The degradation of p-MOSFETs under off-state stress
The hot carrier effects under off-state stress mode (Vgs=0V; Vds<0V) have been investigated on 9nm p-MOSFETs with channel length varying from 1.025 to 0.525?m. Both on- and off-state currents are discussed in this paper. It is found that the off-state leakage current will decrease after higher stressing voltage, which is induced by charge injection occurring close to the drain junction. However, the leakage current will increase after lower stressing voltage because of the newly generated interface traps. It is also found that the on-state saturation current and threshold voltage degraded significantly with stress time, which we believe is due to the charges injected near the gatedrain overlapping region and/or the stress-induced interface trap generation. The degradation of Idsat can be expressed as a function of the product of the gate current (Ig) times the number of charges injected into the gate oxide (Qinj) in a simple power law. Finally, a lifetime prediction model based on the degradation of Idsat is proposed.
degradation p-mosfets off-state stress gidl