γ-ray irradiation-induced Si-SiO2 interfacial state and its energy level distribution of its density in MOS structure

The oxide trapped charge ΔDot, the Si-SiO2 interfacial state density ΔDit and the energy level distribution of the density introduced in polysilicon gate MOS samples with n(100) silicon substrate after 60Co γ-ray irradiation are studied. Experimental evidence indicates that the effect of irradiation strongly depends on the bias field. When samples are irradiated at a + 1MV/cm bias field, both the oxide trapped charge and the interfacial state density present a peak. The midgap state density is proportional to the density of holes trapped. While the interfacial state density of polysilicon gate MOS samples in the forbidden band obeys the U-type distribution, a broad peak of interfacial state density with definite energy level (Ec - Es = 0.41 - 0.5 eV) appears in the Al-gate n substrate MOS samples after irradiation