Probabilistic defect occupancy model for NBTI

A new Negative Bias Temperature Instability (NBTI) model based on the probability of charge/discharge of defects in devices is presented. The model correctly describes the main experimental NBTI features, such as the threshold voltage shift (ΔV_T) evolution under DC or AC stresses, its frequency and duty cycle dependence and the statistical ΔV_T distribution in small transistors. Finally, the model is used to explain the dependence of NBTI degradation on the stress/relaxation times, frequency and duty cycle in terms of defect occupancy.