SiGe Base Engineering in HBTs for Improving Breakdown and ICES Leakage Characteristics : YE: Yield Enhancement/ Learning

Silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) enabled reduced base widths and increased base doping due to bandgap engineering of the SiGe base. However, the base width is constrained by punch-through breakdown. The incorporation of SiGe with silicon forms a heterojunction, introducing strain into the SiGe or Si during fabrication. Fully strained SiGe layers are typically stable and free of dislocations post-growth. It is essential to produce high quality, strained SiGe base layers, as the carrier mobility in these layers is significantly enhanced compared to Si BJTs. However, a relaxed SiGe base layer is undesirable due to the presence of misfit dislocations, which act as generation-recombination centers, degrading leakage current performance. This paper outlines a strategy for improving breakdown voltage and ICES leakage characteristics in SiGe HBTs by optimizing the SiGe base dopant profile, thickness, and growth rate throughout the fabrication process.