Electron radiation effects on time-dependent dielectric breakdown in SiO2 films

An experiment testing the effect of ionizing radiation on breakdown characteristics of SiO2 films is presented. Silicon wafers were oxidized and metallized, and a capacitor array was etched into a control sample while the rest were first irradiated with 1 MeV electrons and then etched. Time-dependent dielectric tests were made on all the capacitors, and the average characteristics of 96 capacitors are illustrated graphically. The curves are consistent with the model of holes trapped in the SiO2 film during irradiation leading to a retarding field for positive ion emission and drift toward the interface. It is shown how an externally applied field is reduced by the trapped charge, and that changes in the dielectric breakdown properties of the SiO2 film after irradiation depend on the positive trapped charge near the metal interface.