Effect of Body Bias on NBTI of p-MOSFETs

The effect of the body bias on the stability of the threshold voltage of p
⁺
polysilicon gate p-channel MOS (pMOS) transistors stressed in the on-state is investigated. Special attention is given to pMOS transistors operating at low gate overdrive and non-zero body voltage. A mixed mode of degradation, including the usual negative bias temperature instability (NBTI) and the effect of hot-hole injection (HHI) into the gate oxide at high temperature, is reported. The relative importance of both the electric field in the gate oxide and the concentration of cold holes at the interface is pointed out for devices operating in the near threshold region. A kinetic model for NBTI/HHI is proposed.