In-situ recovery of the base current of SiGe NPN HBTs at high gamma dose levels

The base current Ib of a 0.13 μm SiGe HBT (Heterojunction Bipolar Transistor) is measured during gamma irradiation. Three different regions are observed: an initial degradation region (0-20 kGy) in which Ib decreases, a saturation region (20-60 kGy), showing a saturation of Ib, and a recovery region (60-100 kGy) where the excess Ib starts to decrease. This technology is compared with two older technologies: a 0.35 μm SiGe HBT from AMS and a discrete transistor from Infineon. Both technologies show, after an initial increase in Ib a slight decrease of Ib. It is observed that the end of the initial degradation shifts to a lower dose as technology scales down.