New understanding on the single-trap response under NBTI stress and the resulted stochastic degradation in nanoscale MOSFETs

In nano-MOSFETs, single trap induced V_th degradation becomes more serious with the scaling of the gate area, which has attracted increasing attention. The single-trap response under NBTI stress can severely impact the predictions of degradation. Based on the statistical trap-response (STR) characterizing method, the time-dependent statistics of the single-trap occupancy probability distribution under NBTI stress in highly-scaled MOSFETs is interestingly found to be Weibull distribution, rather than the conventional theory expected exponential distribution like in RTN. The detailed basic physics is found to be originated from the additional intermediate states activated under high stress and the resulting stochastic transition rates in the capture process. The single-trap random occupancy behaviors highlight the significance of trap-aware and reliability-aware circuits design.