Evidence for defect pairs in SiON pMOSFETs

Detailed time-dependent defect spectroscopy (TDDS) studies have recently demonstrated that recovery following negative bias temperature stress in MOSFETs is to good approximation consistent with a collection of independent (effective) first-order reactions. While the data are largely consistent with the first-order picture, several `anomalies' such as switching traps and disappearing/reappearing traps have already been identified and analyzed. Here, we focus on a newly made observation, namely that emission events apparently belonging to a single defect can in fact be composed of two subsequent emission events if the device is stressed for a long enough time. We analyze this peculiarity as a function of bias and temperature and conclude that it is most likely due to a pair of defects which for some reason have similar configurations and thus similar properties.