HARDNESS-ASSURANCE AND TESTING ISSUES FOR BIPOLAR BICMOS DEVICES/

Different hardness-assurance tests are often required for advanced bip olar devices than for CMOS devices. In this work, the dose-rate depend ence of bipolar current-gain degradation is mapped over a wide range o f dose rates for the first time, and it is very different from analogo us MOSFET curves. Annealing experiments following irradiation show neg ligible change in base current at room temperature, but significant re covery at temperatures of 100 degrees C and above. In contrast to what is observed in MOSFET's, irradiation and annealing tests cannot be us ed to predict the low-dose-rate response of bipolar devices. A compari son of x-ray-induced and Co-60 gamma-ray-induced gain degradation is r eported for the first time for bipolar transistors. The role of the em itter bias during irradiation is also examined. Implications fdr harde ning and hardness assurance are discussed.