INTEGRATED CIRCUIT

(IC) also called Microcircuit an assembly of electronic components, fabricated as a single unit, in which active semiconductor devices (transistors and diodes) and passive devices (capacitors and resistors) and their interconnections are built up on a chip of material called a substrate (most commonly made of silicon). The circuit thus consists of a unitary structure with no connecting wires. The individual circuit elements are microscopic in size. During World War II the need to reduce the size of electronic equipment spurred engineers to study methods of miniaturizing circuit construction. Printing was used for the first time in circuit construction; electronic parts mounted on a ceramic block were connected by printed patterns etched in a metal foil bonded to the block. The invention of the transistor in 1947 revolutionized electronic circuits in a number of ways. It was not only the first solid-state device capable of amplification, but it also demonstrated some of the vast potential of semiconductors. It could also be made extremely small. Transistors were quickly adopted for use in printed circuitry. The first circuit in which at least one element was contained within the substrate itself, called a monolithic integrated circuit, was demonstrated in 1958. By the end of the decade the basic techniques and equipment for circuit integration were available. Early ICs consisted of about 10 individual components on a silicon chip 3 mm (0.12 inch) square. The development of large-scale integration (LSI) during the early 1970s made it possible to pack thousands of transistors and other components on a chip of roughly the same size. This technology gave rise to the microprocessor, an IC that contains all the arithmetic, logic, and control circuitry needed to carry out the functions of a digital computer's central processing unit. Very large-scale integration (VLSI), developed during the 1980s, has vastly increased the circuit density of microprocessors (as well as of memory and support chips). This technology has yielded microprocessors containing more than 20,000,000 transistors on a chip less than 2 cm (0.79 inch) square. There are several types of integrated circuits. Monolithic integrated circuits, also called semiconductor, or silicon integrated, circuits, are formed by the superposition of layers of materials in various patterns to form a single, three-dimensional block of circuitry. The circuit elements are formed by the particular patterns and topology of conducting, semiconducting, and insulating layers that have been used in building up the structure. The range of electronic functions that can be performed by integrated circuits is vast and includes digital circuits, such as the logic circuits used in computers, and analog circuits, such as those used in amplifiers. In many areas of application, the performance of integrated circuitry is far superior to that of conventional circuits. Because of their small size, low power requirements and heat generation, modest cost, reliability, and speed of operation, they make possible electronic systems that would otherwise be impractical. Most important, computer technology would be severely restricted without the capabilities of integrated circuits. Integrated circuitry continues to grow in sophistication and complexity even as it shrinks in size. Cost effectiveness and mass production have made the technology available to all levels of the electronics industry. The revolution in consumer electronics, manifested in the enormous popularity of such devices as self-focusing cameras, programmable microwave ovens, and personal computers, would have been unthinkable without integrated circuitry. (IC), also called microcircuit, an assembly of electronic components, fabricated as a single unit, in which active semiconductor devices (transistors and diodes) and passive devices (capacitors and resistors) and their interconnections are built up on a chip of material called substrate. The circuit thus consists of a unitary structure with no connecting wires. The individual circuit elements are microscopic in size. All elements of integrated circuits are fabricated in situ by an iterative process of lithographic definition, deposition, and etching on the common substrate (in most cases, silicon) in such a manner that the resulting interconnected elements perform the desired electrical circuit function. Many ICs, typically about 1.5 square centimetres each, are fabricated simultaneously on silicon wafers up to 25 centimetres in diameter and subsequently sawed into individual chips (dies) prior to packaging. An IC thus produced is usually sealed in a plastic package with electrical leads that are internally connected by fine wires to output pads on the silicon die and that permit the packaged IC to be attached to a circuit card. The integration of a large number of semiconductor devices on a single die of silicon is made possible by the high operational efficiency of the individual devices. Because of this, power dissipation is minimal and so too are the requirements for heat removal. The result is an IC of high dependability, which is further enhanced by the process of integration itself because the method of manufacturing the electrical interconnections between the devices and circuit elements by metal deposition and etching yields an extremely dependable circuit structure. The number of devices integrated on a single tiny chip has increased from an initial few to nearly 100,000,000 as circuit elements with ever-smaller features are employed. This has, in turn, led to a progressive increase in complexity, as exemplified by the metal-oxide-semiconductor (MOS), the dynamic random-access memory (DRAM), and the MOS microprocessor. Since manufacturing cost is proportional to area, the use of smaller features has not only led to an increase in complexity and resulting functionality but also has produced a decrease in cost per transistor and an increase in circuit performance. There are two reasons for the latter: (1) the performance of the individual active devices improves as their internal dimensions become smaller; and (2) the quality of the performance of the entire circuit improves as the active devices are positioned closer to one another. Large-volume applications for ICs have further lowered the manufacturing costs per IC. The cumulative result is that the integrated circuit has become the most pervasive technology of the 20th century. It has provided the cornerstone of modern microelectronics and has promoted the development of the so-called information society. Applications of ICs range from their use in supercomputerswhich are bringing about revolutionary advances in medical diagnosis, biotechnology, aeronautical and space engineering, telecommunications, and defense systemsto the development of new consumer products capable of bringing services and information to the home and office environment that otherwise would not have been possible. Additional reading Overviews are presented in Gnter Friedrichs and Adam Schaff (eds.), Microelectronics and Society: For Better or for Worse (1982); in T.R. Reid, The Chip: How Two Americans Invented the Microchip and Launched a Revolution (1984, also published as Microchip: The Story of a Revolution and the Men Who Made It, 1985); and in a series of articles in Scientific American, vol. 237, no. 3 (September 1977). Integrated-circuit design is discussed in Arthur B. Glaser and Gerald E. Subak-Sharpe, Integrated Circuit Engineering: Design, Fabrication, and Applications (1977); Paul R. Gray and Robert G. Meyer, Analysis and Design of Analog Integrated Circuits, 3rd ed. (1993); Texas Instruments Incorporated, Linear Circuits Data Book (1984); L.J. Herbst, Monolithic Integrated Circuits: Techniques and Capabilities (1985); Richard S. Muller and Theodore I. Kamins, Device Electronics for Integrated Circuits, 2nd ed. (1986); and David A. Hodges and Horace G. Jackson, Analysis and Design of Digital Integrated Circuits, 2nd ed. (1988). Very-large-scale integration (VLSI) systems are treated in Carver Mead and Lynn Conway, Introduction to VLSI Systems (1980); Norman G. Einspruch (ed.), VLSI Electronics: Microstructure Science (1981 ); Norman G. Einspruch, VLSI Handbook (1985); Neil H.E. Weste and Kamran Eshraghian, Principles of CMOS VLSI Design: A Systems Perspective, 2nd ed. (1993); and Paul Losleben (ed.), Advanced Research in VLSI (1987), conference proceedings. Two useful articles in Proceedings of the IEEE are William C. Holton and Ralph K. Cavin III, A Perspective on CMOS Technology Trends, 74(12):16461668 (December 1986); and Morton E. Jones, William C. Holton, and Robert Stratton, Semiconductors: The Key to Computational Plenty, 70(12):13801409 (December 1982). Fabrication of integrated circuits is presented in Ivor Brodie and Julius J. Muray, The Physics of Microfabrication (1982), a moderately detailed review; Sorab K. Ghandhi, VLSI Fabrication Principles, 2nd ed. (1994), a review on silicon and gallium arsenide fabrication technology; David J. Elliott, Microlithography: Process Technology for IC Fabrication (1986), a monograph on materials, processes, and equipment that are used in microfabrication; and William J. McClean (ed.), Status 1994: A Report on the Integrated Circuit Industry (1994). William Coffeen Holton