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IC TechnologyIC Technology

First ICFirst IC

An IC (Integrated Circuit) is a complete electronic circuit in which both active and passive components are fabricated on an extremely tiny single chip of silicon.

IC Active Components

Active components are those which have ability to produce gain.

e.g. Transistor

Passive Components

Passive components are those which do not have the ability to produce gain.

e.g. Resistor

Advantages of ICExtremely small physical size

Very small weight

Low cost

Extremely high reliability

Suitability for small signal operation

Low power consumption

Easy replacement

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It handles only limited power

it is quite delicate and cannot withstand rough handling and excessive heat

It functions at fairly low voltages

Drawbacks of IC Scale of Integration

SSI (Small Scale Integration)

MSI (Medium Scale Integration)

LSI (Large Scale Integration)

VLSI (Very Large Scale Integration)

Scale Integration

(SSI) < 5050 <(MSI) < 5,0005,000 <(LSI) < 10,00010,000 <(VLSI) < 1,000,0001,000,000< Ultra Large Scale Integration (ULSI) < 10,000,00010,000,000 > Giga Scale Integration (GSI) < 100,000,000

Classification of ICs by Structure

Monolithic(active & passive)

Thick Film Thin Film

Film(passive)

Hybrid(active & passive)

Integrated Circuits

IC Terminology

Bonding

Attachment of wire to an IC

IC Terminology

Chip

An extremely small part of a silicon wafer on which IC is fabricated.

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IC TerminologyCircuit Probing

To check the proper electrical performance

IC Terminology

Die

Chip

IC Terminology

Diffusion

Controlled introduction of material into crystal structure to modify its electrical characteristics

IC Terminology

Diffusion Mask

It is a glass plate with the circuit pattern drawn on it.

Encapsulation

Putting a cap over the IC and sealing it in an inert atmosphere.

IC Terminology

Epitaxy

Physical placement of materials on a given surface.

Etching

Removal of surface material from a chip by chemical means.

Metalization

Providing ohmic contacts and interconnections by evaporating aluminiumover the chip.

IC Terminology

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Photoresist

A photo sensitive emulsion which is hardened when exposed to UV light.

Scribing

Cutting with sharp point

IC Terminology

Wafer

A thin slice of semiconductor material in which circuits are fabricated.

IC Terminology

How monolithic ICs are made?

1. Wafer Preparation

2. Epitaxial Growth

3. Oxidation

4. Photolithographic Process

5. Isolation Diffusion

6.Base and Emitter Diffusion

7. Pre-ohmic Etch

8. Metalization

9. Circuit Probing

10. Scribing into Chips

11. Mounting and Packing

12. Encapsulation

How monolithic ICs are made?

EpitaxialEpitaxial Growth Growth

CzochralskiCzochralski ProcessProcess

CzochralskiCzochralski ProcessProcess

The The CzochralskiCzochralski process is a method of crystal process is a method of crystal growth used to obtain single crystals of growth used to obtain single crystals of semiconductors. semiconductors.

e.ge.g. silicon, germanium and gallium arsenide.. silicon, germanium and gallium arsenide.

The process is named after Polish scientist Jan The process is named after Polish scientist Jan CzochralskiCzochralski, who discovered the method in 1916 , who discovered the method in 1916 while investigating the crystallization rates of while investigating the crystallization rates of metals.metals.

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CzochralskiCzochralski ProcessProcess

A puller rod with seed crystal for growing singleA puller rod with seed crystal for growing single--crystal silicon by the crystal silicon by the CzochralskiCzochralski processprocess

CzochralskiCzochralski ProcessProcess

HighHigh--purity, semiconductorpurity, semiconductor--grade silicon is grade silicon is melted down in a crucible , which is usually melted down in a crucible , which is usually made of quartz. made of quartz.

DopantDopant impurity atoms such as boron or impurity atoms such as boron or phosphorus can be added to the molten phosphorus can be added to the molten intrinsic silicon in precise amounts in order intrinsic silicon in precise amounts in order to dope the silicon, thus changing it into nto dope the silicon, thus changing it into n--type or ptype or p--type extrinsic silicon. This type extrinsic silicon. This influences the electrical conductivity of the influences the electrical conductivity of the silicon. silicon.

CzochralskiCzochralski ProcessProcessA seed crystal, mounted on a rod, is dipped A seed crystal, mounted on a rod, is dipped

into the molten silicon. into the molten silicon. The seed crystal's rod is pulled upwards and The seed crystal's rod is pulled upwards and

rotated at the same time. rotated at the same time. By precisely controlling the temperature By precisely controlling the temperature

gradients, rate of pulling and speed of gradients, rate of pulling and speed of rotation, it is possible to extract a large, rotation, it is possible to extract a large, singlesingle--crystal, cylindrical ingot from the crystal, cylindrical ingot from the melt. melt.

This process is normally performed in an This process is normally performed in an inert atmosphere, such as argon, and in an inert atmosphere, such as argon, and in an inert chamber, such as quartz.inert chamber, such as quartz.

CzochralskiCzochralski ProcessProcess

CzochralskiCzochralski ProcessProcessIngotIngot Main Steps

Wafer Preparation

6 mils

1 mils = 25 µm

Substratep-type

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Main Steps

Epitaxial Growth

Substrate p-type

n-type 1mils

Main StepsEpitaxial Growth

Epitaxy refers to the method of depositing a monocrystalline film on a monocrystallinesubstrate.

The deposited film is denoted as epitaxial film or epitaxial layer.

The term “epitaxy” comes from a Greek root (epi "above" and taxis "in ordered manner") which could be translated to "arrange upon".

Epitaxial GrowthHomoepitaxyHomoepitaxy is a kind of is a kind of epitaxyepitaxy performed performed

with only one material. with only one material.

In In homoepitaxyhomoepitaxy, a crystalline film is grown , a crystalline film is grown on a substrate (or film) of the same on a substrate (or film) of the same material. material.

This technology is applied to growing a more This technology is applied to growing a more purified film than the substrate and purified film than the substrate and fabricating layers with different doping fabricating layers with different doping levels.levels.

Epitaxial Growth

HeteroepitaxyHeteroepitaxy is a kind of is a kind of epitaxyepitaxyperformed with materials that are performed with materials that are different from each other. different from each other.

In In heteroepitaxyheteroepitaxy, a crystalline film grows , a crystalline film grows on a crystalline substrate (or film) of on a crystalline substrate (or film) of another material. another material.

Epitaxial Growth

This technology is often applied to This technology is often applied to growing crystalline films of materials growing crystalline films of materials of which single crystals cannot be of which single crystals cannot be obtained and to fabricating integrated obtained and to fabricating integrated crystalline layers of different materials. crystalline layers of different materials. Examples Examples GaNGaN on sapphire.on sapphire.

Epitaxial Growth

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Epitaxial Growth

SiCl4 + 2H2 Si + 4HCl1200o C

Epitaxial Growth

Main Steps

Oxidation

[ Dry Oxidation][ Dry Oxidation]SiSi + O+ O22= SiO= SiO22

[ Wet Oxidation][ Wet Oxidation]SiSi + 2H+ 2H22O = SiOO = SiO22 + 2H+ 2H22

Main Steps

Oxidation

p-type substrate

n-type epitaxial layerSiO2