MODIFICATIONS OF FOWLER-NORDHEIM INJECTION CHARACTERISTICS IN GAMMA-IRRADIATED MOS DEVICES

In this work we have investigated how gamma irradiation affects the tu nneling conduction mechanism of a 20 nm thick oxide in MOS capacitors. The radiation induced positive charge is rapidly compensated by the i njected electrons, and does not impact the gate current under positive injection after the first current-voltage measurement. Only a transie nt stress induced leakage current at low gate bias is observed. Instea d, a radiation induced negative charge has been observed near the poly silicon gate, which enhances the gate voltage needed for Fowler-Nordhe im conduction at negative gate bias. No time decay of this charge has been observed. Such charges slightly modify the trapping kinetics of n egative charge during subsequent electrical stresses performed at cons tant current condition.