Low-Field Current on Thin Oxides After Constant Current or Irradiation Stresses

Low-field leakage current appears as one of the main issues of very thin oxides, which may lead to the failure of single MOS and complex circuits, long before the oxide catastrophic breakdown. A large amount of work is currently dedicated to investigate how electrical stresses can enhance such a current, but few is known on the effects of ionizing radiation. In a previous work [1], we have shown that a stable leakage current at fields lower than those required for Fowler-Nordheim (FN) tunneling can be measured, even after exposure to  radiation. This Radiation Induced Leakage Current (RILC) is similar to the usual Stress Induced Leakage Current (SILC) observed after electrical stresses on MOS devices. In the present work we study RILC after exposure to a 8 MeV electron beam, on devices with different oxide thickness. We investigate the kinetics of the RILC growth with the cumulative dose, and we compare it with the kinetics of the SILC growth with the cumulative injected charge. We also address the RILC dependence from the gate bias applied during the radiation stress, in order to analyze the oxide damage distribution that induces RILC.