MICRONIC N-CHANNEL MOSFET DEGRADATION UNDER STRONG AND SHORT-TIME HOT-CARRIER STRESS

We have carried out an experimental study of aging at room temperature on n-channel MOSFETs of effective length L = 1 mum, under strong and short-time hot-carrier stress. The evolution of maximum transconductance and threshold voltage is systematically studied after each stress cycle by analysing the bias conditions and channel length influence. We have analysed the degradation by comparison of static characteristics before and after the stress. We present the method used to extract the stressed MOSFET parameters and propose an empirical model of the normalized maximum transconductance degradation (DELTAG(max)/G(mo)) caused by a short-time stress at strong gate voltage. We show also that in some particular cases and in contradiction with the results published up until now in the literature, the n-channel MOSFET threshold voltage can decrease (instead of increase) after stress.