An Evaluation of Transistor-Layout RHBD Techniques for SEE Mitigation in SiGe HBTs

We investigate transistor-level layout-based techniques for SEE mitigation in advanced SiGe HBTs. The approach is based on the inclusion of an alternate reverse-biased pn junction (n-ring) designed to shunt electron charge away from the sub-collector to substrate junction. The inclusion of the n-ring affects neither the DC nor AC performance of the SiGe HBT and does not compromise its inherent multi-Mrad TID tolerance. The effects of ion strike location and angle of incidence, as well as n-ring placement, area, and bias on charge collection are investigated experimentally using a 36 MeV O₂ microbeam. The results indicate that charge shunting through the n-ring can result in up to a 90% reduction in collector collected charge for strikes outside the DT and a 18% reduction for strikes to the emitter center. 3-D transient strike simulations using NanoTCAD are used to verify the experimental observations, as well as shed insight into the underlying physical mechanisms. Circuit implications for this RHBD technique are discussed and recommendations made.