Study of mutual and self-thermal resistance in 90nm SiGe HBTs

Abstract

Impact of mutual thermal coupling on the performance of a single 90nm SiGe heterojunction bipolar transistor (HBT) due to the presence of power dissipating elements like other HBTs in near vicinity is presented in this paper. Mutual thermal resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th,mutual</sub> ) has been computed as a function of spacing between the single HBT and a ring of HBTs surrounding the device. HBT structural design variations including device layout schemes, metal wire stack connected to the emitter, deep trench (DT) depth and emitter to DT spacing, for reduced self thermal resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> ), have been explored in this paper. An updated thermal resistance model accounting for the heat flow through the metal wiring stack connected to the emitter is also reported.