Characterization of intra device mutual thermal coupling in multi finger SiGe:C HBTs

This paper studies the mutual coupling in trench isolated multi-emitter bipolar transistors fabricated in a Si/SiGe:C HBT technology STMicroelectronics featuring f_T and f_max of ~300GHz and ~400GHz, respectively. Thermal coupling parameters are extracted using three-dimensional (3D) thermal TCAD simulations. The obtained parameters are implemented in a distributed transistor model that considers self-heating as well as thermal coupling between emitter fingers. Very good agreement is achieved between circuit simulations and DC measurements carried out on an in-house designed test structure.