Statistical model for stress-induced leakage current and pre-breakdown current jumps in ultra-thin oxide layers

We present a statistical, unified picture of Stress-Induced Leakage Current (SILC) generation, pre-breakdown current steps and breakdown in 2.4 nm oxide layers during a constant voltage stress. Pre-breakdown current steps were investigated through gate voltage ramp measurements and modeled by means of a percolation model with variable trap-trap distance. During oxide stress, first single-trap conduction paths are formed, followed by two-trap conduction paths which are identified as pre-breakdown current steps in small devices. Finally, a highly conducting path is formed which triggers breakdown.