IC Technology First

8/7/2019 IC Technology First

1/15

IC TechnologyIC Technology

First ICFirst IC

An IC (Integrated Circuit) is acomplete electronic circuit inwhich both active and passivecomponents are fabricated onan extremely tiny single chip of

silicon.

IC


2/15

Active Components

Active components are those which haveability to produce gain.

e.g. Transistor

Passive Components

Passive components are those which donot have the ability to produce gain.

e.g. Resistor

Advantages of IC Extremely small physical size

Very small weight

Low cost

Extremely high reliability

Suitability for small signal operation

Low power consumption

Easy replacement

It handles only limited power

it is quite delicate and cannot withstandrough handling and excessive heat

It functions at fairly low voltages

Drawbacks of IC


3/15

Scale of Integration

SSI (Small Scale Integration)

MSI (Medium Scale Integration)

LSI (Large Scale Integration)

VLSI (Very Large Scale Integration)

Scale Integration

(SSI) < 5050


4/15

IC Terminology

Chip

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

IC Terminology

Circuit Probing

To check the proper electrical performance

IC Terminology

Die

Chip

IC Terminology

Diffusion

Controlled introduction of material intocrystal structure to modify its electricalcharacteristics


5/15

IC Terminology

Diffusion Mask

It is a glass plate with the circuit patterndrawn on it.

Encapsulation

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

IC Terminology

Epitaxy

Physical placement of materials on a givensurface.

Etching

Removal of surface material from a chip bychemical means.

Metalization

Providing ohmic contacts andinterconnections by evaporating aluminiumover the chip.

IC Terminology

Photoresist

A photo sensitive emulsion which ishardened when exposed to UV light.

Scribing

Cutting with sharp point

IC Terminology


6/15

Wafer

A thin slice of semiconductor material inwhich 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 Packing12. Encapsulation

How monolithic ICs are made? CzochralskiCzochralski ProcessProcess

TheThe CzochralskiCzochralski process is a method of crystalprocess is a method of crystal

growth used to obtain single crystals ofgrowth 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 JanThe 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 ofwhile investigating the crystallization rates of

metals.metals.


7/15

CzochralskiCzochralski ProcessProcess

A puller rod with seed crystal for growing singleA puller rod with seed crystal for growing single--

crystal silicon by thecrystal silicon by the CzochralskiCzochralski processprocess


HighHigh--purity, semiconductorpurity, semiconductor--grade silicon isgrade silicon ismelted down in a crucible , which is usuallymelted down in a crucible , which is usuallymade of quartz.made of quartz.

DopantDopant impurity atoms such as boron orimpurity atoms such as boron orphosphorus can be added to the moltenphosphorus can be added to the moltenintrinsic silicon in precise amounts in orderintrinsic silicon in precise amounts in orderto dope the silicon, thus changing it into nto dope the silicon, thus changing it into n--type or ptype or p--type extrinsic silicon. Thistype extrinsic silicon. Thisinfluences the electrical conductivity of theinfluences the electrical conductivity of thesilicon.silicon.

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

into the molten silicon.into the molten silicon.

The seed crystal's rod is pulled upwards andThe seed crystal's rod is pulled upwards androtated at the same time.rotated at the same time.

By precisely controlling the temperatureBy precisely controlling the temperaturegradients, rate of pulling and speed ofgradients, rate of pulling and speed ofrotation, it is possible to extract a large,rotation, it is possible to extract a large,singlesingle--crystal, cylindrical ingot from thecrystal, cylindrical ingot from themelt.melt.

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



8/15


IngotIngotMain Steps

Wafer Preparation

6 mils

1 mils = 25 m

Substrate

p-type

Main Steps

Epitaxial Growth

Substrate p-type

n-type 1mils

Main Steps

Epitaxial Growth

Epitaxyrefers to the method of depositing amonocrystalline film on a monocrystallinesubstrate.

The deposited film is denoted as epitaxial film orepitaxial layer.

The term epitaxycomes from a Greek root(epi "above" and taxis "in ordered manner") whichcould be translated to "arrange upon".


9/15

Epitaxial Growth

HomoepitaxyHomoepitaxy is a kind ofis a kind ofepitaxyepitaxyperformedperformedwith only one material.with only one material.

InIn homoepitaxyhomoepitaxy, a crystalline film is grown, a crystalline film is grownon a substrate (or film) of the sameon a substrate (or film) of the samematerial.material.

This technology is applied to growing a moreThis technology is applied to growing a morepurified film than the substrate andpurified film than the substrate andfabricating layers with different dopingfabricating layers with different dopinglevels.levels.

Epitaxial Growth

HeteroepitaxyHeteroepitaxyis a kind ofis a kind ofepitaxyepitaxyperformed with materials that areperformed with materials that aredifferent from each other.different from each other.

InIn heteroepitaxyheteroepitaxy, a crystalline film grows, a crystalline film growson a crystalline substrate (or film) ofon a crystalline substrate (or film) ofanother material.another material.

Epitaxial Growth

This technology is often applied toThis technology is often applied togrowing crystalline films of materialsgrowing crystalline films of materialsof which single crystals cannot beof which single crystals cannot beobtained and to fabricating integratedobtained and to fabricating integratedcrystalline layers of different materials.crystalline layers of different materials.ExamplesExamples GaNGaN on sapphire.on sapphire.

Epitaxial Growth


10/15


11/15

IC Fabrication IC Fabrication

IC Fabrication IC Fabrication


12/15

IC Fabrication Monolithic DiodeMonolithic Diode

Monolithic DiodeMonolithic Diode Monolithic DiodeMonolithic Diode


13/15

Multiple emitterMultiple emitter npnnpn transistortransistor Multiple emitterMultiple emitter npnnpn transistortransistor

Multiple emitterMultiple emitter npnnpn transistortransistor

n-type epitaxial layer

p-type substrate

p+ p+

E4 E3 E2 E1C CB

n+ n+ n+ n+n+ n+

Basic Monolithic Integrated CircuitsBasic Monolithic Integrated Circuits

EpitaxialEpitaxial GrowthGrowthAnAn nn--typetype epitaxialepitaxial layer of 25m thick is grown over alayer of 25m thick is grown over a pp--typetype

substrate which has asubstrate which has a resistivityresistivityof typically 10 of typically 10 --cm,cm, i.e.i.e.

NNaa==1.41.410101515 atoms/ cmatoms/ cm33..

TheThe resistivityresistivityofofepitaxialepitaxial layer generally 0.1 to 0.5 layer generally 0.1 to 0.5 --cm.cm.

After cleaning and polishing, thin layer ( 0.5 m ) of SiOAfter cleaning and polishing, thin layer ( 0.5 m ) of SiO22 is formedis formed

over the entire wafer.over the entire wafer.

p-type substrate


SiO2


14/15


SiOSiO22 is grown by exposing theis grown by exposing the epitaxialepitaxial layer to an oxygenlayer to an oxygen

atmosphere at the temperature of 1000atmosphere at the temperature of 1000oo C.C.

Silicon dioxide has the fundam ental property ofSilicon dioxide has the funda m ental property of

pr even tin g t he d iff us ion of im pu rit ies t hr ough it .pr even tin g t he d iff us ion of im pu rit ies t hr ough it .

p-type substrate


SiO2


Isolation DiffusionIsolation Diffusion

p-type substrate

p+p+p+p+

UV



p-type substrate

p+p+p+p+




15/15





The oxide is removed in four different places on the surface.The oxide is removed in four different places on the surface.

The removal is done by photolithographic etching process.The removal is done by photolithographic etching process.

The remainingThe remaining SiO2 serves as a mask for the diffusionSiO2 serves as a mask for the diffusion

p-type substrate

p+ isolation layer

n+ n+n+n+n+p+p+p+p+

Anode Cathode Base Emitter Collector

IC Technology First

Documents