A STUDY OF HOT-CARRIER DEGRADATION IN NMOSFETS BY GATE CAPACITANCE AND CHARGE-PUMPING CURRENT

Hot carrier degradation in n-channel MOSFET's is studied using gate ca pacitance and charge pumping current for three gate stress voltages: V -g similar to V-t, V-d/2, V-d. The application of these two sensitive techniques reveals new information on the types of trap charges and th e modes of degradation. At low V-g stress near threshold voltage, the fixed charge is attributed to holes. For high V-g stress, the fixed ch arge is predominantly electrons. Data for mid V-g stress suggest littl e net fixed charge trapping. Interface traps are observed for all stre ss conditions and are demonstrated from differential gate capacitance spectra to exhibit both donor and acceptor trap behavior, Mid V-g stre ss is shown to result in the highest density of interface traps. These traps can be annealed to a large extent for temperatures up to 300 de grees C. A post-stress generation of interface trap is observed at low V-g stress, in agreement with recent observation. Further, a linear r elation is found to exist between the change in overlap gate capacitan ce and the increase in peak charge pumping current, and suggests spati al uniformity in the degradation of the interface.