Function-fit model for the rate of conducting filament generation in constant voltage-stressed multilayer oxide stacks

Abstract

A simple function-fit model is proposed for the rate of conducting filament generation in Al2O3/HfO2-based multilayer stacks subjected to a constant voltage stress. During degradation, the devices exhibit stepwise current–time (I-t) characteristics that can be straightforwardly linked to the triggering of multiple breakdown events. The stochastic nature of this stepwise behavior is phenomenologically modeled by means of a nonhomogeneous Poisson process for the arrival rate of the individual failure events. In this work, it is shown that a power-law model for the failure rate in combination with an equivalent circuit representation of the device under stress accounts for the evolution of the I-t curve, providing a first-order estimation of the stress time required to reach a targeted leakage current level. The roles played by the device area and stress voltage on the breakdown dynamics are also investigated.