Annealing behavior of linear bipolar devices with enhanced low-dose-rate sensitivity

The post-irradiation annealing behavior of total dose degradation in LM139 comparators fabricated in National Semiconductor Corporation´s (NSC) enhanced low-dose-rate sensitive (ELDRS) linear bipolar technology is examined. Data show that a large fraction of the radiation-induced increase in input bias current recovers after a 100°C anneal. The recovery in input bias current is linked to a significant amount of interface-trap annealing at 100°C. This is qualitatively consistent with previous data on interface-trap annealing and recent models for interface-trap annealing associated with hydrogen motion at the silicon/silcon dioxide interface. The annealing results have implications for hardness assurance testing. If the radiation induced charge that is responsible for ELDRS (whether it be interface or border traps) can anneal at 100°C, these data suggest that elevated temperature irradiations sometimes used to bound the ELDRS response of ICs may also cause some annealing of radiation-induced charge. These data help explain why high-dose-rate irradiations at elevated temperatures in some cases underestimate low-dose-rate degradation. In addition, these data confirm that high-dose-rate irradiations followed by elevated temperature anneals do not mimic the mechanisms that cause enhanced degradation at low dose rates in devices with ELDRS.