Study on the drain bias effect on negative bias temperature instability degradation of an ultra-short p-channel metal-oxide-semiconductor field-effect transistor

This paper studies the effect of drain bias onultra-short p-channel metal-oxide-semiconductor field-effecttransistor (PMOSFET) degradation during negative bias temperature(NBT) stress. When a relatively large gate voltage is applied, thedegradation magnitude is much more than the drain voltage which isthe same as the gate voltage supplied, and the time exponent getslarger than that of the NBT instability (NBTI). With decreasingdrain voltage, the degradation magnitude and the time exponent allget smaller. At some values of the drain voltage, the degradationmagnitude is even smaller than that of NBTI, and when the drainvoltage gets small enough, the exhibition of degradation becomesvery similar to the NBTI degradation. When a relatively large drainvoltage is applied, with decreasing gate voltage, thedegradation magnitude gets smaller. However, the time exponentbecomes larger. With the help of electric field simulation, thispaper concludes that the degradation magnitude is determined by thevertical electric field of the oxide, the amount of hot holesgenerated by the strong channel lateral electric field at thegate/drain overlap region, and the time exponent is mainlycontrolled by localized damage caused by the lateral electricfield of the oxide in the gate/drain overlap region where hot carriersare produced.