On the Effect of Epi Base Thickness of SiGe HBTs in BiCMOS Process: A Quest for Device Leakage Optimization

We report some interesting observations on the junction leakage characteristics of SiGe heterojunction bipolar transistors (HBTs) in BiCMOS technology node when the thickness of cap at the emitter-base (E-B) junction and spacer at the collector-base (C-B) junction were varied from their original thicknesses of Process of Record (POR). While preserving the total intrinsic base width, our work shows a possible improvement in the transistor junction leakage and breakdown voltage, despite some trade-offs which could be reoptimised by making slight modifications to the process. Our study provides a holistic understanding of the complex interdependence between thickness modulations in the epitaxial base and device characteristics in advanced SiGe HBTs.