COMPARISON OF THE GENERATION OF INTERFACE STATES IN MOS STRUCTURES DUE TO CO-60 AND VUV IRRADIATION ACCOMPANIED WITH PHOTOINJECTION OF ELECTRONS

The buildup of interface states in MOS structures with differently ann ealed oxides is studied under vacuum ultraviolet (VUV) and Co-60 irrad iation. A larger creation of interface states is observed if photoinje ction of electrons is applied simultaneously with the VUV irradiation. The presence of electrons at the Si/SiO2 interface favors the generat ion and explains the larger amount of interface states after Co-60 irr adiation. After VUV irradiation the interface state density increases in n-samples to a specific saturation value which is reached earlier i f gate voltage is made more positive or samples are exposed to photoin jection. This is due to the increase of the radiation peak which is lo cated in the upper half of the silicon gap. The impact of post oxidati on annealing on the interface state generation is investigated due to VUV and Co-60 irradiation.