Integrated circuit

Integrated circuit

nd consume little power (compared to their discrete counterparts) as a result of the small size and
close proximity of the components. As of 2006, typical chip areas range from a few square
millimeters to around 350 mm2, with up to 1 million transistors per mm2.

[edit] Terminology
Integrated circuit originally referred to a miniaturized electronic circuit consisting of
semiconductor devices, as well as passive components bonded to a substrate or circuit board.[1]
This configuration is now commonly referred to as a hybrid integrated circuit. Integrated circuit
has since come to refer to the single-piece circuit construction originally known as a monolithic
integrated circuit.[2]

[edit] Invention
Early developments of the integrated circuit go back to 1949, when the German engineer Werner
Jacobi (Siemens AG) [1] filed a patent for an integrated-circuit-like semiconductor amplifying
device [3] showing five transistors on a common substrate arranged in a 2-stage amplifier
arrangement. Jacobi disclosed small and cheap hearing aids as typical industrial applications of
his patent. 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).
Dummer presented the idea to the public at the Symposium on Progress in Quality Electronic
Components in Washington, D.C. on May 7, 1952.[4] He gave many symposia publicly to
propagate his ideas, and 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. 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).[5] However, as the project was gaining momentum, Kilby
came up with a new, revolutionary design: the IC.

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.[6]

Jack Kilby's original integrated circuit

Newly employed by Texas Instruments, Kilby recorded his initial ideas concerning the integrated
circuit in July 1958, successfully demonstrating the first working integrated example on
September 12, 1958.[7] 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.‖[8]Kilby won the 2000 Nobel Prize in Physics for his part of the
invention of the integrated circuit.[9]Kilby's work was named an IEEE Milestone in 2009.[10]

Noyce also came up with his own idea of an integrated circuit half a year later than Kilby. His
chip solved many practical problems that Kilby's had not. Produced at Fairchild Semiconductor,
it was made of silicon, whereas Kilby's chip was made of germanium.

Fairchild Semiconductor was also home of the first silicon gate IC technology with self-aligned
gates, which stands at the basis of all modern CMOS computer chips. The technology was
developed by Italian physicist Federico Faggin in 1968, who later joined Intel in order to develop
the very first Central Processing Unit (CPU) on one chip (Intel 4004), for which he received the
National Medal of Technology and Innovation in 2010.

[edit] Generations
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, and manufacturing yields were
low by today's standards. As the degree of integration was small, the design was done easily.
Over time, millions, and today billions,[11] of transistors could be placed on one chip, and to
make a good design became a task to be planned thoroughly. This gave rise to new design
methods.

[edit] 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[citation needed], from there came the terms for SSI, MSI,
VLSI, and ULSI.

SSI circuits were crucial to early aerospace projects, and aerospace projects helped inspire
development of the technology. 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,[12] 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.[13] 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 10,000 transistors, began to be produced around 1974, for
computer main memories and second-generation microprocessors.

[edit] VLSI

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 design rules and cleaner fabrication facilities, 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.[14] The trend continues largely unabated, with chips introduced in
2007 containing tens of billions of memory transistors.[15]

[edit] 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 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. 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.

[edit] Advances in integrated circuits

The die from an Intel 8742, an 8-bit microcontroller that includes a CPU running at 12 MHz, 128
bytes of RAM, 2048 bytes of EPROM, and I/O in the same chip

Among the most advanced integrated circuits are the microprocessors or "cores", which control
everything from computers and cellular phones to digital microwave ovens. Digital memory
chips and ASICs are examples of other families of integrated circuits that are 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. 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.

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. 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. 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).

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.[16] As one of the few materials well established in CMOS technology, titanium nitride
(TiN) turned out as exceptionally stable and well suited for electrode applications in medical
implants.[17][18]

[edit] Classification

A CMOS4000 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, and mixing. 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.

RESISTOR
A linear resistor is a linear, passivetwo-terminalelectrical component that implements electrical
resistance as a circuit element. The current through a resistor is in direct proportion to the voltage
across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's terminals
to the intensity of current through the circuit is called resistance. This relation is represented by
Ohm's law:

Resistors are common elements of electrical networks and electronic circuits and are ubiquitous
in most electronic equipment. Practical resistors can be made of various compounds and films, as
well as resistance wire (wire made of a high-resistivity alloy, such as nickel-chrome). Resistors
are also implemented within integrated circuits, particularly analog devices, and can also be
integrated into hybrid and printed circuits.

The electrical functionality of a resistor is specified by its resistance: common commercial
resistors are manufactured over a range of more than nine orders of magnitude. When specifying
that resistance in an electronic design, the required precision of the resistance may require
attention to the manufacturing tolerance of the chosen resistor, according to its specific
application. The temperature coefficient of the resistance may also be of concern in some
precision applications. Practical resistors are also specified as having a maximum power rating
which must exceed the anticipated power dissipation of that resistor in a particular circuit: this is
mainly of concern in power electronics applications. Resistors with higher power ratings are
physically larger and may require heat sinks. In a high-voltage circuit, attention must sometimes
be paid to the rated maximum working voltage of the resistor.

Practical resistors have a series inductance and a small parallel capacitance; these specifications
can be important in high-frequency applications. In a low-noise amplifier or pre-amp, the noise
characteristics of a resistor may be an issue. The unwanted inductance, excess noise, and
temperature coefficient are mainly dependent on the technology used in manufacturing the
resistor. They are not normally specified individually for a particular family of resistors
manufactured using a particular technology.[1] A family of discrete resistors is also characterized
according to its form factor, that is, the size of the device and the position of its leads (or
terminals) which is relevant in the practical manufacturing of circuits using them.

Integrated circuit

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