Future Directions in Germanium BiCMOS

The broadband data boom and associated evolving telecommunication standards are calling for high-performing devices with ever increasing circuit complexity. New high data-rate services are driving the use of higher operating frequencies on optical and wireless systems, while requiring greater chip integration, reduced power consumption and optimized costs.

New Microwave applications such as Automotive Radars (24/77GHz), Satellite Communications, LAN RF transceivers (60GHz), Point¬-to-Point radio (V-Band/E-Band), Defense, Security or Instrumentation are also extremely demanding of RF performance and operating conditions.

To support this demand, ST is investing aggressively in BiCMOS technology that provides the optimal answer for those needs.

The development of SiGe BiCMOS has mirrored silicon semiconductor development as the technology transitioned from Ge transistors, to silicon transistors, to ion-implanted base, to polysilicon emitter transistors, and finally to SiGe HBTs and SiGe BiCMOS. While the physics of the graded base SiGe HBT transistor was established early on in 1954 by Herb Kroemer it was not until the 1980s that SiGe HBTs were first realized. At the core of the SiGe Heterojunction Bipolar transistor development is the SiGe Epitaxy. In fact the SiGe HBT drove the development of the SiGe:B S/D processes now used for stressors in advanced CMOS since it was the first commercial technology with SiGe layers.BiCMOS: the best of two worlds 
BiCMOS combines the strengths of two different process technologies into a single chip: Bipolar transistors offer high speed and gain, which are critical for high-frequency analog sections, whereas CMOS technology excels for constructing simple, low-power logic gates.

By integrating the RF, analog and digital parts on a single chip, ST’s BiCMOS SiGe (Silicon-Germanium) technology drastically reduces the number of external components while optimizing power consumption.

ST’s BiCMOS process technology today offers a level of performance attainable in the recent past only with more expensive technologies such as gallium arsenide (GaAS), while providing a significant advantage in integration.

Compared to bulk CMOS, the BiCMOS Heterojunction Bipolar Transistor (HBT) allows a much higher cut-off frequency at a given technology node. To reach similar frequency, bulk CMOS designs have to use much smaller process nodes, forcing compromises on the design and leading most of the time to overall lower performance and higher cost.

Thus, thanks to its better cost profile compared to the alternatives, ST’s BiCMOS enables new business cases.

ST leads in BiCMOS process technology 
With strong know-how in design, architecture and process integration, STMicroelectronics offers a leading-edge SiGe BiCMOS technology, enabling the design of high-performance RF ICs.

SiGe HBT BiCMOS continues to find large volume production opportunities in applications that require mostly RF/Analog and less digital content (Big-A/little-D). Scaling has driven the speed performance (fMAX) towards terahertz levels to open up yet more applications. Many challenges still exist in the technology.