In electronics, an integrated circuit also known as IC, microcircuit, microchip, silicon 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. Integrated circuits are used in almost all electronic equipment in use today and have revolutionized the world of electronics.
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.
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.
The idea of an 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. He gave many symposia publicly to propagate his ideas.
Dummer unsuccessfully attempted to build such a circuit in 1956.
The integrated circuit can be credited as being invented by both Jack Kilby of Texas Instruments and Robert Noyce of Fairchild Semiconductor working independently of each other. Kilby recorded his initial ideas concerning the integrated circuit in July 1958 and successfully demonstrated the first working integrated circuit on September 12, 1958. In his patent application of February 6, 1959, Kilby described his new device as ââ‚¬Å“a body of semiconductor material … wherein all the components of the electronic circuit are completely integrated.ââ‚¬
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Kilby won the 2000 Nobel Prize in Physics for his part of the invention of the integrated circuit. Robert Noyce also came up with his own idea of integrated circuit, half a year later than Kilby. Noyce’s chip had solved many practical problems that the microchip developed by Kilby had not. Noyce’s chip, made at Fairchild, was made of silicon, whereas Kilby’s chip was made of germanium.
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. A commercial use of his patent has not been reported.
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. 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.
The aforementioned 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.
Scale of integration
Small Scale Integration (SSI):
SSI were the first integrated circuits, which contained only a few transistors. They consisted of circuits, containing transistors numbering in the tens.
SSI circuits were vital to early aerospace projects. The Minuteman missile and the Apollo program both needed lightweight digital computers for their inertial guidance systems. the integrated-circuit technology development was led by the Apollo guidance computer, while the Minuteman missile bolstered it into mass-production.
The purchase of almost all of the available integrated circuits from 1960 through 1963, was from these programs, and basically almost provided the demand that funded the production improvements. In turn this got the production costs from $1000 per circuit (in 1960 dollars) to a mere $25 per circuit (in 1963 dollars). They began to become used in consumer products at the turn of the decade, for example in FM inter-carrier sound processing in television receivers.
Medium Scale Integration (MSI):
In this devices which contained hundreds of transistors on each chip. Also, these cost little more to produce than SSI devices, and also allowed more complex systems to be produced, using smaller circuit boards and less assembly work (due to fewer individual components).
Large Scale Integration (LSI):
Large-Scale Integration ” ( LSI ) by the mid 1970s. Chips now were developed with tens of thousands of transistors.
Integrated circuits such as 1K-bit RAMs, calculator chips, and the very first microprocessors had under 4000 transistors and saw a moderate quantity of manufacture in the early part of 1970. True LSI circuits, were approaching 10000 transistors and began to be produced for computer main memories and second-generation microprocessors in around 1974 .
Very Large Scale Integration (VLSI):
Starting in the 1980s and continuing through to this day, was “Very Large-Scale Integration” (VLSI). This starts with hundreds of thousands of transistors in the early 1980s, and continues beyond several billion transistors as of 2007.
No single breakthrough allowed the increase in complexity. Manufacturing moved to cleaner fabs and smaller rules, which allowed them to produce chips with more transistors with adequate yield, (summarized by the International Technology Roadmap for Semiconductors). Design tools also saw much improvement, this was enough to make it practical to finish the designs in reasonable times. Energy efficient CMOS replaced NMOS and PMOS, which avoided a prohibitive increase in power consumption. Many other factors helped also.
By 1986 the first one megabit RAM chips were introduced, these contained more than a million transistors. 2005 saw microprocessor chips passing the billion transistor mark. The trend continues largely unabated, with chips introduced in 2007 containing tens of billions of memory transistors.
Ultra Large Scale Integration (ULSI):
Ultra-Large Scale Integration” was proposed for chips of complexity of more than 1 million transistors.
Wafer-scale integration (WSI):
Wafer-scale integration (WSI) is a system of building extremely large integrated circuits that uses a whole 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 in massively parallel supercomputers. The name is taken from the term Very-Large-Scale Integration, the current state of the art during the development time of WSI.
System-on-a-Chip (SoC or SOC):
It is an integrated circuit where all the components needed for a computer (or other system), are included on a single chip. The design of this device can be costly and extremely complex, and also building disparate components on a single piece of silicon, could compromise the efficiency of some of its’ elements. Nevertheless these drawbacks are offset by low manufacturing and assembly costs, and by a vastly reduced power budget (as the signals among the components are kept on-die, much less power is required).
Three Dimensional Integrated Circuit (3D-IC):
It has two or more layers of active electronic components, these are integrated both horizontally and vertically into a single circuit. Communication between the layers relies on on-die signaling, so the power consumption is lower than that of equivalent separate circuits. Sensible use of short vertical wires can substantially reduce the total wire length, for faster operation and efficiency.
Classification of ICs by Structure:
2.Hybrid or Multichip ICs
In these ICs all circuit components (i.e. active and passive) are fabricated inseparable within a single continuous piece of silicon crystalline material called WAFER. In Monolithic ICs all components are formed simultaneously by a diffusion process. Then a metallization process is used in interconnecting these components to form the desired circuit.
In Hybrid ICs passive components (such as resistors and capacitors) and the interconnection between them are formed on an insulating substrate, the substrate is used as a chassis for the integrated components .Active components such as transistors and diodes, as well as Monolithic ICs are then connected to form a complete circuit. Hybrid ICs are further classified as Thin Film and Thick Film, depending on the method used to form the resistor, capacitor and related interconnections on the substrate.
1.Thin Film: When a suitable material is evaporated on substrate informing resistors, capacitors and interconnections, a Thin Film Hybrid IC is obtained.
2.Thick Film: When the resistors, capacitors andinterconnections are etched on the substrate by silk screening, a Thick Film Hybrid IC is obtained.
Classification of ICs by Function:
Linear ICs: They perform amplification and other essential linear operation on signals.
Non Linear ICs: They require only ON-OFF operation of the transistor, thus the design requirements for these circuits are less stringent than those of linear ICs.
ICs can be classified into ANALOG, DIGITAL and MIXED SIGNAL
Digital integrated circuits:
It 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 Integrated cicuits:
It contains 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.
Mixed integrated cicuits:
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.
Some common terms used in fabricating ICs are:
Bonding: Attaching the die on ceramic substrate and then connecting the leads to the package.
Chip: An extremely small part of silicon wafer on which IC is fabricated.
Circuit Probing: Testing the electrical performance of each IC chip with the help of microscope.
Diffusion: A process that consist of the introduction of impurities into selected regions of a wafer to form junctions.
Encapsulation: putting a cap over the IC and sealing it in an inert atmosphere.
Epitaxy: A process of controlled growth of a crystalline doped layer of silicon on a single crystal substrate.
Mask: A glass plate with desired pattern of diffusion or metallization.
Metallization: A process for providing ohmic contacts and interconnections by evaporating aluminum over the chip.
Photolithography: A process to transfer geometrical pattern from the mask to the surface of the wafer.
Photoresist: A light-sensitive material that hardens when exposed to ultraviolet light.
Wafer: A thin disk of semiconductor in which number of ICs are fabricated simultaneously.
Advantages of ICs over Discrete Components:
Extremely small physical size
Low power consumption
Increased system reliability
Increased operating speed
Increase equipment density
Improved function performance
Advances in integrated circuits
Along with the advanced integrated circuits are that of the ” cores ” or microprocessors, which handle many of today’s appliances from computers and cellular phones to digital microwave ovens. Digital memory chips and ASICs are examples of other groups of integrated circuits which are important to the modern information society. Whilst cost of designing and developing a complex integrated circuit is high, when costs are spread across typically millions of production units, the individual IC cost is reduced. The performance of Integrated circuits is high as the small size allows short traces, which then allows low power logic (for example CMOS), to be used at quick switching speeds.
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Integrated circuits have constantly migrated to smaller feature sizes over time thus, allowing more circuitry to be placed on each chip. The increase in capacity per unit area can be used to decrease cost and increase functionality, this can be seen in Moore’s law where it states that the number of transistors in an integrated circuit doubles every two years in a modern interpretation. Normally as the feature size shrinks, there can be seen improvements in everything. The cost per unit and the power consumption of switching go down, and the speed goes up. Integrated circuits with nanometer-scale devices have a variety of problems, one of which being current leakage, however these problems are not unconquerable and it is likely they will be solved, or improved at least, by the introduction of high-k dielectrics. As the power consumption and speed gains are apparent to the end user, there is competition among manufacturers to use finer geometries. The process/expected progress over the next few years, is described by the International Technology Roadmap for Semiconductors (ITRS).
Popularity of ICs
Â Only a half century after their development was initiated, integrated circuits have become ubiquitous. Computers, cellular phones, and other digital appliances are now inextricable parts of the structure of modern societies. That is, modern computing, communications, manufacturing and transport systems, including the Internet, all depend on the existence of integrated circuit.
Future scope of integrated circuits
The future of integrated electronics is the future of electronics itself. The advantages of integration will bring about a proliferation of electronics, pushing this science into many new areas. Integrated circuits will lead to such wonders as home computers.or at least terminals connected to a central computer .automatic controls for automobiles, and personal portable communications equipment. The electronic wristwatch needs only a display to be feasible today. But the biggest potential lies in the production of large systems. In telephone communications, integrated circuits in digital filters will separate channels on multiplex equipment. Integrated circuits will also switch telephone circuits and perform data processing. Computers will be more powerful, and will be organized in completely different ways. For example, memories built of integrated electronics may be distributed throughout the machine instead of being concentrated in a central unit. In addition, the improved reliability made possible by integrated circuits will allow the construction of larger processing units. Machines similar to those in existence today will be built atlower costs and with faster turn-around.
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