Aqueous solution-processed AlOx dielectrics and their biased radiation response investigated by an on-site technique

Abstract

The effect of annealing temperature on the properties of aqueous solution-processed AlOx thin films is reported in this paper. Specifically, the stability of AlOx based Metal Oxide Semiconductor (MOS) capacitor devices under bias-stress (BS) and biased radiation stress (BRS) were assessed by an on-site technique with bias stress time up to 105 s. A 662-keV Cs137 γ-ray radiation source was used, with circa 92 Gy, for biased radiation stress experiments. In order to better understand the origin of degradation mechanisms, the build-up of charge and generation of defects during the BS and BRS were analyzed by calculation of the variation of oxide trap density (ΔNot) in AlOx bulk and interface trap density (ΔNit) at the oxide/semiconductor interface. It is been found that high annealing temperature (>250 °C) can result in the formation of AlOx thin films with reduced impurities, low leakage current, and satisfactory BS as well as BRS stability. The results of ΔNot and ΔNit vs stress time indicate that AlOx bulk oxide traps dominate the shift of flat-band voltage (VFB) under BRS. Furthermore, ΔNot and ΔNit decrease slightly under positive biased radiation stress (PBRS), while the increase in ΔNot and ΔNit concentrations observed under negative biased radiation stress (NBRS), exhibits a mechanism which differs from the traditional two-stage process theory.