Comparison of the generation of interface states in MOS structures due to 60Co and VUV irradiation accompanied with photoinjection of electrons

The buildup of interface states in MOS structures with differently annealed oxides is studied under vacuum ultraviolet (VUV) and ⁶⁰ Co irradiation. A larger creation of interface states is observed if photoinjection of electrons is applied simultaneously with the VUV irradiation. The presence of electrons at the Si/SiO₂ interface favors the generation and explains the larger amount of interface states after ⁶⁰Co irradiation. After VUV irradiation the interface state density increases in n-samples to a specific saturation value which is reached earlier if the gate voltage is made more positive or samples are exposed to photoinjection. This is due to the increase of the radiation peak which is located in the upper half of the silicon gap. The impact of post oxidation annealing on interface state generation is investigated due to VUV and ⁶⁰Co irradiation