Characteristics and physical mechanisms of positive bias and temperature stress-induced drain current degradation in HfSiON nMOSFETs

Drain current degradation in HfSiON gate dielectric nMOSFETs by positive gate bias and temperature stress is investigated by using a fast transient measurement technique. The degradation exhibits two stages, featuring a different degradation rate and stress temperature dependence. The first-stage degradation is attributed to the charging of preexisting high-k dielectric traps and has a log(t) dependence on stress time, whereas the second-stage degradation is mainly caused by new high-k trap creation. The high-k trap growth rate is characterized by two techniques, namely 1) a recovery transient technique and 2) a charge-pumping technique. Finally, the effect of processing on high-k trap growth is evaluated.