Main Page | See live article | Alphabetical index An integrated circuit (IC) is a microelectronic semiconductor device consisting of many interconnected transistors and other components. SEM image Table of contents 1 Fabrication 2 Significance 3 History 3.1 SSI 3.2 MSI 3.3 LSI 3.4 VLSI 4 Further Developments 5 Notable Integrated Circuits 6 See also 7 References Fabrication Semiconductor device fabrication: ICs are constructed ("fabricated") on a single-crystal silicon "wafer" (or for special applications, silicon on sapphire or gallium arsenide wafers). This is known as the "substrate". Photolithography is used to mark different areas of the substrate to be doped or to have polysilicon or aluminum tracks sputtered on them. (See also semiconductor.) Each device is tested, before packaging. The wafer is then diced into small rectangles called die. The die is then connected into a package using gold or aluminum wires which are welded to "pads", usually found around the edge of the die. After packaging, the devices go through final test on very expensive automated testers, which account for over 25 percent of the cost of fabrication. A fabrication facility, commonly known as a fab, currently costs over a billion US Dollars to construct, because much of the operation is automated. In the most advanced processes, the wafers exceed 30 centimeters in diameter (wider than a common dinner plate). Significance Integrated circuits can be classified into analog, digital and mixed signal (both analog and digital on the same chip). Digital integrated circuits can contain anything from one to millions of logic gates, flip-flops, multiplexers, etc. in a few square millimeters. The small size of these circuits allows high speed, low power dissipation, and reduced manufacturing cost compared with board-level integration. The growth of complexity of integrated circuits follows a trend called "Moore's Law", first observed by Gordon Moore of Intel. Moore's Law states that the number of transistors in an integrated circuit doubles every two years. By the year 2000 the largest integrated circuits contained hundreds of millions of transistors, and the trend shows no signs of slowing down. The integrated circuit is one of the most important inventions of the 20th century. Modern computing, communications, manufacturing, and transportation systems, including the Internet, all depend on its existence. History The concept for the integrated circuit was first published by Geoffrey W.A. Dummer on May 7, 1952. The first integrated circuits were developed independently by two scientists: Jack Kilby of Texas Instruments filed a patent for a "Solid Circuit" on February 6, 1958, and Robert Noyce of Fairchild Semiconductor was awarded a patent for a more complex "unitary circuit" on April 25, 1961. Noyce credited Kurt Lehovec of Sprague Electric for the principle of dielectric isolation caused by the action of a p-n junction (the diode) as a key concept behind the IC. SSI The first integrated circuits contained only a few transistors. Called "Small-Scale Integration" (SSI), they used circuits containing transistors numbering in the tens. SSI circuits were crucial to early aerospace projects, and vice-versa. Both the Minuteman missile and Apollo program needed lightweight digital computers for their inertially-guided flight computers; the Apollo flight computer led and motivated the integrated-circuit technology, while the Minuteman missile forced it into mass-production. These programs purchased almost all of the available integrated circuits from 1960 through 1963, and almost alone provided the demand that funded the production improvements to get the production costs from $1000/circuit (in 1960 dollars) to merely $25/circuit (in 1963 dollars). MSI The next step in the development of integrated circuits, taken in the late 1960s, introduced devices which contained hundreds of transistors on each chip, called "Medium-Scale Integration" (MSI). They were attractive economically because while they cost little more to produce than SSI devices, they allowed more complex systems to be produced using smaller circuit boards, less assembly work (because of fewer separate components), and a number of other advantages. LSI Further development, driven by the same economic factors, led to "Large-Scale Integration" (LSI) in the mid 1970s, with tens of thousands of transistors per chip. LSI circuits began to be produced in large quantities around 1970, for computer main memories and pocket calculators. VLSI The final step in the development process, starting in the 1980s and continuing on, was "Very Large-Scale Integration" (VLSI), with hundreds of thousands of transistors, and beyond (well past several million in the latest stages). The largest chips are sometimes called "Ultra Large-Scale Integration" (ULSI). For the first time it became possible to fabricate a CPU or even an entire microprocessor on a single integrated circuit. In 1986 the first one megabyte RAM was introduced, which contained more than one million transistors. Microprocessor chips produced in 1994 contained more than three million transistors. This step was largely made possible by the codification ( see: Carver Mead and Lynn Conway) of "design rules" for the CMOS technology used in VLSI chips, which made production of working devices much more of a systematic endeavour. Further Developments The most extreme integration technique is wafer-scale integration (WSI), which uses whole uncut wafers containing entire computers (processors as well as memory). Attempts to take this step commercially in the 1980s (e.g. by Gene Amdahl) failed, and it does not now seem to be a high priority for industry. In the 1980s programmable integrated circuits were developed. These devices contain circuits whose logical function and connectivity can be programmed by the user, rather than being fixed by the integrated circuit manufacturer. This allows a single chip to be programmed to implement different LSI-type functions such as logic gates, adders and registers. Current devices named FPGAs (Field Programmable Gate Arrays) can now implement tens of thousands of LSI circuits in parallel and operate up to 400 MHz. Notable Integrated Circuits The 555 common multivibrator subcircuit (used in electronic timing circuits) The 741 operational amplifier 7400 series TTL logic building blocks 4000 series CMOS successors to the 7400 series Intel 4004, the world's first microprocessor The MOS 6502 microprocessor, used in many home computers See also Electronics Mixed-mode integrated circuit Transistor-transistor logic (TTL) Electrical engineering Computer engineering Microcontroller Simulation Sound chip SPICE, HDL, ZIF, ATPG References Mead, C. and Conway, L. (1980). Introduction to VLSI Systems. Addison-Wesley. ISBN 0-201-04358-0. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.