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

The effect of annealing temperature on the properties of aqueous solution-processed AlO_x thin films is reported in this paper. Specifically, the stability of AlO_x 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 (ΔN_ot) in AlO_x bulk and interface trap density (ΔN_it) at the oxide/semiconductor interface. It is been found that high annealing temperature (>250 °C) can result in the formation of AlO_x thin films with reduced impurities, low leakage current, and satisfactory BS as well as BRS stability. The results of ΔN_ot and ΔN_it vs stress time indicate that AlO_x bulk oxide traps dominate the shift of flat-band voltage (V_FB) under BRS. Furthermore, ΔN_ot and ΔN_it decrease slightly under positive biased radiation stress (PBRS), while the increase in ΔN_ot and ΔN_it concentrations observed under negative biased radiation stress (NBRS), exhibits a mechanism which differs from the traditional two-stage process theory.