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 (Dell XPS M1210 Battery) .
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 (Dell Studio XPS 1340 Battery) .
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 (Dell Studio XPS 1640 Battery) .
Synthetic detail of an integrated circuit through four layers of planarized copper interconnect, down to the polysilicon (pink), wells (greyish), and substrate (green).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 (Dell Vostro 1710 Battery) .
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 circuit design ensured the rapid adoption of standardized ICs in place of designs using discrete transistors (Sony VGP-BPS13 battery) .
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 rather than being constructed one transistor at a time. Furthermore, much less material is used to construct a packaged IC die than a discrete circuit (Sony VGP-BPS13/B battery) .
Performance is high since the components switch quickly and consume little power (compared to their discrete counterparts) because the components are small and positioned close together. As of 2006, chip areas range from a few square millimeters to around 350 mm2, with up to 1 milliontransistors per mm2 (Sony VGP-BPS13/S battery) .
Early developments of the integrated circuit go back to 1949, when the German engineer Werner Jacobi (Siemens AG) filed a patent for an integrated-circuit-like semiconductor amplifying device showing five transistors on a common substrate arranged in a 2-stage amplifier arrangement. Jacobi discloses small and cheap hearing aids as typical industrial applications of his patent (Sony VGP-BPS13A/B battery) .
A commercial use of his patent has not been reported.
The idea of the integrated circuit was conceived by a radar scientist working for the Royal Radar Establishment of the British Ministry of Defence, Geoffrey W.A. Dummer (1909–2002), who published it at the Symposium on Progress in Quality Electronic Components in Washington, D.C. on May 7, 1952 (Sony VGP-BPS13B/B battery) .
He gave many symposia publicly to propagate his ideas. Dummer unsuccessfully attempted to build such a circuit in 1956.
A precursor idea to the IC was to create small ceramic squares (wafers), each one containing a single miniaturized component. Components could then be integrated and wired into a bidimensional or tridimensional compact grid (Sony VGP-BPL9 battery) .
This idea, which looked very promising in 1957, was proposed to the US Army by Jack Kilby, and led to the short-lived Micromodule Program (similar to 1951's Project Tinkertoy). However, as the project was gaining momentum, Kilby came up with a new, revolutionary design: the IC (Sony VGP-BPL11 battery) .
Robert 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.
Jack Kilby recorded his initial ideas concerning the integrated circuit in July 1958 and successfully demonstrated the first working integrated circuit on September 12, 1958 (Sony VGP-BPL15 battery) .
In his patent application of February 6, 1959, Kilby described his new device as “a body of semiconductor material ... wherein all the components of the electronic circuit are completely integrated.” Kilby won the 2000 Nobel Prize in Physics for his part of the invention of the integrated circuit (Dell Inspiron E1505 battery) .
Robert Noyce also came up with his own idea of an integrated circuit half a year later than Kilby. Noyce's chip solved many practical problems that Kilby's had not. Noyce's chip, made at Fairchild Semiconductor, was made of silicon, whereas Kilby's chip was made of germanium (Dell Latitude E6400 battery) .
In the early days of integrated circuits, only a few transistors could be placed on a chip, as the scale used was large because of the contemporary technology. As the degree of integration was small, the design was done easily. Later on, millions, and today billions , of transistors could be placed on one chip, and to make a good design became a task to be planned thoroughly (HP Pavilion dv6000 Battery) .
This gave rise to new design methods.
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 (Sony Vaio VGN-FZ31S battery) .
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 (Sony VGN-FZ31S battery) .
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 (Hp pavilion dv6000 battery) .
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 (SONY VGN-FZ38M Battery) .
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) (SONY VGN-FZ31z Battery) .
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 (SONY VGN-FZ31E Battery) .
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 (SONY VGN-FZ31J Battery) .
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 (SONY VGN-FZ31M Battery) .
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) (SONY VGN-FZ31B Battery) .
Design tools improved enough to make it practical to finish these designs in a reasonable time. The more energy efficient CMOSreplaced 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 (SONY VGP-BPS13 Battery) .
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 (Dell Inspiron 1320 Battery) .
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" (Dell Inspiron 1320n Battery) .
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 (Dell Inspiron 1464 Battery) .
A system-on-a-chip (SoC or SOC) is an integrated circuit in which all the components needed for a computer or other system 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 (Dell Inspiron 1564 Battery) .
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 (Dell Inspiron 1764 Battery) .
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.
Advances in integrated circuits
The die from an Intel 8742, an 8-bitmicrocontroller that includes a CPUrunning at 12 MHz, 128 bytes of RAM, 2048 bytes of EPROM, and I/O in the same chip (Dell Studio 1450 Battery) .
Among the most advanced integrated circuits are the microprocessors or "cores", which control everything from computers and cellular phones to digitalmicrowave ovens. Digital memory chips and ASICs are examples of other families of integrated circuits that are important to the modern information society (Dell Studio 1457 Battery) .
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. The performance of ICs is high because the small size allows short traces which in turn allows low power logic (such as CMOS) to be used at fast switching speeds (Dell Latitude D610 Battery) .
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 (Toshiba NB100 Battery) .
In general, as the feature size shrinks, almost everything improves—the cost per unit and the switching power consumption go down, and the speed goes up. However, ICs with nanometer-scale devices are not without their problems, principal among which is leakage current (see subthreshold leakage for a discussion of this), although these problems are not insurmountable and will likely be solved or at least ameliorated by the introduction of high-k dielectrics (Toshiba Satellite M65 battery) .
Since these speed and power consumption gains are apparent to the end user, there is fierce competition among the manufacturers to use finer geometries. This process, and the expected progress over the next few years, is well described by the International Technology Roadmap for Semiconductors (ITRS) (Toshiba Satellite M60 battery) .
In current research projects, integrated circuits are also developed for sensoric applications in medical implants or other bioelectronic devices. Particular sealing strategies have to be taken in such biogenic environments to avoid corrosion or biodegradation of the exposed semiconductor materials. As one of the few materials well established in CMOStechnology, titanium nitride TiN turned out as exceptionally stable and well suited for electrode applications in medical implants (Dell Latitude D830 Battery) .
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 (Dell Studio 1735 Battery) .
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 (Dell Latitude D620 Battery) .
They perform functions likeamplification, 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 (Dell Inspiron Mini 10 Battery) .
Rendering of a small standard cellwith 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 (Sony VGN-FW11S Battery) .
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 (Sony VGN-FW11M Battery) .
The semiconductors of the periodic table of the chemical elements were identified as the most likely materials for a solid state vacuum tube. Starting with copper oxide, proceeding to germanium, then silicon, the materials were systematically studied in the 1940s and 1950s (Dell Studio 1555 battery) .
Today, silicon monocrystals are the mainsubstrate 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 (Dell Latitude E5400 Battery) .
Semiconductor ICs are fabricated in a layer process which includes these key process steps:
- Etching (Dell Latitude E4200 Battery)
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 (typically aluminium) tracks deposited on them (Dell Vostro A840 Battery) .
- 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) (Dell Inspiron 300M Battery) .
- 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 (Dell Studio 1737 battery) .
- 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 (Dell Inspiron E1505 battery) .
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 (Dell Latitude E6400 battery) .
(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 (Dell RM791 battery) .
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.
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 (Dell XPS M1530 battery) .
Each good die (plural dice, dies, or die) is then connected into a package using aluminium (or gold)bond wires which are welded and/or Thermosonic Bonded 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 (Dell XPS M2010 battery) .
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 (Dell Vostro 1000 battery) :
- 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 in development of a 45 nm process using immersion lithography.
- Copper interconnects where copper wiring replaces aluminium for interconnects (Acer Aspire One battery) .
- Low-K dielectric insulators.
- Silicon on insulator (SOI)
- Strained silicon in a process used by IBM known as strained silicon directly on insulator (SSDOI)
Early USSR-made integrated circuit (Toshiba Satellite P10 Battery)
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 (SONY VGN-FZ210CE Battery) .
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 bysmall-outline integrated circuit -- a carrier which occupies an area about 30 – 50% less than an equivalent DIP, with a typical thickness that is 70% less. This package has "gull wing" leads protruding from the two long sides and a lead spacing of 0.050 inches (Dell Precision M70 Battery) .
In the late 1990s, PQFP and TSOP packages became the most common for high pin count devices, though PGA packages are still often used for high-endmicroprocessors. Intel and AMD are currently transitioning from PGA packages on high-end microprocessors to land grid array (LGA) packages (Toshiba Satellite L305 Battery) .
Ball grid array (BGA) packages have existed since the 1970s. Flip-chip Ball Grid Array packages, which allow for much higher pin count than other package types, were developed in the 1990s. In an FCBGA package the die is mounted upside-down (flipped) and connects to the package balls via a package substrate that is similar to a printed-circuit board rather than by wires (Toshiba Satellite T4900 Battery) .
FCBGA packages allow an array of input-output signals (called Area-I/O) to be distributed over the entire die rather than being confined to the die periphery.
Traces out of the die, through the package, and into the printed circuit board have very different electrical properties, compared to on-chip signals (Toshiba PA3399U-2BRS battery) .
They require special design techniques and need much more electric power than signals confined to the chip itself.
When multiple dies are put in one package, it is called SiP, for System In Package. When multiple dies are combined on a small substrate, often ceramic, it's called an MCM, or Multi-Chip Module. The boundary between a big MCM and a small printed circuit board is sometimes fuzzy (Toshiba Satellite A200 Battery) .
Chip labeling and manufacture date
Most integrated circuits large enough to include identifying information include four common sections: the manufacturer's name or logo, the part number, a part production batch number and/or serial number, and a four-digit code that identifies when the chip was manufactured (Toshiba Satellite 1200 Battery) .
Extremely small surface mount technology parts often bear only a number used in a manufacturer's lookup table to find the chip characteristics.
The manufacturing date is commonly represented as a two-digit year followed by a two-digit week code, such that a part bearing the code 8341 was manufactured in week 41 of 1983, or approximately in October 1983 (Toshiba Satellite M300 Battery) .
Legal protection of semiconductor chip layouts
Main article: Semiconductor Chip Protection Act of 1984
Prior to 1984, it was not necessarily illegal to produce a competing chip with an identical layout. As the legislative history for the Semiconductor Chip Protection Act of 1984, or SCPA, explained, patent and copyright protection for chip layouts, or topographies, were largely unavailable (Dell Latitude XT2 Tablet PC Battery) .
This led to considerable complaint by U.S. chip manufacturers—notably, Intel, which took the lead in seeking legislation, along with the Semiconductor Industry Association (SIA)--against what they termed "chip piracy."
A 1984 addition to US law, the SCPA, made all so-called mask works (i.e., chip topographies) protectable if registered with the U.S. Copyright Office (Toshiba Portege 335CT Battery) .
Similar rules apply in most other countries that manufacture ICs. (This is a simplified explanation - see SCPA for legal details.)
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 (Dell Vostro A90 Battery) .
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 1.5 GHz (Achronix holding the speed record) (Toshiba Satellite P15 Battery) .
The techniques perfected by the integrated circuits industry over the last three decades have been used to create microscopic machines, known as MEMS. These devices are used in a variety of commercial and military applications. Example commercial applications include DLP projectors, inkjet printers, and accelerometers used to deploy automobile airbags (Toshiba Satellite Pro M10 Battery) .
In the past, radios could not be fabricated in the same low-cost processes as microprocessors. But since 1998, a large number of radio chips have been developed using CMOS processes. Examples include Intel's DECT cordless phone, or Atheros's 802.11 card.
Future developments seem to follow the multi-core multi-microprocessor paradigm, already used by the Intel and AMD dual-core processors (Toshiba Portege 3110 Battery) .
Intel recently unveiled a prototype, "not for commercial sale" chip that bears 80 microprocessors. Each core is capable of handling its own task independently of the others. This is in response to the heat-versus-speed limit that is about to be reached using existing transistor technology (Toshiba Portege R600 Battery) .
This design provides a new challenge to chip programming. Parallel programming languages such as the open-source X10 programming language are designed to assist with this task.
Silicon labelling and graffiti
To allow identification during production most silicon chips will have a serial number in one corner (Toshiba Satellite 1900 Battery) .
It is also common to add the manufacturer's logo. Ever since ICs were created, some chip designers have used the silicon surface area for surreptitious, non-functional images or words. These are sometimes referred to as Chip Art, Silicon Art, Silicon Graffiti or Silicon Doodling (Toshiba Portege R200 Battery) .