Introduction to Integrated Circuit Technology IC Knowledge

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Introduction to Integrated Circuit Technology,1 0 Introduction. At IC Knowledge LLC we have found a wide diversity in our clients and web site visitors. with respect to their understanding of Integrated Circuit IC technology Some of the people we. interact with have a strong understanding of IC technology but there is also a substantial group. that purchases or uses the technology without a strong understanding For the later group we. though it would be useful to produce a basic introduction to IC technology and that is the objec. tive of this publication, We have written this publication assuming no more technical background than a high school. education and any technical terms will be defined when they are introduced We have attempted. to provide a good high level overview of the technology in this document if you have questions. about the content or would like to provide us with feedback please e mail us at info icknowl. 2 0 Basic electronic concepts, Electronic circuits regulate and control the flow of electric. current Electric current is the flow of electrons the tiny sub Basic Definitions. atomic particles that surround the nucleus of atoms Electrons Current the flow of. carry a fixed negative electric charge and the movement of elec electrons carrying. trons carries charge from one location to another the flow of electric charge. electrons is referred to as electric current Electric current is Voltage the force. driven by a difference in potential from one location to another driving the flow of. measured in volts Electric current flows easily through materials current. that are conductors and is blocked by materials that are insula Resistance a mate. tors The amount of resistance that a material presents to the flow rial s resistance to. of electric current is logically called resistance Conductors have the flow of electric. low resistance to the flow of current and insulators have current. extremely high resistance essentially infinite until the voltage is Conductor a mate. so high that the material breaks down For a given voltage the rial that readily sup. higher the resistance the less current that will flow and the lower ports the flow of. the resistance the higher the current that will flow Conversely electric current. for a given resistance the higher the voltage the more current that Insulator a mate. will flow and the lower the voltage the less current that will flow rial that blocks the. flow of electric cur,3 0 Electronic circuit elements rent. Electronic circuits are made up of a number of elements used. to control current flow There are a wide variety of different circuit elements but for the purpose. of this discussion the circuit elements will be restricted to the four most commonly used in ICs. these are resistors capacitors diodes and transistors Resistors provide a fixed amount of resis. tance to current flow Capacitors store electric charge until discharged somewhat similar to a bat. tery Diodes allow current to flow in one direction but not in the opposite direction a one way. valve Transistors provides two major modes of action one a switch turning current flow on and. off or two act as an amplifier whereby an input current produces a larger output current. Copyright 2001 2012 IC Knowledge LLC all rights reserved 2. Introduction to Integrated Circuit Technology, An Integrated Circuit or IC is nothing more than a number.
of these components connected together as a circuit all formed on IC Circuit Elements. the same substrate Resistors resists,current flow,4 0 What is a Semiconductor Capacitors stores. A semiconductor is a material that may act as a conductor or Diodes allows cur. as an insulator depending on the conditions Diodes and transis rent to flow in only. tors are made with semiconductor material and resistors and one direction. capacitors may be made on or in semiconductor materials as well Transistor. As the scientific community began to understand semiconductor switches and or. materials the transistor and later the IC were invented see His amplifies current. tory of the IC at www icknowledge com for more information. Resistors and capacitors as individual components are commonly. made without the use of semiconductor materials but the ability to make them with semiconductor. material made it possible to integrate them with diodes and transistors Semiconductors may be. made more conductive by adding other impurity elements to the semiconductor material and the. ability to do this selectively i e add impurities to one part of a semiconductor material and not to. other parts is what enables IC fabrication to take place Areas of semiconductor material that are. highly pure and therefore have little or no impurities act as insulators This is the key to IC fabri. cation and will be discussed further in the sections that follow. 5 0 Integrated Circuit Manufacturing Overview, At the highest level the manufacture of ICs may be broken up into 5 major steps see figure. 1 Starting substrate 2 Wafer fabrication 3 Wafer sort test. silicon wafer fabricate IC s test each IC,purchased on the wafer mark bad IC s. 5 Mark class final test 4 Packaging,mark and final assemble IC s. test packaged product into packages 14003,Figure 1 IC manufacturing.
Copyright 2001 2012 IC Knowledge LLC all rights reserved 3. Introduction to Integrated Circuit Technology,The five major steps are. 1 Starting substrate the starting substrate is purchased by virtually all major IC producers. Starting substrates will be discussed further in section 6 0. 2 Wafer fabrication the process of fabricating a numbers of ICs on the surface of the wafer. simultaneously Wafer fabrication will be discussed further in section 8 0. 3 Wafer sort test each IC referred to as a die on the wafer surface is tested and the bad die are. marked with an ink dot or in an electronic map The bad die are discarded after the wafer is. sawn up for packaging to save the cost of packaging bad die Wafer test will be discussed fur. ther in section 10 0, 4 Packaging the wafer is sawn up into individual die and the good die are assembled into pro. tective packages Packaging will be discussed further in section 11 0. 5 Mark and class final test in order to insure that the die were not damaged during packaging. the packaged product is tested and marked with the product type Final test will be discussed. further in section 12 0,6 0 Silicon Wafers, Far and away the most common material for IC fabrication is silicon there are other materi. als in use but only for small niche applications Silicon is an abundant material in the earth s. crust and relatively easy to obtain and refine Silicon is a semiconductor although silicon has. become the dominant IC material not so much because it is a great semiconductor material but. rather because it is relatively easy to work with, The silicon used for IC fabrication has been highly purified grown into nearly perfect crys. tals and sliced up into discs called wafers less than a millimeter mm thick and anywhere from. 100mm 4 to 300mm 12 in diameter smaller sizes were used early in the development of the. industry but are now rarely used in production and 450mm wafers are currently in development. Silicon wafers are highly polished appearing mirror like extremely flat and extremely clean. and particle free at the start of fabrication,100mm 4 125mm 5 and 150mm 6 wafers typ.
ically have a flat section ground onto one or more edges to. mark how the crystal planes are oriented in the wafer and. allow consistent alignment of various layers built up on the. wafer see figure 2a 200mm 8 and 300mm 12 wafers, use a small notch in place of a flat because a flat takes away. an unacceptable amount of wafer area on the larger wafers a Wafer with flat b Wafer with. see figure 2b 150mm notch 200mm, Silicon wafers were at one time internally manufac Figure 2 Silicon wafer orienta. tured by the IC companies who then fabricated circuits on tion indications. them but now virtually all IC manufacturers purchase the. wafers from a third party, There are three major types of silicon wafers currently in use for IC fabrication. Raw wafers silicon wafers without any additional processing For state of the art ICs raw. wafers are mainly used for memory such as DRAM and Flash. Copyright 2001 2012 IC Knowledge LLC all rights reserved 4. Introduction to Integrated Circuit Technology, Epitaxial wafers silicon wafers with a single crystal silicon. layer deposited on them The deposited layer typically has Wafer Types. different properties than the underlying raw wafer Epitaxial Raw basic wafer. layers allow the properties of the layer in which the devices used to make ICs. are formed to be more tailored than in a raw wafer and are Epitaxial Epi a. widely used for the latest state of the art Logic ICs Epitaxial raw wafer with a. wafer costs are 1 4 to 2 5 times the cost of a raw wafer single crystal film. Silicon on Insulator SOI wafers silicon wafers upon which deposited on it. an insulating layer is formed with a thin single crystal silicon Silicon On Insula. layer on top of the insulating layer SOI wafers reduce the tor SOI a thin. amount of power drawn by an IC when the circuit is switching single crystal silicon. at high speed SOI wafers costs are 4 to 15 times the cost of a film on an insulating. raw wafer SOI is primarily used in low power and some high film on a handle. performance applications We expect the use of SOI to wafer. increase and even become mainstream as linewidths continue. Figure 3 illustrates the basic,wafer manufacturing process.
The process steps are Pull Rod,Seed Crystal,Pull crystal ingot a small seed a Pull. of single crystal silicon is crystal,dipped into a crucible of molten Silicon Ingot. silicon The crucible and seed Molten,Single Crystal. are rotated in opposite direc Polysilicon d Saw up. tions and the seed is slowly Coil,b Grind c Saw off ingot into. ingot to ingot wafers,withdrawn from the crucible diameter ends damage.
figure 3a 75 m,Ingot grind the silicon crystal,ingot is ground to create a con e Grind round. edges onto,sistent diameter for the whole f Lap wafers. ingot figure 3b g Damage,removal etch,for flatness. damage 12 m,Saw off ingot ends the two damage 2 m,ends of the silicon ingot will. not be usable and are sawn off, using a diamond saw figure h Mirror polish i Final clean.
wafers damage free, Saw up the ingot into wafers Figure 3 Silicon wafer manufacturing process. the Ingot is sawn up into wafers, each approximately 1 2mm to 3 4mm in thickness 100mm to 300mm wafers figure 3d. Edge grind wafers the edges of the wafers are ground to round off the sharp edges Edge. grinding minimizes chipping of the wafer edges during subsequent processing figure 3e. Lap wafers a process called lapping is used to flatten out the wafers and ensures the two. wafer faces are parallel figure 3f, Damage removal etch a special wet etch is used to etch off the surface damage left from lap. ping figure 3g, Copyright 2001 2012 IC Knowledge LLC all rights reserved 5. Introduction to Integrated Circuit Technology, Polish the polish step removes the final residual damage layer on the wafers and creates a.
mirror polish surface figure 3h, Final clean the final clean step removes any contaminants left on the wafer surface from the. previous steps figure 3i, The resulting wafer is a highly pure nearly perfect single crystal with crystal planes pre. cisely oriented to the wafer surface,7 0 How small is small. Before delving into wafer fabrication the 100 meters. fabrication of incredibly tiny IC elements it is,useful to review the size scale of the circuit. Meter scale, elements being discussed The units of mea Average male 1 78.
meters tall,sure utilized in this publication are defined in. Average female 1 63,table 1 1 meter,meters tall,Table 1 Units of size. 100 millimeters,Unit Symbol Relationship,Millimeter scale. 10 millimeters US Penny 19 05,millimeters in diameter. Millimeter mm One thousand millime and 1 55 millimeters. ters equals one meter 1 millimeter,Micrometer m One million microme.
also called a ters equals one meter 100 micrometers Human hair 30 to 200. micron one thousand microme,Micrometer scale,micrometers in diameter. ters equals one millime,10 micrometers,ter Bacteria 0 7 to 30. micrometers long,Nanometer nm One billion nanometers. equals one meter one 1 micrometer,thousand nanometers. equals one micrometer 100 nanometers,Picometer pm One trillion picometers.
Nanometer scale,equals one meter and Viruses 3 to 50. 10 nanometers nanometers long,one thousand picome,ters equals one nano. meter 1 nanometer,Covalent radius of a, Once the units are defined the size of 100 picometers silicon atom 118. picometers,some common objects may be put in perspec. tive see figure 4 Figure 4 Size scale,The average height of people is measured.
in meters at the millimeter scale is the diameter and thickness of a penny and at the micrometer. scale is the thickness of a human hair and size of bacteria viruses are nanometer scale in size and. finally atoms are picometers in size, The smallest processes currently in production are approximately 20nm processes From fig. ure 4 20nm may be put into perspective relative to some common objects 20nm is on. with respect to their understanding of Integrated Circuit IC technology Some of the people we interact with have a strong understanding of IC technology but there is also a substantial group that purchases or uses the technology without a strong understanding For the later group we though it would be useful to produce a basic introduction to IC technology and that is the objec tive of

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