A very small slice of silicon, a few millimetres square, on which many electronic circuits containing many components are built; also called an integrated circuit. Silicon chips are reliable and cheap to produce in large numbers (although the manufacturing process is very complex), and they are now used in computers, calculators, many modern programmed household appliances, and in most electronic applications. They have been a major factor in the microminiaturization of devices: a computer which once filled a large room can now be made on one small silicon chip.
A monolithic integrated circuit (also known as IC, microchip, silicon chip, computer chip or chip) is a miniaturized electronic circuit (consisting mainly of semiconductor devices, as well as passive components) that has been manufactured in the surface of a thin substrate of semiconductor material.
A hybrid integrated circuit is a miniaturized electronic circuit constructed of individual semiconductor devices, as well as passive components, bonded to a substrate or circuit board.
This article is about monolithic integrated circuits.
Introduction
Integrated circuits were made possible by experimental discoveries which showed that semiconductor devices could perform the functions of vacuum tubes, and by mid-20th-century technology advancements in semiconductor device fabrication. The integration of large numbers of tiny transistors into a small chip was an enormous improvement over the manual assembly of circuits using discrete electronic components. The integrated circuit's mass production capability, reliability, and building-block approach to circuit design ensured the rapid adoption of standardized ICs in place of designs using discrete transistors.
There are two main advantages of ICs over discrete circuits: cost and performance.
Advances in integrated circuits
Among the most advanced integrated circuits are the microprocessors, which control everything from computers to cellular phones to digital microwave ovens. Digital memory chips are another family of integrated circuit that is crucially important to the modern information society. While the cost of designing and developing a complex integrated circuit is quite high, when spread across typically millions of production units the individual IC cost is minimized.
ICs have consistently migrated to smaller feature sizes over the years, allowing more circuitry to be packed on each chip. This increased capacity per unit area can be used to decrease cost and/or increase functionality—see Moore's law which, in its modern interpretation, states that the number of transistors in an integrated circuit doubles every two years.
Popularity of ICs
Only a half century after their development was initiated, integrated circuits have become ubiquitous. That is, modern computing, communications, manufacturing and transport systems, including the Internet, all depend on the existence of integrated circuits. Indeed, many scholars believe that the digital revolution brought about by integrated circuits was one of the most significant occurrences in the history of mankind.
Classification
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, and other circuits 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.
Analog ICs, such as sensors, power management circuits, and operational amplifiers, work by processing continuous signals. Analog ICs ease the burden on circuit designers by having expertly designed analog circuits available instead of designing a difficult analog circuit from scratch.
ICs can also combine analog and digital circuits on a single chip to create functions such as A/D converters and D/A converters. Such circuits offer smaller size and lower cost, but must carefully account for signal interference (see signal integrity).
Manufacture
Fabrication
Main article: Semiconductor fabrication.
The semiconductors of the periodic table of the chemical elements were identified as the most likely materials for a solid state vacuum tube by researchers like William Shockley at Bell Laboratories starting in the 1930s. Today, silicon monocrystals are the main substrate used for integrated circuits (ICs) although some III-V compounds of the periodic table such as gallium arsenide are used for specialised applications like LEDs, lasers, and the highest-speed integrated circuits.
Semiconductor ICs are fabricated in a layer process which includes these key process steps:
Imaging Deposition EtchingThe main process steps are supplemented by doping, cleaning and planarisation steps.
Mono-crystal silicon wafers (or for special applications, silicon on sapphire or gallium arsenide wafers) are used as the substrate. The criss-crossed checkerboard-like (see image above) transistors are the most common part of the circuit, each checker forming a transistor.
A (random access memory) is the most regular type of integrated circuit;
Each device is tested before packaging using very expensive automated test equipment (ATE), a process known as wafer testing, or wafer probing. Silicon on insulator (SOI) Strained silicon in a process used by IBM known as Strained silicon directly on insulator (SSDOI)
Packaging
The earliest integrated circuits were packaged in ceramic flat packs, which continued to be used by the military for their reliability and small size for many years. Commercial circuit packaging quickly moved to the dual in-line package (DIP), first in ceramic and later in plastic. In the 1980s pin counts of VLSI circuits exceeded the practical limit for DIP packaging, leading to pin grid array (PGA) and leadless chip carrier (LCC) packages. Surface mount packaging appeared in the early 1980s and became popular in the late 1980s, using finer lead pitch with leads formed as either gull-wing or J-lead, as exemplified by Small-Outline Integrated Circuit.
Small-Outline Integrated Circuit (SOIC) and PLCC packages.
Traces out of the die, through the package, and into the printed circuit board have very different electrical properties, compared to on-chip signals. The boundary between a big MCM and a small printed circuit board is sometimes fuzzy.
History, origins and generations
The birth of the IC
The integrated circuit was first conceived by a radar scientist, Geoffrey W.A.
The first integrated circuits were manufactured independently by two scientists: Jack Kilby of Texas Instruments filed a patent for a "Solid Circuit" made of germanium on February 6, 1959. Robert Noyce of Fairchild Semiconductor was awarded a patent for a more complex "unitary circuit" made of Silicon on April 25, 1961. (See the Chip that Jack built for more information.)
Noyce credited Kurt Lehovec of Sprague Electric for the principle of p-n junction isolation caused by the action of a biased p-n junction (the diode) as a key concept behind the IC.
SSI, MSI, LSI
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.
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).
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.
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
Main article: Very-large-scale integration.
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).
For the first time it became possible to fabricate a CPU on a single integrated circuit, to create a microprocessor.
This step was largely made possible by the codification of "design rules" for the CMOS technology used in VLSI chips, which made production of working devices much more of a systematic endeavour. (See the 1980 landmark text by Carver Mead and Lynn Conway referenced below.)
ULSI, WSI, SOC
To reflect further growth of the complexity, the term ULSI that stands for "Ultra-Large Scale Integration" was proposed for chips of complexity more than 1 million of transistors.
The most extreme integration technique is wafer-scale integration (WSI), which uses whole uncut wafers containing entire computers (processors as well as memory).
The WSI technique failed commercially, but advances in semiconductor manufacturing allowed for another attack on IC complexity, known as System-on-Chip (SOC) design. In this approach, components traditionally manufactured as separate chips to be wired together on a printed circuit board are designed to occupy a single chip that contains memory, microprocessor(s), peripheral interfaces, Input/Output logic control, data converters, and other components, together composing the whole electronic system.
Other developments
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. 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.
The techniques perfected by the integrated circuits industry over the last three decades have been used to create microscopic machines, known as MEMS.
Silicon Graffiti
Ever since ICs were created, some chip designers have used the silicon surface area for surreptitious, non-functional images or words.
Key industrial and academic data
Notable ICs
The 555 common multivibrator subcircuit (common in electronic timing circuits) The 741 operational amplifier 7400 series TTL logic building blocks 4000 series, the CMOS counterpart to the 7400 series Intel 4004, the world's first microprocessor The MOS Technology 6502 and Zilog Z80 microprocessors, used in many home computersManufacturers
A list of notable manufacturers; acquired parts of Tseng Labs in 1997) Atmel (co-founded by ex-Intel employee) Broadcom Commodore Semiconductor Group (formerly MOS Technology) Cypress Semiconductor Fairchild Semiconductor (founded by ex-Shockley Semiconductor employees: the "Traitorous Eight") Freescale Semiconductor (formerly part of Motorola) GMT Microelectronics (formerly Commodore Semiconductor Group) Hitachi IBM (International Business Machines) Infineon Technologies (formerly part of Siemens) Intel (founded by ex-Fairchild employees) Intersil (formerly Harris Semiconductor) Lattice Semiconductor Linear Technology LSI Logic (founded by ex-Fairchild employees) Maxim IC Marvell Technology Group MicroSystems International MOS Technology (founded by ex-Motorola employees) Mostek (founded by ex-Texas Instruments employees) National Semiconductor (aka "NatSemi"; now owned by TPG)
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