BiCMOS

Bipolar CMOS (BiCMOS) is a semiconductor technology that integrates two formerly separate semiconductor technologies, those of the bipolar junction transistor and the CMOS (complementary metal-oxide-semiconductor) gate, in a single integrated circuit device.
Bipolar junction transistors offer high speed, high gain, and low output resistance, which are excellent properties for high-frequency analog amplifiers, whereas CMOS technology offers high input resistance and is excellent for constructing simple, low-power logic gates. For as long as the two types of transistors have existed in production, designers of circuits utilizing discrete components have realized the advantages of integrating the two technologies; however, lacking implementation in integrated circuits, the application of this free-form design was restricted to fairly simple circuits. Discrete circuits of hundreds or thousands of transistors quickly expand to occupy hundreds or thousands of square centimeters of circuit board area, and for very high-speed circuits such as those used in modern digital computers, the distance between transistors (and the minimum capacitance of the connections between them) also makes the desired speeds grossly unattainable, so that if these designs cannot be built as integrated circuits, then they simply cannot be built.
This technology found application in amplifiers and analog power management circuits, and has some advantages in digital logic. BiCMOS circuits use the characteristics of each type of transistor most appropriately. Generally this means that high current circuits use metal–oxide–semiconductor field-effect transistors (MOSFETs) for efficient control, and portions of specialized very high performance circuits use bipolar devices. Examples of this include radio frequency (RF) oscillators, bandgap-based references and low-noise circuits.
The Pentium, Pentium Pro, and SuperSPARC microprocessors also used BiCMOS.
Disadvantages.
Many of the advantages of CMOS fabrication, for example, do not transfer directly to BiCMOS fabrication. An inherent difficulty arises from the fact that optimizing both the BJT and MOS components of the process is impossible without adding many extra fabrication steps and consequently increasing the process cost. Finally, in the area of high performance logic, BiCMOS may never offer the (relatively) low power consumption of CMOS alone, due to the potential for higher standby leakage current.
History.
In July 1968, Hung-Chang Lin and Ramachandra R. Iyer demonstrated an integrated bipolar-MOS (BiMOS) audio amplifier, combining bipolar junction transistor (BJT) and metal-oxide-semiconductor (MOS) technologies, at Westinghouse Electric Corporation. Lin and Iyer later demonstrated, with C.T. Ho, the first BiCMOS integrated circuit, combining BJT and complementary MOS (CMOS) technologies on a single integrated circuit, at Westinghouse in October 1968. In 1984, BiCMOS large-scale integration (LSI) was demonstrated by a Hitachi research team led by H. Higuchi, Goro Kitsukawa and Takahide Ikeda.
In the 1990s, modern integrated circuit fabrication technologies began to make commercial BiCMOS technology a reality. This technology rapidly found application in amplifiers and analog power management circuits.
A type of BiCMOS technology is bipolar-CMOS-DMOS (BCD) technology, which combines BiCMOS with DMOS (double-diffused MOS), a type of power MOSFET technology. BCD technology combines three semiconductor device fabrication processes on a power IC (power integrated circuit) chip: bipolar for precise analog functions, CMOS for digital design, and DMOS for power electronic and high-voltage elements. It was developed by ST Microelectronics in the mid-1980s. There are two types of BCD: high-voltage BCD and high-density BCD. They have a wide range of applications, such as silicon-on-insulator (SOI) BCD being used for medical electronics, automotive safety and audio technology.