ABSTRACT
Advances in silicon–germanium (SiGe) heterojunction bipolar transistor (HBT) technologies resulted in an impressive increase in high-frequency performance during the last decade extending the addressed application frequencies into the mm- and sub-mm-wave bands. The reminder of this chapter is organized as follows. Major performance factors of SiGe HBTs are reviewed in the section “HBT Performance Factors.” The doping profiles of the non-depleted emitter and collector regions are optimized for low resistivity due to high concentrations of electrically active dopants. The lowest emitter resistances are typically achieved with mono-crystalline emitters. Contributions to the extrinsic base resistance originate from the extension of the base layer below the base–emitter spacer, from the adjacent monocrystalline or poly-crystalline p-doped region, the contact resistance between silicide and base poly-Si, the silicide resistance, the contact resistance between silicide and metal contact plug, as well as from the resistance of subsequent metal regions.
