ABSTRACT
SiGe heterojunction bipolar transistors now have performance that rivals the III-Vs and in many cases is
superior to them. This technology has grown to be a pervasive technology found in many products, not
solely because of the performance, but primarily because it is realized as a BiCMOS technology such that
very highly integrated product designs are possible by leveraging a base CMOS technology, which
already has existing libraries and intellectual property (IP). Additionally, passives and extensive RF-
analog enablement are also added to make custom designs possible that can be merged with the highly
integrated digital CMOS section. This combination of the performance of the HBT with all the large
digital integration capability is based on having the HBT structure and process fully integrated into the
base CMOS process such that it guarantees the compatibility of the HBT and CMOS. This will be the
central theme of this section on device structures and BiCMOS integration. The structures will always be
seen as within the context of a BiCMOS process. This chapter will begin with a review of the structures
that are used in SiGe heterojunction bipolar transistors broadly breaking them up into different types.
This will include an extensive section on transistor features, which will emphasize that what the final
device looks like is a combination of the bipolar structure and the intended applications. It will then
review BiCMOS integration flows followed by a section on the issues in integrating SiGe HBTs into
advanced CMOS processes. The chapter will conclude by looking at the performance limits and what
very advanced HBT structures might look like.
