Post on 09-Apr-2018
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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
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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
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Scale of Integration
SSI (Small Scale Integration)
MSI (Medium Scale Integration)
LSI (Large Scale Integration)
VLSI (Very Large Scale Integration)
Scale Integration
(SSI) < 5050
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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
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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
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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.
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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 thecrystal silicon by the CzochralskiCzochralski processprocess
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.
CzochralskiCzochralski ProcessProcess
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CzochralskiCzochralski ProcessProcess
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".
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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
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IC Fabrication IC Fabrication
IC Fabrication IC Fabrication
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IC Fabrication Monolithic DiodeMonolithic Diode
Monolithic DiodeMonolithic Diode Monolithic DiodeMonolithic Diode
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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
n-type epitaxial layer
SiO2
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Basic Monolithic Integrated CircuitsBasic Monolithic Integrated Circuits
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
n-type epitaxial layer
SiO2
Basic Monolithic Integrated CircuitsBasic Monolithic Integrated Circuits
Isolation DiffusionIsolation Diffusion
p-type substrate
p+p+p+p+
UV
Basic Monolithic Integrated CircuitsBasic Monolithic Integrated Circuits
Isolation DiffusionIsolation Diffusion
p-type substrate
p+p+p+p+
Basic Monolithic Integrated CircuitsBasic Monolithic Integrated Circuits
Isolation DiffusionIsolation Diffusion
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Basic Monolithic Integrated CircuitsBasic Monolithic Integrated Circuits
Isolation DiffusionIsolation Diffusion
Basic Monolithic Integrated CircuitsBasic Monolithic Integrated Circuits
Isolation DiffusionIsolation Diffusion
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