Thermal Impedance Model for Multifinger SiGe HBTs

In this work, we propose a model for thermal impedance in multifinger SiGe HBTs. Our model utilizes a resistance-capacitance ladder in Cauver form to accurately capture the heat diffusion physics within and among the fingers under transient operating conditions. Notably, our approach directly incorporates transient thermal coupling into the self-heating thermal network, eliminating the need for conventional superposition techniques for nonlinear thermal coupling. Including thermal coupling information into the self-heating network significantly reduces the node count, which can result in improved simulation speed. We conduct 3D TCAD simulations using the STMicroelectronics B55 technology to validate our proposed model for five-finger SiGe HBTs.