In this paper, we establish a three-dimensional numerical simulation model for SiGe heterojunction bipolar transistor by the technology computer aided design simulations. In the simulation we investigate the charge collection mechanism by heavy ion radiation in SiGe HBT technology. The results show that the charge collected by the terminals is a strong function of the ion striking position. The sensitive area of charge collection for each terminal is identified based on the analyses of the device structure and simulation results. For a normal strike within and around the area of the collector/substrate junction, most of the electrons and holes are collected by the collector and substrate terminals, respectively. For an ion strike between the shallow trench edges surrounding the emitter, the base collects a large quantity of charge, while the emitter collects a negligible quantity of charge.