Insight Into the Suppressed Recovery of NBTI-Stressed Ultrathin Oxynitride Gate pMOSFET

It has been observed that the ultrathin oxynitride gate pMOSFET is resistant to post-negative-bias-temperature-instability (post-NBTI) recovery. The resistance to recovery is due mainly to the locking in of stress-induced positive interfacial/bulk oxide defects at deep energy levels (above the conduction band edge of the Si n-well) outside the energy window of electron direct tunneling. As a consequence, these defect states can remain positively charged for a long period in the ultrathin gate dielectric, even under positive gate biasing. Results show that nitrogen increases the density of deep-level oxide defect precursors, thus raising the resistance of the ultrathin gate pMOSFET to post-NBTI recovery