Models for the SiSiO 2 interface degradation at low injected electron fluences

Abstract

Positive charge and interface state creation at the SiSiO 2 interface has been studied when low-fluence electron injections (lower than 10 −3 C/cm 2) are performed at high fields (higher than 7 MV/cm) across the oxide. Temperature dependencies for the formation of both types of interface defects are examined in the range of 90–450 K. For the injections at a field lower than a threshold field of about 8·5–9 MV/cm, the interface state generation dominates, and we do not observe a significant positive charge formation. At a higher field, both positive charges and interface states are generated. It is found that positive charge formation is temperature independent, while interface state creation is thermally activated. The former result (no temperature dependence) is consistent with impact ionization in SiO 2, while the latter (temperature dependence) is explained by a trap creation due to hydrogen-related species diffusion. These results show that both mechanisms can occur together, and that they trigger two different kinds of damage at the SiSiO 2 interface.