Recovery of negative bias temperature instability induced degradation of p-MOSFETs with SiON gate dielectric

This paper investigates the recovery property of p-MOSFETs with an ultra-thin SiON gate dielectric which are degraded by negative bias temperature instability (NBTI). The experimental results indicate that the recovery of the NBTI degradation occurs through an electrical neutralization of the NBTI-induced positive charges at the SiON/Si interface and in the gate dielectric. The neutralization of interface charges was a fast process occurring just after the device returned to the recovery state. The neutralization of positive charges in the gate dielectric was a slow process associated with the electron injection into the gate dielectric. Below the gate voltage for strong accumulation, the amount of recovery increased with an increase of the gate voltage. A further increase of gate voltage did not affect the amount of recovery. These experimental results indicate that the major cause of the recovery is a neutralization of the NBTI-induced positive charges by electrons instead of a hydrogen passivation of the NBTI-induced defect sites.