Proton tolerance of fourth-generation 350 GHz UHV/CVD SiGe HBTs

We report, for the first time, the impact of proton irradiation on fourth-generation SiGe heterojunction bipolar transistors (HBTs) having a record peak unity gain cutoff frequency of 350 GHz. The implications of aggressive vertical scaling on the observed proton tolerance is investigated through comparisons of the pre-and post-radiation ac and dc figures-of-merit to observed results from prior SiGe HBT technology nodes irradiated under identical conditions. In addition, transistors of varying breakdown voltage are used to probe the differences in proton tolerance as a function of collector doping. Our findings indicate that SiGe HBTs continue to exhibit impressive total dose tolerance, even at unprecedented levels of vertical profile scaling and frequency response. Negligible total dose degradation in [beta] (0.3%), [[Florin].sub.T] and [[Florin].sub.max] (6%) are observed in the circuit bias regime, suggesting that SiGe HBT BiCMOS technology is potentially a formidable contender for high-performance space-borne applications. Index Terms--Breakdwon voltage, heterojunction bipolar transistors (HBT), proton tolerance, SiGe, silicon-germanium, technology scaling.