Bias-temperature instabilities of polysilicon gate HfO2 MOSFETs

Bias-temperature instabilities (BTI) of HfO2 metal oxide semiconductor field effect transistors (MOSFETs) have been systematically studied for the first time. NMOS positive BTI (PBTI) exhibited a more significant V-t instability than that of PMOS negative BTI (NBTI), and limited the lifetime of HfO2 MOSFETs. Although high-temperature forming gas annealing (HT-FGA) improved the interface quality by passivating the interfacial states with hydrogen, BTI behaviors were not strongly affected by the technique. Charge pumping measurements were extensively used to investigate the nature of the BTI degradation, and it was found that V-t degradation of NMOS PBTI was primarily caused by charge trapping in bulk HfO2 rather than interfacial degradation. Deuterium (D-2) annealing was found to be an excellent technique to improve BTI immunity as well as to enhance the mobility of HfO2 MOSFETs.