Impact of Self-Heating in Si/SiGe HBTs with Multi-Finger Emitters

This study explores the static, dynamic, and thermal behaviors of SiGe Heterojunction Bipolar Transistors (HBTs) fabricated using the BiCMOS9MW 0.13 µm technology with varying multi-finger emitter configurations (1 to 12 emitters). Simulations conducted via COMSOL Multiphysics integrated the Semiconductor and Heat Transfer in Solids (HTS) modules. Results revealed substantial improvements in collector and base currents, along with an increase in maximum current gain (βmax) from 1913 to 3870, depending on the emitter count. The 12-emitter device achieved the highest cutoff (ft = 316.8 GHz) and oscillation frequencies (fmax = 360.1 GHz). Thermal analysis demonstrated that increasing emitter count reduces maximum self-heating temperatures (Tmax), dropping from 467 K for a singleemitter HBT to 413 K for a 12-emitter configuration. Central emitters experienced the highest temperatures due to thermal coupling. These findings provide key insights into optimizing emitter configurations to enhance performance and thermal stability in advanced BiCMOS technologies.