Observation of latent reliability degradation in ultrathin oxides after heavy-ion irradiation

Constant voltage time-dependent-dielectric-breakdown distributions were obtained for both unirradiated and irradiated 3.0 and 3.2 nm thick SiO2 films subjected to 60Co gamma irradiation and heavy ions of 823 MeV 129Xe (linear energy transfer=59 MeV-cm2/mg). The gamma irradiation had no effect on oxide lifetime. The heavy ion irradiation substantially reduced oxide life even though the devices were biased at 0.0 V during irradiation. The reduction of oxide lifetime under constant-voltage stress conditions was a strong function of the heavy ion fluence.