Quasi-breakdown in ultra-thin oxides: some insights on the physical mechanisms
This paper discusses the variation of the probability to observe quasi-breakdown with capacitor topology and stress conditions and gets some insights on the physical mechanisms of both breakdown and quasi-breakdown phenomena. To achieve this goal, a methodology based on competing mechanisms between breakdown and quasi-breakdown is introduced in order to rigorously analyze Time Dependent Dielectric Quasi-breakdown. This approach is found to provide specific and distinct parameters for breakdown and quasi-breakdown, such as Weibull slope, acceleration factor and activation energy, which enable to well model the quasi-breakdown rate behavior with the capacitor topology and the stress conditions. This good adequation first validate this methodology and undoubtedly indicates that the physical defects at the origin of both phenomena are different. Additionally, the quasi-breakdown is demonstrated to occur on a reduced window of carrier energy, what confirms the distinct origins of both phenomena. Moreover, this induces some important consequences concerning reliability extrapolation, since the critical failure mode can be different at high field than at nominal condition.