Integrated Bipolar Transistors Silicon Germanium BiCMOS Technologies

Bipolar transistors integrated with CMOS technologies have given rise to BiCMOS (bipolar/CMOS) technologies, which combine the advantages of bipolar transistors for analog and radio-frequency (RF) circuits with those of field-effect transistors (MOS) for digital functions. The main advantages of bipolar transistors over MOS transistors are higher gain (higher g _M transconductance and lower g _D output conductance), lower low-frequency noise, better voltage handling (at the same speed), and greater reliability. BiCMOS technologies fall into several families, which can be classified according to the voltage and frequency range covered, and ultimately the applications targeted. Technologies addressing high-voltage circuits generally integrate high-voltage DMOS (Drift MOS) transistors, and are therefore called BCD (bipolar/CMOS/DMOS). Technologies integrating complementary NPN and PNP bipolar transistors in CMOS technology are called C-BiCMOS (Complementary BiCMOS). They are used for specific circuits such as operational amplifiers. Finally, the technologies of particular interest in this article are the so-called "fast" BiCMOS technologies. They are mainly used in optical and wireless (RF) communications infrastructure networks, as well as for driver assistance radars. Their main feature is the integration of silicon (Si)/silicon germanium (SiGe) heterojunction NPN bipolar transistors (TBH). The operation and electrical characteristics of bipolar transistors, as well as the associated trade-offs, are explained first. The various transistor architectures, the state of the art in performance, and the challenges of frequency scaling are then presented. BiCMOS integration and, more specifically, the advantages and constraints of the CMOS node are discussed. Finally, a few examples of applications for fast BiCMOS technologies are reviewed, and the performance of the associated circuits is compared with those produced using other technologies.

At the end of the article, readers will find a glossary and a table of symbols used.