The Role of Irradiation Bias on the Time-Dependent Dielectric Breakdown of 130-nm MOSFETs Exposed to X-rays

We have investigated the effects of biased and unbiased X-ray irradiation on the subsequent time-dependent dielectric breakdown (TDDB) of 130-nm MOSFETs irradiated up to $1~{\rm Mrad}({\rm SiO}_{2})$. We found a small but measurable increase in TDDB lifetime after irradiation at the worst-case irradiation bias. The influence of radiation bias on subsequent TDDB is more significant in the PMOSFETs than the NMOSFETs. The increased TDDB lifetime and the irradiation-bias dependence are attributed to the influence of radiation-induced traps on the stressing current during the reliability testing.