Radiation induced leakage current and stress induced leakage current in ultra-thin gate oxides

Low-field leakage current has been measured in thin oxides after exposure t o ionising radiation. This Radiation Induced Leakage Current (RILC) can be described as an inelastic tunnelling process mediated by neutral traps in t he oxide, with an energy loss of about 1 eV. The neutral trap distribution is influenced by the oxide field applied during irradiation, thus indicatin g that the precursors of the neutral defects are charged, likely being defe cts associated to trapped holes. The maximum leakage current is found under zero-field condition during irradiation, and it rapidly decreases as the f ield is enhanced, due to a displacement of the defect distribution across t he oxide towards the cathodic interface. The RILC kinetics are linear with the cumulative dose, in contrast with the power law found on electrically s tressed devices.