Microstructural Variations in Radiation Hard and Soft Oxides Observed through Electron Spin Resonance

We find that the radiation tolerance of MOS oxides is correlated with two "trivalent silicon" centers, one in the oxide (E'), one at the Si/SiO2 interface (Pb). We earlier demonstrated a strong correlation between radiation induced Pb concentration and raradiation induced interface state density in relatively soft dry oxide structures. In this paper we report a similar correlation between the density of E' centers (likely holes trapped in oxygen vacancies) and the density of holes trapped in the oxide. We thus have obtained evidence for a microstructural model of both interface states and hole traps. Processing improvement efforts may now be guided by some fundamental understanding of the device degradation process.