Integrated circuit

History

Jack Kilby (1923 - 2005) is the inventor of the integrated circuit. In 1958, this American, then employed by Texas Instruments, created the very first integrated circuit, thus providing the foundations of the modern Computer material. For the little story Jack Kilby, which had just joined the company, made this discovery whereas the majority of his/her colleagues benefitted from holidays organized by Texas Instruments. At the time, Kilby had quite simply connected between them various transistors by cabling them to the hand. It will take thereafter only a few months to pass from the prototype stage of to the mass production of silicon chips containing several transistors. This discovery was worth in Kilby a Nobel Prize of Physique in 2000, whereas this last always sat at the directory of Texas Instruments and held more than 60 Brevet S with its name.

Analogical integrated circuit

The simplest components can be simple Transistor S encapsulated the ones beside the others without connection between them, until assemblies joining together all the functions necessary for the operation of an apparatus of which it is the only component.

The operational amplifier are representatives of average complexity of this big family where one finds also components reserved for high electronics Fréquence and of Télécommunication.

An analogical example of circuit: the amplifier COp LM741 and a long string of cousins.

Numerical integrated circuit

The numerical integrated circuits simplest are logical doors (and, or, not), most complex are the Microprocesseur S and densest are the memories. One finds many integrated circuits dedicated to specific applications ( ASIC for Application Specific Integrated Circuit ), in particular for the treatment of the signal (image processing, video compression…) one speaks then about DSP (for DIGITAL Signal Processor ). An important family of integrated circuits is that of the components of programmable logic (FPGA, CPLD). These components are brought to replace the simple logical doors because of their great level of integretion.

Composition

The case

The integrated circuits are generally appeared as case S full rectangular, black, equipped on one or more sides even on a face, legs (also called pins or pines) making it possible to establish electric connections with the outside of the case. These components are brazed, (welded, unsuitable term) on a Printed circuit, or plugged in, at ends of disassembling, in supports themselves brazed on a printed circuit.

On the case are painted: the logo of the manufacturer, a reference makes it possible to identify the component, a code corresponding to alternatives or revisions and the date of manufacture (4 coded digits AASS: year and week). Progress of integration is such as the integrated circuits can become very small. Their size depends hardly than on the capacity of the case to dissipate the heat produced by Joule effect and, very often of the number, the size of the pins of exit of the circuit as well as theirs spacing.

Various types of cases make it possible to adapt the integrated circuit into its environment of destination.

the oldest format has as a name for Dual Inline Package (DIP or DIL) which results summarily in “case with two lines”.
the miniaturization helping, the circuits known as of surface made their appearance: the format SO

Many other types exist:

Die

The die is the elementary part, of rectangular form, reproduced with identical using a matrix on a silicon wafer in the course of manufacture.

The Die of an integrated circuit includes/understands in miniaturized forms mainly of the Transistor S, Diode S, resistances, condensing S, more rarely of the Inductance S because they are able to be miniaturized with more difficulty.

Scale of integration

The scale of integration defines the number of doors per case:

IF ( small scale integration ) small: lower than 12
MSI ( medium ) average: 12 to 99
LSI ( broad ) large: 100 to 9999
VLSI ( very broad ) very large: 10.000 to 99.999
ULSI ( ultra broad ) ultra large: 100.000 and more

These distinctions little by little lost of their utility with the exponential growth of the number of doors. Today several hundreds of million transistors (several tens of million doors) represent a normal figure (for a microprocessor or a graphic Integrated circuit top-of-the-range). In order to arrive to such levels of integrations, a flood of complex design is used.

Technique of the most current manufacture

The manufacture of an integrated circuit is a complex process whose tendency is to be become complicated more and more.

the basic reason is the Transistor, and they are then the metal interconnections between the transistors which fulfill the particular function of the circuit.
the Aluminum is often employed to this end, but a more powerful technology allows the use of the Cuivre.
One uses sometimes polycrystalline silicon, also conducting, in particular for the grid of the transistor.

Raw material

The basic raw material usually used to manufacture the integrated circuits is the Silicium.

Nevertheless, other materials are sometimes employed, like the Germanium or the Gallium arsenide.

Silicon is a Semi-conducteur in its form mono Cristal line. This Matériau must be pure to 99,99%.

One very slowly manufactures initially a cylindrical bar of silicon by crystallizing it. This bar is then cut out to be used in the form of wafers from 100 to 800 µm thickness and having up to 300 mms in diameter, called wafer (wafer, in English). A wafer will support many integrated circuits.

Photolithogravure

Stages of manufacture

The number of stages of the manufacture of the integrated circuits has grown considerably for 20 years. It can reach several tens for certain specialized productions. However, the same series of stages is about always found:

Preparation of the layer: one exposes the Wafer to pure Dioxygène after heating to manufacture an oxide coating (insulator) on the surface, then the wafer is covered with a photosensitive varnish.
Transfer: one transfers the drawing from the circuit to be reproduced on photosensitive surface using a mask, as for painting with the stencil key set, by exposing it to the Ultraviolet S, (or with the X-rays, for the finest engravings). The varnish not subjected to the east radiations dissolves thanks to a specific solvent.
Engraving: the silicon oxide is thus protected by varnish at the places exposed to the ultra-violets. A corrosive agent will dig the oxide coating at the not protected places.
Doping: one dissolves then varnish exposed with another solvent, and of the metal ions, called doping , is introduced into exposed silicon where the oxide was dug, in order to make it conducting.
following Layer: the operation is renewed to create the successive layers of the integrated circuit or the microprocessor (up to 20).
One determines the quality of engraving according to the smallest reason which it is possible to engrave, in fact the width of the grid of transistor MOS.

In 2004, the finest engravings in production are of 0,13 µm (or 130 Nm) and 90 Nm .
In 2006, the finest engravings in production are of 60 Nm and 30 Nm .

Final stages

One deposits a metal film at the places where the circuit will have to be in contact with the pins of exit.
the integrated circuits are tested directly on the wafer. The defective chips are marked. It is about EWS
the wafer is finally cut out with the diamond or via a laser process of cutting to obtain die .
the chips thus obtained are inserted in an individual case of protection and are connected to the pins which will enable them to communicate with outside.
Of the severe and individual tests of validation is then undertaken to qualify the microprocessors, in frequency and temperature.

Specialized technologies

Certain techniques are also used for integrated circuits of a little specialized type.

Silicon on insulator

Technology ( silicon one insulator - ONESELF) consists in electrically introducing an insulating layer under in-depth transistors of silicon. That reduces the losses of electron S in the circuit, sources of static consumption of energy. Silicon “at side” of the transistors is not fixed any more at a given potential, which introduces interesting performances (increase speed for complex doors CMOS).

Silicon on sapphire

In certain cases, the single-crystal silicon substrate is purely and simply abandoned. The intrinsic advantage to use silicon (the arrangement of the silicon atoms on the Substrat is naturally more regular) can then be compensated for specialized applications. Thus the silicon on sapphire (crystalline sapphire substrate) is used in the applications where the integrated circuit will be exploited in an environment space or subjected to intense radiations which would make the silicon substrates unusable.

Gallium arsenide

One also carries out semiconductors containing Gallium arsenide. Even if this material had anteriority on silicon, it had almost disappeared from industry. Today the intrinsic advantages of this material in terms commutation rate, like its performances higher than that of silicon in the field of the Opto-electronic , give again to him a new youth in the field of the high frequencies and one sees reappearing an industrial production on the basis of this technology.

Future developments

The industry of the integrated circuits is one of those which evolve/move most quickly of the history of technologies. It explores new technologies continuously. Among those which seem to have a promising future it is necessary to count:

diamond substrates, which one waits much in terms of cooling

See too

Simple: Integrated circuit Zh-yue: 集成電路

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