Interface trap passivation effect in NBTI measurement for p-MOSFET with SiON gate dielectric

New findings of interface trap passivation effect in negative bias temperature instability (NBTI) measurement for p-MOSFETs with SiON gate dielectric are reported. We show evidence to clarify the recent debate: the recovery of V_th shift in the passivation phase of the dynamic NBTI is mainly due to passivation of interface traps (N_it), not due to hole de-trapping in dielectric hole traps (N_ot). The conventional interface trap measurement methods, dc capacitance-voltage and charge pumping, seriously underestimate the trap density N_it. This underestimation is gate bias dependent during measurement, because of the accelerated interface trap passivation under positive gate bias. Due to this new finding, many of previous reliability studies of p-MOSFETs should be re-investigated.