NBTI Degradation and Recovery in Analog Circuits: Accurate and Efficient Circuit-Level Modeling

We investigate the negative-bias temperature instability (NBTI) degradation and recovery of pMOSFETs under continuously varying analog-circuit stress voltages and thereby generalize existing digital-stress NBTI studies. Starting from our ultrafast NBTI measurements and an extensive TCAD analysis, we study two physics-based compact models for analog-stress NBTI including recovery. The high accuracy of both models is evidenced from single-FET analog-stress and circuit-level ring oscillator experiments. Their numerical efficiency allows direct coupling to circuit simulators and permits to accurately account for NBTI already during circuit design. Furthermore, one of the models calculates the time-dependent NBTI variability of single-FET and of circuit performance parameters. We demonstrate our NBTI models on a ring oscillator and calculate the mean drift and statistical distribution of its oscillation frequency.