Valence-band tunneling enhanced hot carrier degradation inultrathin oxide nMOSFETs

摘要

Enhanced hot carrier degradation with stress V_g in thevalence-band tunneling regime is observed. This degradation isattributed to channel hole creation by valence-band electron tunneling.The created holes provide for Auger recombination with electrons in thechannel and thus increase hot electron energy. The valence-bandtunneling enhanced hot carrier degradation becomes more serious as gateoxide thickness is reduced. In ultrathin gate oxide nMOSFETs, our resultshows that the valence-band tunneling enhanced degradation, as opposedto max. I_b stress induced degradation, exhibits positivedependence on substrate bias. This phenomenon may cause a severereliability issue in positively biased substrate or floating substratedevices