Universal recovery behavior of negative bias temperature instability [PMOSFETs]

Abstract

PMOSFETs experiencing negative bias temperature instability (NBTI) recover after stress is removed. We show for the first time that: (1) the recovery can reach 100% at 25/spl deg/C; (2) recovery has a universal behavior independent of stress voltage, stress time and temperature (below 25/spl deg/C); and (3) the recovered devices degrade at the same rate when re-stressed, indicating that recovery resets the degraded device to its original state. We propose a three step model to describe this mechanism: (i) voltage accelerated degradation, (ii) bias and degradation independent recovery and (iii) temperature driven "lock-in" step. We believe that the competing effects of these three steps corrupt common field/temperature acceleration models for NBTI.