Cryogenic Total Ionizing Dose Effects and Annealing Behaviors of SiGe HBTs

The total ionizing dose (TID) responses of 0.35 lm and 0.13 lm SiGe HBTs at liquid-nitrogen temperature (78 K) were investigated using 10 keV X-rays. For the first time, we compared the annealing behaviors of SiGe HBTs irradiated at 78 K and room temperature (297 K). The results reconfirm that SiGe HBTs have superior TID tolerance up to Mrad(Si) levels, and the current gain degradation of DUTs irradiated at 78 K is much less than those irradiated at 297 K. However, the 0.35μ m SiGe HBTs irradiated at 78 K show further degradation after room temperature annealing (RTA) due to the thermal activation of oxide charge migration and the long-term buildup of interface traps. The 0.13 lm SiGe HBTs irradiated at 78 K show minor change after RTA, which can be attributed to the competition between interface trap creation and annealing.