Thermal Analysis of Power SiGe Heterojunction Bipolar Transistor with Novel Segmented Multi-emitter Structure

An effective method for enhancing thermal stability of a multi-emitter power heterojunction bipolar transistor (HBT) has been presented. The method employs the segmented emitter structure rather than the traditional non-segmented structure to suppress the junction temperature rise and reduce the thermal resistance. A suitable thermal model, which includes various thermal resistances of the different components, is built for the segmented multi-emitter HBT. Using this model, the thermal simulation for a ten-finger power SiGe HBT with segmented emitter structure is performed by ANSYS software. Considering the precision of the simulation and the restriction of ANSYS software, this study proposes two steps simulation method: first substrate simulation and second active region simulation. The three-dimensional temperature distribution on emitter fingers is obtained. Compared with non-segmented structure, the maximum junction temperature, thermal resistance of the power HBT with improved structure is significantly lower as expected, and the thermal stability is enhanced.