Thermal modeling of the non-linear thermal resistance of the SiGe HBT using the HICUM model

The existing industry standard compact models, VBIC and HICUM, are used to model devices using a linear thermal resistance network. However, the thermal resistance of the SiGe Heterojunction Bipolar Transistor (HBT) depends on the amount of power dissipated in the device. The increase of thermal resistance caused by self-heating due to the unsymmetrical emitter geometry and deep trenches lead to a non-linear relation between temperature and power dissipation. In this paper, a current controlled voltage source (CCVS) is used to account for the variation in current to model the thermal resistance of the device.