Parasitic electrostatic capacitance of high-speed SiGe Heterojunction Bipolar Transistors

Vertical and horizontal scaling is aggressively used to increase frequency performances of SiGe Heterojunction Bipolar Transistors. As a result, the evaluation of the extrinsic electrostatic capacitances becomes increasingly important. In this article, we investigate the electrostatic parasitic capacitance in 230-335 GHz SiGe transistor technologies. We compare measured electrostatic capacitances with calculations based on a finite elements modelling. We conclude that the influence of the parasitic capacitances only screens the intrinsic performances of the devices by 10-14% but an accurate estimation of theses parasitics must be included in the design of next generation SiGe HBT.