HARDNESS-ASSURANCE ISSUES FOR LATERAL PNP BIPOLAR JUNCTION TRANSISTORS

The dose-rate dependence of gain degradation in lateral PNP transistor s is even stronger than the dependence previously reported for NPN BJT s. In this work, several hardness-assurance approaches are examined an d compared to experimental results. obtained at low dose rates. The ap proaches considered include irradiation at high dose rates while at el evated temperature and high-dose-rate irradiation followed by annealin g. The lateral PNP transistors continue to degrade during post-irradia tion annealing, in sharp contrast to NPN devices studied previously. H igh-temperature conditions significantly increase the degradation duri ng high-dose-rate irradiation, with the amount of degradation continui ng to increase with temperature throughout the range studied here (up to 125 degrees C). The high-temperature degradation is nearly as great as that observed at very low dose rates, and is even greater when dif ferences between Co-60 and x-ray irradiation are accounted for. Since high-temperature irradiation has previously been shown to enhance the degradation in NPN transistors, this appears to be a promising hardnes s-assurance approach for bipolar integrated circuits. Based on these r esults, preliminary testing recommendations are discussed.