Observation of two gate stress voltage dependence of NBTI induced threshold voltage shift of ultra-thin oxynitride gate p-MOSFET

Ultra-fast measurement of NBTI induced threshold voltage shift (|DeltaV_t|) reveals two |DeltaV_t| components that exhibit different dependence on the stress time and the gate stress voltage V_g ^s. One component is spontaneously generated upon stress, i.e. fast generation, and the amount generated saturates within the first few seconds of stress. The saturation level is observed to scale linearly with V_g ^s. The second component increases steadily with stress time, i.e. it exhibits a relatively slow generation rate; its stress time dependence may be described by a power-law with exponent n asymptotically approaching ~0.167 at steady state. This component exhibits an exponential/power-law dependence on V_g ^s.