Fabrication of Zener Diode Using IC Techniques

This lecture, authored by Dr. G. S. Virdi, Ex-Chief Scientist, CSIR–Central Electronics Engineering Research Institute, Pilani, presents a comprehensive study on the fabrication of Zener diodes using integrated circuit (IC) fabrication techniques. The lecture covers the fundamental working principles of the Zener diode, including its reverse bias characteristics and the concept of breakdown voltage.

It explains each step of the fabrication process—from wafer preparation, epitaxial growth, oxidation, and photolithography to etching, doping, and metallization. Emphasis is placed on how precise doping and process control result in the formation of high-quality Zener diodes suitable for IC applications.

The lecture is highly beneficial for engineering and science students, and serves as a useful reference for researchers working in semiconductor device fabrication and microelectronics. It will be uploaded on SlideShare for wider academic and professional learning.

1. ZenerDiodeFabrication using IC Techniques
Dr.G.S.Virdi
Ex.Chief Scientist
CSIR -Central Electronics Engineering
Research Institute,Pilani -333031,India
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2. ZenerDiodeFabrication
ZenerDiode:
Zenerdiodeisaformofsemiconductordiode
inwhichatacriticalreversevoltagealargereversecurrentcan
flow.Itworkssameaspnjunctiondiodeinforwardbiasbutin
reversebiasatcertainbreakdownvoltage,largecurrentflow
butuptothatzenervoltageitwillnotallowthecurrentto
flow.Forthatthematerialsshouldbeheavilydoped.Inzener
diodetheconcentrationsofmaterialsarehighsuchthatthe
depletionwidthislessandhashighelectricfieldstrengthresult
inflowingcurrentatlowervoltagesknownasfieldionization.
FabricationProcess:
1.Initiallytakeap-typeSi wafer.Wetakeacross
sectionalviewofSiwafer,looklikeasimpleplanerectangular
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3. 2.EpitaxialLayer:
FormepitaxiallayerontopofP-SIwaferwithhigh
concentration(p+).ForminganewlayeronSi-waferisknownas
"epitaxy",thelayerisepitaxiallayer.
3.Oxidation:
DepositSiO2layerontopofthematerialthrough
layering.SiO2formsatransparentglassslikelayeronthesingle
crystalsubstrate.SiO2isexcellentinsulatingmaterualithsvery
goodmasking
properties
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4. 4.PhotoLithography:
Fordopingselectively,wehavetoremovethemaskby
photolithography.WecovertheentiresurfaceofoxidizedSi
withaphotosensitivematerialcalledaphotoresist.Bringthis
photoresistcoatedsubstrateincontactwithmask(glassor
transparent).ThensubjectittoUVradiation,afterthatitiseasy
toremovethephotoresist.
Afterdevelopment
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5. 5.Etching:
SiO2isremovedindesiredplacethroughetching
processusingsomechemicalreactions.
6.Doping:
Addingspecificamountofelectricallyactiveimpurities
tosilicon.ThroughDopingn+typematerialisdiffusedintothe
p+typematerial.
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6. 7.Photolithography:
AgainbyphotolithographyandetchingremovetheSiO2
onp+typematerial.
Afteretching
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7. 8.Metallization:
DepositAlmetalontopof theSiO2layerformetal
contacts.
ByetchingprocesswehavetoremoveAlontheSiO2layer.
AfterdevelopingtheZenerdiodewithmetalcontactsis
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8. 8
iv characteristics of zener diode
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9. 9
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