BREAKDOWN PROPERTIES OF THIN OXIDES IN IRRADIATED MOS CAPACITORS

The influence of ionizing radiation on breakdown characteristics of MOS structures with thin gate oxides is investigated. It is found that, as the result of irradiation, a significant reduction in the number of medium-voltage defect-related breakdown events takes place. This improvement effect suggests that there is an interaction between defects responsible for early breakdowns and defects generated by radiation, which results in the hardening of oxide weak spots. The observed shortening of the time-to-breakdown for irradiated structures is explained in terms of radiation-induced positive charge and electron trap generation which, during subsequent TDDB stress, leads to enhancement of the internal oxide field. As the result of irradiation, a significant reduction of the field acceleration factor of oxide breakdown (determined for high, near critical electric fields) is also observed.