An integrated circuit is the name for collections of electronic components imbedded onto a single piece of silicon. Silicon is the base for most transistors, diodes and other semiconductors. It can also be used as a resistor, capacitor and coil.
Each IC is designed to carry out certain tasks and the circuit is designed accordingly. The circuit is then printed or etched onto the silicon substrate and then into a plastic or ceramic enclosure.
Applications for integrated circuits are as varied as the imagination of the designers. Within limits, anything that can be designed and built with discrete components can be put into an IC. Audio amplifier, video processors, logic, memory, switches, radio frequency encoders and decoders are just a few examples. The range of IC applications is vast and growing daily. One of the major applications is computing. Computers that once had thousands of transistors have been reduced to a handful of ICs. The early computers that were the size of a building are now outperformed in almost every way by laptops and even handheld computers because of the use if ICs
As ICs are developed, the design costs and production costs of equipment are reducing. Reliability increases as large parts of the final product are enclosed in single packages, reducing assembly errors, connection problems and size of circuit boards.
It is now rare to see any electronic equipment that does not have at least one IC. Indeed, some have only one IC and require no other components of any kind. The real answer to the question is to look around. Wherever electronics are used, there is probably an IC inside
Many integrated circuits can be found in almost every electronic device. They function as timers,
amplifiers, logic units, counters, calculators, temperature sensors, and radio receivers.
Integrated circuit of Atmel Diopsis 740System on Chip showing memory blocks, logic and input/output pads around the periphery
Microchips (EPROM memory) with a transparent window, showing the integrated circuit inside. Note the fine silver-colored wires that connect the integrated circuit to the pins of the package. The window allows the memory contents of the chip to be erased, by exposure to strong ultraviolet light in an eraser device.
In electronics, an integrated circuit (also known as IC, chip, or microchip) 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. Integrated circuits are used in almost all electronic equipment in use today and have revolutionized the world of electronics. Computers, cellular phones, and other digital appliances are now inextricable parts of the structure of modern societies, made possible by the low cost of production of integrated circuits.
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. A monolithic integrated circuit is made of devices manufactured by diffusion of trace elements into a single piece of semiconductor substrate, a chip.
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 electronic components. The integrated circuit’s mass production capability, reliability, and building-block approach to design ensured the rapid adoption of standardized ICs in place of designs using discrete transistors.
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There are two main advantages of ICs over discrete circuits: cost and performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography and not constructed as one transistor at a time. Furthermore, much less material is used to construct a circuit as a packaged IC die than as a discrete circuit. Performance is high since the components switch quickly and consume little power (compared to their discrete counterparts) because the components are small and close together. As of 2006, chip areas range from a few square millimeters to around 350 mm2, with up to 1 million transistors per mm2.
The integrated circuit was invented in 1958 by Jack Kirby (1923-2005), an American engineer. In 2000, he won the Nobel Prize in physics for his integrated circuit. This basic design has evolved over the last half century to reach the level of the modern computer chip, which has millions of transistors on a thumbnail size piece of silicon.
SSI, MSI and LSI
The first integrated circuits contained only a few transistors. Called “Small-Scale Integration” (SSI), digital circuits containing transistors numbering in the tens provided a few logic gates for example, while early linear ICs such as the Plessey SL201 or the Philips TAA320 had as few as two transistors. The term Large Scale Integration was first used by IBM scientist Rolf Landauer when describing the theoretical concept, from there came the terms for SSI, MSI, VLSI, and ULSI.
SSI circuits were crucial to early aerospace projects, and vice-versa. Both the Minuteman missile and Apollo program needed lightweight digital computers for their inertial guidance systems; the Apollo guidance computer led and motivated the integrated-circuit technology[, while the Minuteman missile forced it into mass-production. The Minuteman missile program and various other Navy programs accounted for the total $4 million integrated circuit market in 1962, and by 1968, U.S. Government space and defense spending still accounted for 37% of the $312 million total production. The demand by the U.S. Government supported the nascent integrated circuit market until costs fell enough to allow firms to penetrate the industrial and eventually the consumer markets. The average price per integrated circuit dropped from $50.00 in 1962 to $2.33 in 1968. Integrated Circuits began to appear in consumer products by the turn of the decade, a typical application being FM inter-carrier sound processing in television receivers.
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.
Integrated circuits such as 1K-bit RAMs, calculator chips, and the first microprocessors, that began to be manufactured in moderate quantities in the early 1970s, had under 4000 transistors. True LSI circuits, approaching 10000 transistors, began to be produced around 1974, for computer main memories and second-generation microprocessors.
Main article: Very-large-scale integration
Upper interconnect layers on an Intel 80486DX2 microprocessor die.
The final step in the development process, starting in the 1980s and continuing through the present, was “very large-scale integration” (VLSI). The development started with hundreds of thousands of transistors in the early 1980s, and continues beyond several billion transistors as of 2009.
Multiple developments were required to achieve this increased density. Manufacturers moved to smaller rules and cleaner fabs, so that they could make chips with more transistors and maintain adequate yield. The path of process improvements was summarized by the International Technology Roadmap for Semiconductors (ITRS). Design tools improved enough to make it practical to finish these designs in a reasonable time. The more energy efficient CMOS replaced NMOS and PMOS, avoiding a prohibitive increase in power consumption. Better texts such as the landmark textbook by Mead and Conway helped schools educate more designers, among other factors.
In 1986 the first one megabit RAM chips were introduced, which contained more than one million transistors. Microprocessor chips passed the million transistor mark in 1989 and the billion transistor mark in 2005. The trend continues largely unabated, with chips introduced in 2007 containing tens of billions of memory transistors .
ULSI, WSI, SOC and 3D-IC
To reflect further growth of the complexity, the term ULSI that stands for “ultra-large-scale integration” was proposed for chips of complexity of more than 1 million transistors.
Wafer-scale integration (WSI) is a system of building very-large integrated circuits that uses an entire silicon wafer to produce a single “super-chip”. Through a combination of large size and reduced packaging, WSI could lead to dramatically reduced costs for some systems, notably massively parallel supercomputers. The name is taken from the term Very-Large-Scale Integration, the current state of the art when WSI was being developed.
A system-on-a-chip (SoC or SOC) is an integrated circuit in which all the components needed for a computer or other systems are included on a single chip. The design of such a device can be complex and costly, and building disparate components on a single piece of silicon may compromise the efficiency of some elements. However, these drawbacks are offset by lower manufacturing and assembly costs and by a greatly reduced power budget: because signals among the components are kept on-die, much less power is required (see Packaging).
A three-dimensional integrated circuit (3D-IC) has two or more layers of active electronic components that are integrated both vertically and horizontally into a single circuit. Communication between layers uses on-die signaling, so power consumption is much lower than in equivalent separate circuits. Judicious use of short vertical wires can substantially reduce overall wire length for faster operation
A CMOS 4000 IC in a DIP
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. These digital ICs, typically microprocessors, DSPs, and micro controllers work using binary mathematics to process “one” and “zero” signals.
Analog ICs, such as sensors, power management circuits, and operational amplifiers, work by processing continuous signals. They perform functions like amplification, active filtering, demodulation, mixing, etc. 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.
Rendering of a small cell with three metal layers (dielectric has been removed). The sand-colored structures are metal interconnect, with the vertical pillars being contacts, typically plugs of tungsten. The reddish structures are polysilicon gates, and the solid at the bottom is the crystalline silicon bulk.
Schematic structure of a CMOS chip, as built in the early 2000s. The graphic shows LDD-MISFET’s on an SOI substrate with five metallization layers and solder bump for flip-chip bonding. It also shows the section for FEOL (front-end of line), BEOL (back-end of line) and first parts of back-end process.
The semiconductors of the periodic table of the chemical elements were identified as the most likely materials for a state vacuum. Starting with copper oxide, proceeding to germanium, then silicon, the materials were systematically studied in the 1940s and 1950s. Today, silicon mono crystals 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 specialized applications like LEDs, lasers, solar cells and the highest-speed integrated circuits. It took decades to perfect methods of creating crystals without defects in the crystalline structure of the semiconducting material.
Semiconductor ICs are fabricated in a layer process which includes these key process steps:
The main process steps are supplemented by doping and cleaning.
Mono-crystal silicon wafers (or for special applications, silicon on sapphire or gallium arsenide wafers) are used as the substrate. Photolithography is used to mark different areas of the substrate to be doped or to have polysilicon, insulators or metal (typicallyaluminium) tracks deposited on them.
Integrated circuits are composed of many overlapping layers, each defined by photolithography, and normally shown in different colors. Some layers mark where various dopants are diffused into the substrate (called diffusion layers), some define where additional ions are implanted (implant layers), some define the conductors (polysilicon or metal layers), and some define the connections between the conducting layers (via or contact layers). All components are constructed from a specific combination of these layers.
In a self-aligned CMOS process, a transistor is formed wherever the gate layer (polysilicon or metal) crosses a diffusion layer.
Capacitive structures, in form very much like the parallel conducting plates of a traditional electrical capacitor, are formed according to the area of the “plates”, with insulating material between the plates. Capacitors of a wide range of sizes are common on ICs.
Meandering stripes of varying lengths are sometimes used to form on-chip resistors, though most logic circuits do not need any resistors. The ratio of the length of the resistive structure to its width, combined with its sheet resistivity, determines the resistance.
More rarely, inductive structures can be built as tiny on-chip coils, or simulated by gyrators.
Since a CMOS device only draws current on the transition between logic states, CMOS devices consume much less current than bipolar devices.
A random access memory is the most regular type of integrated circuit; the highest density devices are thus memories; but even a microprocessor will have memory on the chip. (See the regular array structure at the bottom of the first image.) Although the structures are intricate – with widths which have been shrinking for decades – the layers remain much thinner than the device widths. The layers of material are fabricated much like a photographic process, although light waves in the visible spectrum cannot be used to “expose” a layer of material, as they would be too large for the features. Thus photons of higher frequencies (typically ultraviolet) are used to create the patterns for each layer. Because each feature is so small, electron microscopes are essential tools for a process engineer who might be debugging a fabrication process.
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Each device is tested before packaging using automated test equipment (ATE), in a process known as wafer testing, or wafer probing. The wafer is then cut into rectangular blocks, each of which is called a die. Each good die (plural dice, dies, or die) is then connected into a package using aluminum (or gold) bond wires which are welded and/or Thermo sonic to pads, usually found around the edge of the die. After packaging, the devices go through final testing on the same or similar ATE used during wafer probing. Test cost can account for over 25% of the cost of fabrication on lower cost products, but can be negligible on low yielding, larger, and/or higher cost devices.
As of 2005, a fabrication facility (commonly known as a semiconductor lab) costs over $1 billion to construct, because much of the operation is automated. The most advanced processes employ the following techniques:
The wafers are up to 300 mm in diameter (wider than a common dinner plate).
Use of 65 nanometer or smaller chip manufacturing process. Intel, IBM, NEC, and AMD are using 45 nanometers for their CPU chips. IBM and AMD are development of a 45 nm process using immersion lithography.
Copper interconnects where copper wiring replaces aluminum for interconnects.
Low-K dielectric insulators.
Silicon on insulator (SOI)
Strained silicon in a process used by IBM known as strained silicon directly on insulator (SSDOI)
The 555 common multivibrator sub-circuit (common in electronic timing circuits)
The 741 operational amplifier
7400 series TTL logic building blocks
4000 series, the CMOS counterpart to the 7400 series (see also: 74HC00 series)
Intel 4004, the world’s first microprocessor, which led to the famous 8080 CPU and then the IBM PC’s 8088, 80286, 486 etc.
The MOS Technology 6502 and Zilog Z80 microprocessors, used in many home computers of the early 1980s
The Motorola 6800 series of computer-related chips, leading to the 68000 and 88000 series (used in some Apple computers and in the 1980s Commodore Amiga series).
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