Channel hot carrier stress on irradiated 130-nm NMOSFETs: Impact of bias conditions during X-ray exposure

We investigate how X-ray exposure impact the long term reliability of 130-nm NMOSFETs as a function of device geometry and irradiation bias conditions. This work focuses on electrical stresses on n-channel MOSFETs previously irradiated with X-ray up to 136 Mrad(SiO₂) in different bias conditions. Irradiation is shown to negatively affect the degradation during subsequent hot carrier injection. Increasing the bias during irradiation slightly reduces the impact on electrical stress in core MOSFETs. We attribute these effects to an enhanced impact ionization at the bulk-STI interfaces due to radiation-induced trapped charge and defects.