We present a study of thermal resistance in trench-isolated Si/SiGe heteroj
unction bipolar transistors (HBTs), using a technique based on isothermal c
ollector current measurement. Measured thermal resistance is in good agreem
ent with a realistic three-dimensional (3-D) numerical model; emitter metal
lization, shallow trenches, and heat flow through the deep trench walls are
all shown to have a significant effect on the thermal resistance.