Gate Rupture in Ultra-Thin Gate Oxides Irradiated With Heavy Ions

We investigated the combined effect of heavy-ion irradiation and large applied bias on the dielectric breakdown of ultrathin gate oxides, analyzing the impact of border regions through dedicated test structures. We found that the irradiation bias polarity plays a fundamental role, with inversion being more detrimental than accumulation for the onset of gate rupture. Moreover, the average voltage to breakdown was, under certain conditions, lower in structures more closely resembling real MOSFETs, as compared to those commonly used for the evaluation of Single Event Gate Rupture. These findings raise some important hardness assurance issues concerning the integrity of gate oxides in radiation environments.