Hardness-assurance and testing issues for bipolar/BiCMOS devices

The dose-rate dependence of bipolar current-gain degradation is mapped over a wide range of dose rates. This dependence is very different from analogous MOSFET curves. Annealing experiments following irradiation show negligible change in base current at room temperature, but significant recovery at temperatures of 100 degrees C and above. In contrast to what is observed in MOSFETs, irradiation and annealing tests cannot be used to predict the low-dose-rate response of bipolar devices. A comparison of X-ray-induced and /sup 60/Co gamma-ray-induced gain degradation for bipolar transistors is reported. The role of the emitter bias during irradiation is also examined. Preliminary field-oxide capacitor studies suggest that the mechanism for the dose-rate effect may be related to charge yield in the basic surface oxides. Recommendations for hardness-assurance testing of bipolar devices include testing at dose rates below 10 rad(SiO/sub 2/)/s and applying safety factors to estimate the space-environment response.<
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