2-STAGE HOT-CARRIER DEGRADATION AND ITS IMPACT ON SUBMICROMETER LDD NMOSFET LIFETIME PREDICTION

The device degradation of oxide-spacer LDD NMOSFET's due to hot carrie rs is studied in detail. The observed saturation in the degradation ti me dependence is found to be due to a combination of an increase in th e series resistance in the lightly doped drain region, and a reduction of the carrier mobility in the channel and subdiffusion regions. The increase in series resistance eventually saturates. Thus, a more accur ate and consistent value of LDD NMOSFET lifetime can be determined usi ng extrapolations which are based on the asymptotic value of the degra dation rate coefficient.