半导体生产过程

EE4345-SemiconductorElectronicsDesignProjectSiliconManufacturingGroupMembersYoungSoonSongNghiaNguyenKeiWongEyadFanousHannaKimStevenHsuHISTORY19thCentury-Solid-StateRectifiers1907-ApplicationofCrystalDetectorinRadioSets1947-BJTConstructedbyBardeenandBrattain1959–IntegratedCircuitConstructedbyKilbySemiconductorManufacturingProcessSemiconductorManufacturingProcessFundamentalProcessingSteps1.SiliconManufacturinga)Czochralskimethod.b)WaferManufacturingc)Crystalstructure2.Photolithographya)Photoresistsb)PhotomaskandReticlesc)Patterning3.OxideGrowth&Removala)OxideGrowth&Depositionb)OxideRemovalc)Othereffectsd)LocalOxidation4.Diffusion&IonImplantationa)Diffusionb)Othereffectsc)IonImplantationSemiconductorManufacturingProcess(cont)SiliconManufacturingCrystalGrowthandWaferManufacturingFABRICATINGSILICONQuartz,orSilica,ConsistsofSiliconDioxideSandContainsManyTinyGrainsofQuartzSiliconCanbeArtificiallyProducedbyCombiningSilicaandCarboninElectricFurniceGivesPolycrystallineSilicon(multitudeofcrystals)PracticalIntegratedCircuitsCanOnlybeFabricatedfromSingle-CrystalMaterialCRYSTALGROWTHCzochralskiProcessisaTechniqueinMakingSingle-CrystalSiliconASolidSeedCrystalisRotatedandSlowlyExtractedfromaPoolofMoltenSiRequiresCarefulControltoGiveCrystalsDesiredPurityandDimensionsCYLINDEROFMONOCRYSTALLINETheSiliconCylinderisKnownasanIngotTypicalIngotisAbout1or2MetersinLengthCanbeSlicedintoHundredsofSmallerCircularPiecesCalledWafersEachWaferYieldsHundredsorThousandsofIntegratedCircuitsWAFERMANUFACTURINGTheSiliconCrystalisSlicedbyUsingaDiamond-TippedSawintoThinWafersSortedbyThicknessDamagedWafersRemovedDuringLappingEtchWafersinChemicaltoRemoveanyRemainingCrystalDamagePolishingSmoothesUnevenSurfaceLeftbySawingProcessTHECRYSTALSTRUCTUREOFSILICONAUnitCellHas18SiliconsAtomsWeakBondingAlongCleavagePlanesWaferSplitsinto4or6Wedge-ShapedFragmentsMillerIndicesisUsedtoAssigntoEachPossiblePlanePassingThroughtheCrystalLatticeSiliconManufacturingPhotolithographyPhotolithographyPhotolithographyisatechniquethatisusedtodefinetheshapeofmicro-machinedstructuresonawafer.PhotolithographyPhotoresistThefirststepinthephotolithographyprocessistodevelopamask,whichwillbetypicallybeachromiumpatternonaglassplate.Next,thewaferisthencoatedwithapolymerwhichissensitivetoultravioletlightcalledaphotoresist.Afterward,thephotoresististhendevelopedwhichtransfersthepatternonthemasktothephotoresistlayer.PhotolithographyPhotoresistTherearetwobasictypesofPhotoresistsPositiveandNegative.Positiveresists.Positiveresistsdecomposesultravioletlight.TheresistisexposedwithUVlightwherevertheunderlyingmaterialistoberemoved.Intheseresists,exposuretotheUVlightchangesthechemicalstructureoftheresistsothatitbecomesmoresolubleinthedeveloper.Theexposedresististhenwashedawaybythedevelopersolution,leavingwindowsofthebareunderlyingmaterial.Themask,therefore,containsanexactcopyofthepatternwhichistoremainonthewafer.PhotolithographyPhotoresistNegativeresistsExposuretotheUVlightcausesthenegativeresisttobecomepolymerized,andmoredifficulttodissolve.Therefore,thenegativeresistremainsonthesurfacewhereveritisexposed,andthedevelopersolutionremovesonlytheunexposedportions.Masksusedfornegativephotoresists,therefore,containtheinverse(orphotographicnegative)ofthepatterntobetransferred.PhotolithographyModelFigure1ashowsathinfilmofsomematerial(eg,silicondioxide)onasubstrateofsomeothermaterial(eg,asiliconwafer).Photoresistlayer(Figure1b)Ultravioletlightisthenshonethroughthemaskontothephotoresist(figure1c).PhotolithographyModel(cont)Thephotoresististhendevelopedwhichtransfersthepatternonthemasktothephotoresistlayer(figure1d).Achemical(orsomeothermethod)isthenusedtoremovetheoxidewhereitisexposedthroughtheopeningsintheresist(figure1e).Finallytheresistisremovedleavingthepatternedoxide(figure1f).PhotolithographyPhotomasksandReticlesPhotomaskThisisasquareglassplatewithapatternedemulsionofmetalfilmononeside.Themaskisalignedwiththewafer,sothatthepatterncanbetransferredontothewafersurface.Eachmaskafterthefirstonemustbealignedtothepreviouspattern.PhotolithographyPhotomasksandReticlesWhenaimageonthephotomaskisprojectedseveraltimesidebysideontothewafer,thisisknownassteppingandthephotomaskiscalledareticle.Ancommonreticleisthe5XThepatternsonthe5Xreticlearereduced5timeswhenprojectedontothewafer.Thismeansthediesonthephotomaskare5timeslargerthantheyareonthefinalproduct.Thereareotherkindsofreductionreticles(2X,4X,and10X),butthe5Xisthemostcommonlyused.Reductionreticlesareusedonavarietyofsteppers,themostcommonbeingASM,Canon,Nikon,andGCA.PhotolithographyPhotomasksandReticlesExamplesof5XReticles:PhotolithographyPhotomasksandReticlesOncethemaskhasbeenaccuratelyalignedwiththepatternonthewafer'ssurface,thephotoresistisexposedthroughthepatternonthemaskwithahighintensityultravioletlight.Therearethreeprimaryexposuremethods:contact,proximity,andprojection.PhotolithographyPatterningThelaststageofPhotolithographyisaprocesscalledashing.Thisprocesshastheexposedwaferssprayedwithamixtureoforganicsolventsthatdissolvespor