependent Dielectric Breakdown Model Based on Anomalous Gate Area Dependence of Lifetime in Ultra Thin Silicon Dioxides

The conventional time dependent dielectric breakdown (TDDB) model is extended for ultra thin silicon dioxides on the basis of the four stage dielectric breakdown process model (FSM), in which the dielectric breakdown process consists of two individual processes: the “partial breakdown” and the “complete breakdown”. The lifetime measured under constant voltage stressing shows an anomalous gate area dependence as predicted by the extended TDDB model. This model can be adopted not only for the ultra thin oxides but also for oxides where the partial breakdown takes place. The conventional TDDB model is regarded as a case in which the time to complete breakdown after the partial breakdown is ignored compared to the time to partial breakdown. Furthermore, it is demonstrated that one cannot obtain an accurate lifetime without taking into account the extended TDDB model.