CMP化学机械研磨

Chapter12ChemicalMechanicalPolishingHongXiao,Ph.D.hxiao89@hotmail.comwww2.austin.cc.tx.us/HongXiao/Book.htmwww2.austin.cc.tx.us/HongXiao/Book.htmObjectives ListapplicationsofCMP DescribebasicstructureofaCMPsystem DescribeslurriesforoxideandmetalCMP DescribeoxideCMPprocess. Describemetalpolishingprocess. Explainthepost-CMPcleanwww2.austin.cc.tx.us/HongXiao/Book.htmOverview Multilayermetalinterconnection Planarizationofdielectriclayers Depthoffocusrequireflatsurfacetoachievehighresolution Theroughdielectricsurfacecanalsocauseproblemsinmetallizationwww2.austin.cc.tx.us/HongXiao/Book.htmICFabWaferProcessFlowwww2.austin.cc.tx.us/HongXiao/Book.htmTungstenCMP Tungstenhasbeenusedtoformmetalplugs CVDtungstenfillscontact/viaholesandcoversthewholewafer. Needtoremovethebulktungstenfilmfromthesurface Fluorinebasedplasmaetchbackprocesses TungstenCMPreplacedetchbackwww2.austin.cc.tx.us/HongXiao/Book.htmP-EpiP-WaferMetal3Al•CuAlloyIMD3USGMetal4Al•CuUSGSiliconNitrideAl•CuAlloyN-WellP-WellBPSGn+n+p+p+STIUSGWAl•CuAlloyUSGM1M2Al•CuUSGWIMD1IMD2TiSi2TiTiNARCWTi/TiNTi/TiNSidewallSpacer,USGPMDBarrierNitrideIMD3Passivation1Passivation2PMDCMPPSG,WCMPUSG,WCMPUSG,WCMPUSGWCMPUSGCMOSICwww2.austin.cc.tx.us/HongXiao/Book.htmDefinitionofPlanarization Planarizationisaprocessthatremovesthesurfacetopologies,smoothesandflattensthesurface Thedegreeofplanarizationindicatestheflatnessandthesmoothnessofthesurfacewww2.austin.cc.tx.us/HongXiao/Book.htmDefinitionofPlanarizationCompletelyConformalFilm,NoPlanarizationConformalandSmooth,NoPlanarizationwww2.austin.cc.tx.us/HongXiao/Book.htmDefinitionofPlanarizationPartialPlanarizationGlobalPlanarizationwww2.austin.cc.tx.us/HongXiao/Book.htmDegreesofPlanaritywww2.austin.cc.tx.us/HongXiao/Book.htmPlanarityR(m)SurfaceSmoothing0.1to2.0>30(LocalPlanarization2.0to10030(to0.5(GlobalPlanarization>100<0.5(DefinitionofPlanarityRqwww2.austin.cc.tx.us/HongXiao/Book.htmPlanarization Smoothingandlocalplanarizationcanbeachievedbythermalfloworetchback Globalplanarizationisrequiredforthefeaturesizesmallerthan0.35mm,whichcanonlybeachievedbyCMPwww2.austin.cc.tx.us/HongXiao/Book.htmOtherPlanarizationMethods Thermalflow Sputteringetchback Photoresistetchback, Spin-onglass(SOG)etchbackwww2.austin.cc.tx.us/HongXiao/Book.htmThermalFlow Dielectricplanarization Pre-metaldielectric Hightemperature,~1000C PSGorBPSG,becomesoftandstarttoflowduetothesurfacetension Smoothandlocalplanarizationwww2.austin.cc.tx.us/HongXiao/Book.htmAsDepositedBPSGP-typesubstratep+p+N-wellP-typesubstrateSiO2n+n+p+p+www2.austin.cc.tx.us/HongXiao/Book.htmAfterThermalFlowBPSGP-typesubstratep+p+N-wellP-typesubstrateSiO2n+n+p+p+www2.austin.cc.tx.us/HongXiao/Book.htmEtchBack ReflowtemperatureistoohighforIMD canmeltaluminum OtherplanarizationmethodisneededforIMD Sputteringetchbackandreactiveetchbackwww2.austin.cc.tx.us/HongXiao/Book.htmEtchBack Argonsputteringetchbackchipoffdielectricatcornerofthegapandtapertheopenings SubsequentCVDprocesseasilyfillsthegapwithareasonableplanarizedsurface ReactiveionetchbackprocesswithCF4/O2chemistryfurtherplanarizesthesurfacewww2.austin.cc.tx.us/HongXiao/Book.htmCVDUSGUSGAl·Cu·SiBPSGP-typesubstratep+p+N-wellP-typesubstraten+n+p+p+SiO2www2.austin.cc.tx.us/HongXiao/Book.htmSputteringEtchBackofUSGUSGAl·Cu·SiBPSGP-typesubstratep+p+N-wellP-typesubstraten+n+p+p+SiO2www2.austin.cc.tx.us/HongXiao/Book.htmCVDUSGUSGAl·Cu·SiBPSGP-typesubstratep+p+N-wellP-typesubstraten+n+p+p+SiO2www2.austin.cc.tx.us/HongXiao/Book.htmReactiveEtchBackofUSGUSGAl·Cu·SiBPSGP-typesubstratep+p+N-wellP-typesubstraten+n+p+p+SiO2www2.austin.cc.tx.us/HongXiao/Book.htmPhotoresistEtchback PRspin-coatscanbaking Planarizedsolidthinfilmonwafersurface PlasmaetchprocesswithCF4/O2chemistry OxideetchedbyFandPRbyO AdjustingCF4/O2flowratioallows1:1ofoxidetoPRselectivity. Oxidecouldbeplanarizedafteretchbackwww2.austin.cc.tx.us/HongXiao/Book.htmAfterOxideDepositedOxideMetalMetalwww2.austin.cc.tx.us/HongXiao/Book.htmPhotoresistCoatingandBakingOxidePhotoresistMetalMetalwww2.austin.cc.tx.us/HongXiao/Book.htmPhotoresistEtchbackOxideMetalMetalwww2.austin.cc.tx.us/HongXiao/Book.htmPhotoresistEtchbackOxideMetalMetalwww2.austin.cc.tx.us/HongXiao/Book.htmPhotoresistEtchbackOxideMetalMetalwww2.austin.cc.tx.us/HongXiao/Book.htmPhotoresistEtchback WhenFetchoxide,Owillbereleased HigherPRetchrateduetoextraoxygen PRetchbackcan’tplanarizeverywell AfterthePRetchback,dielectricfilmsurfaceisflatterthanitisjustdeposited. Insomecases,morethanonePRetchbackisneededtoachieverequiredflatnesswww2.austin.cc.tx.us/HongXiao/Book.htmSOGEtchback SOGreplacesPR Advantage:someSOGcanstayonthewafersurfacetofillthenarrowgaps PECVDUSGlinerandcaplayer USG/SOG/USGgapfillandsurfaceplanarization Sometimes,twoSOGcoat,cureandetchbackprocessesareusedwww2.austin.cc.tx.us/HongXiao/Book.htmSOGEtchbackwww2.austin.cc.tx.us/HongXiao/Book.htmNecessityofCMP PhotolithographyresolutionR=K1l/NA Toimproveresolution,NAorl DOF=K2l/2(NA)2,bothapproachestoimproveresolutionreduceDOF DOFisabout2,083Åfor0.25mmand1,500Åfor0.18mmresolution. HereweassumedK1=K2,l=248nm(DUV),andNA=0.6www2.austin.cc.tx.us/HongXiao/Book.htmNecessityofCMP 0.25mmpatternrequireroughness<2000Å OnlyCMPcanachievethisplanarization Whenfeaturesize>0.35mm,othermethodscanbeusedwww2.austin.cc.tx.us/HongXiao/Book.htmAdvantagesofCMP Planarizedsurfaceallowshigherresolutionofphotolithographyprocess TheplanarizedsurfaceeliminatessidewallthinningbecauseofpoorPVDstepcoveragewww2.austin.cc.tx.us/HongXiao/Book.htmMetalLineThinningDuetotheDielectricStepMetal1Metal2IMD1PMDSidewallThinningwww2.austin.cc.tx.us/HongXiao/Book.htmPlanarizedDielectricSurface,noMetalLineThinningEffectMetal1IMD1PMDMetal2www2.austin.cc.tx.us/HongXiao/Book.htmAdvantagesofCMP Eliminatetherequirementofexcessiveexposureanddevelopmenttoclearthethickerphotoresistregionsduetothedielectricsteps Thisimprovestheresolutionofviaholeandmetallinepatteringprocesses Uniformthinfilmdeposition Reducerequiredoveretchtime Reducechanceofundercutorsubstratelosswww2.austin.cc.tx.us/HongXiao/Book.htmOverExposureandOverDevelopmentPRMetal2Metal2IMD1PRPRNeedsmoreexposureanddevelopmentPossibleCDlossduetomoreexposureanddevelopmentwww2.austin.cc.tx.us/HongXiao/Book.htmRoughSurface,LongOverEtchMetal2Metal2IMD1PRPRNeedalongoveretchtoremovewww2.austin.cc.tx.us/HongXiao/Book.htmFlatSurface,ShortOverEtchMetal2Metal2PRPRVerylitteroveretchisrequiredIMD1www2.austin.cc.tx.us/HongXiao/Book.htmAdvantagesofCMP CMPreducedefectdensity,improveyield Reducingtheprocessproblemsinthinfilmdeposition,photolithography,andetch. CMPalsowidensICchipdesignparameters CMPcanintroducedefectsofitsown Needappropriatepost-CMPcleaningwww2.austin.cc.tx.us/HongXiao/Book.htmApplicationsofCMP STIformation Dielectriclayerplanarization PMDandIMD Tungstenplugformation Deeptrenchcapacitorwww2.austin.cc.tx.us/HongXiao/Book.htmApplicationsofCMPwww2.austin.cc.tx.us/HongXiao/Book.htmDeepTrenchCapacitorHeavilydopedSiSiliconSubstratePadOxidewww2.austin.cc.tx.us/HongXiao/Book.htmDeepTrenchCapacitorHeavilydopedSiSiliconSubstrateNitridePadOxidewww2.austin.cc.tx.us/HongXiao/Book.htmDeepTrenchCapacitorHeavilydopedSiSiliconSubstrateNitridePadOxidewww2.austin.cc.tx.us/HongXiao/Book.htmDeepTrenchCapacitorHeavilydopedSiSiliconSubstrateNitridePadOxidewww2.austin.cc.tx.us/HongXiao/Book.htmDeepTrenchCapacitorHeavilydopedSiSiliconSubstrateNitridePadOxidewww2.austin.cc.tx.us/HongXiao/Book.htmDeepTrenchCapacitorHeavilydopedSiSiliconSubstrateNitridePadOxidewww2.austin.cc.tx.us/HongXiao/Book.htmDeepTrenchCapacitorDielectricLayerHeavilydopedSiSiliconSubstrateNitridePadOxidewww2.austin.cc.tx.us/HongXiao/Book.htmDeepTrenchCapacitorDielectricLayerHeavilydopedSiSiliconSubstrateNitridePadOxidewww2.austin.cc.tx.us/HongXiao/Book.htmDeepTrenchCapacitorDielectricLayerHeavilydopedSiSiliconSubstratePolysiliconNitridePadOxidewww2.austin.cc.tx.us/HongXiao/Book.htmDeepTrenchCapacitorDielectricLayerHeavilydopedSiSiliconSubstratePolysiliconNitridePadOxidewww2.austin.cc.tx.us/HongXiao/Book.htmDeepTrenchCapacitorDielectricLayerHeavilydopedSiSiliconSubstratePolysiliconNitridePadOxidewww2.austin.cc.tx.us/HongXiao/Book.htmDeepTrenchCapacitorDielectricLayerHeavilydopedSiSiliconSubstratePolysiliconPadOxidewww2.austin.cc.tx.us/HongXiao/Book.htmDeepTrenchCapacitorDielectricLayerHeavilydopedSiSiliconSubstratePolysiliconwww2.austin.cc.tx.us/HongXiao/Book.htmApplicationsofCMP Copperinterconnection. Copperisverydifficulttodryetch, Dualdamascene:processofchoice Tungstenplugisadamasceneprocesswww2.austin.cc.tx.us/HongXiao/Book.htmApplicationsofCMP Itusestwodielectricetchprocesses, oneviaetchandonetrenchetch Metallayersaredepositionintoviaholesandtrenches. AmetalCMPprocessremovescopperandtantalumbarrierlayer Leavecopperlinesandplugsimbeddedinsidethedielectriclayerwww2.austin.cc.tx.us/HongXiao/Book.htmPECVDNitrideP-EpiP-WaferN-WellP-Welln+STIp+p+USGWPSGNitriden+www2.austin.cc.tx.us/HongXiao/Book.htmPECVDUSGP-EpiP-WaferN-WellP-Welln+STIp+p+USGWPSGUSGNitriden+www2.austin.cc.tx.us/HongXiao/Book.htmPECVDEtchStopNitrideP-EpiP-WaferN-WellP-Welln+STIp+p+USGWPSGUSGNitriden+www2.austin.cc.tx.us/HongXiao/Book.htmPECVDUSGP-EpiP-WaferN-WellP-Welln+STIp+p+USGWPSGUSGn+USGwww2.austin.cc.tx.us/HongXiao/Book.htmPhotoresistCoatingP-EpiP-WaferN-WellP-Welln+STIp+p+USGWPSGUSGn+USGPhotoresistwww2.austin.cc.tx.us/HongXiao/Book.htmVia1Maskwww2.austin.cc.tx.us/HongXiao/Book.htmVia1MaskExposureandDevelopmentP-EpiP-WaferN-WellP-Welln+STIp+p+USGWPSGUSGn+USGPhotoresistwww2.austin.cc.tx.us/HongXiao/Book.htmEtchUSG,StoponNitrideP-EpiP-WaferN-WellP-Welln+STIp+p+USGWPSGUSGn+PhotoresistUSGwww2.austin.cc.tx.us/HongXiao/Book.htmStripPhotoresistP-EpiP-WaferN-WellP-Welln+STIp+p+USGWPSGUSGn+USGwww2.austin.cc.tx.us/HongXiao/Book.htmPhotoresistCoatingP-EpiP-WaferN-WellP-Welln+STIp+p+USGWPSGUSGn+USGPhotoresistwww2.austin.cc.tx.us/HongXiao/Book.htmMetal1Maskwww2.austin.cc.tx.us/HongXiao/Book.htmMetal1MaskExposureandDevelopmentP-EpiP-WaferN-WellP-Welln+STIp+p+USGWPSGUSGn+USGPhotoresistwww2.austin.cc.tx.us/HongXiao/Book.htmEtchUSGandNitrideP-EpiP-WaferN-WellP-Welln+STIp+p+USGWPSGn+PhotoresistUSGUSGwww2.austin.cc.tx.us/HongXiao/Book.htmStripPhotoresistP-EpiP-WaferN-WellP-Welln+STIp+p+USGWPSGn+USGUSGwww2.austin.cc.tx.us/HongXiao/Book.htmDepositTantalumBarrierLayerP-EpiP-WaferN-WellP-Welln+STIp+p+USGWPSGn+USGUSGwww2.austin.cc.tx.us/HongXiao/Book.htmDepositCopperP-EpiP-WaferN-WellP-Welln+STIp+p+USGWPSGn+USGUSGCopperwww2.austin.cc.tx.us/HongXiao/Book.htmCMPCopperandTantalumP-EpiP-WaferN-WellP-Welln+STIp+p+USGWPSGn+USGUSGCuM1www2.austin.cc.tx.us/HongXiao/Book.htmPECVDSealNitrideP-EpiP-WaferN-WellP-Welln+STIp+p+USGWPSGn+USGUSGCuM1www2.austin.cc.tx.us/HongXiao/Book.htmCMPHardware Polishingpad Wafercarrier Slurrydispenserwww2.austin.cc.tx.us/HongXiao/Book.htmChemicalMechanicalPolishingSlurryPolishingPadPressureWaferHolderWaferMembranePlatenSlurryDispenserRetainingRingwww2.austin.cc.tx.us/HongXiao/Book.htmLinearPolishingSystemSlurryPressureWaferCarrierWaferMembraneSlurryDispenserRetainingRingPadConditionerBeltandPolishingPadSupportFluidBearingwww2.austin.cc.tx.us/HongXiao/Book.htmOrbitalPolishingDownForceSlurryWaferCarrierFilmwcOrbitalMotion,wpPolishPadwww2.austin.cc.tx.us/HongXiao/Book.htmPolishingPad Porous,flexiblepolymermaterial cast,slicedpolyurethaneorurethanecoatedpolyesterfelt PaddirectlyaffectsqualityofCMPprocess Padmaterials:durable,reproducible,compressibleatprocesstemperature Processrequirement:hightopographyselectivitytoachievesurfaceplanarizationwww2.austin.cc.tx.us/HongXiao/Book.htmPolishingPadHardness Harderpolishingpad:higherremovalrateandbetterwithindie(WID)uniformity Softerpad:betterwithinwafer(WIW)uniformity. Hardpadseasiertocausescratches. Thehardnessiscontrolledbypadchemicalcompositionsorbycellularstructure.www2.austin.cc.tx.us/HongXiao/Book.htmPolishingPad Cellsabsorbpolishingslurry Fillerimprovemechanicalproperties Polishingpadsurfaceroughnessdeterminestheconformalityrange. Smootherpadhaspoorertopographicalselectivitylessplanarizationeffect. Rougherpadhaslongerconformalityrangeandbetterplanarizationpolishingresultwww2.austin.cc.tx.us/HongXiao/Book.htmHardRoughPadPolishingPadFilmWaferPadMovementwww2.austin.cc.tx.us/HongXiao/Book.htmSoftSmoothPadPolishingPadFilmWaferPadMovementwww2.austin.cc.tx.us/HongXiao/Book.htmPadConditioning Padbecomessmootherduetothepolishing Needtorecreateroughpadsurface In-situpadconditionerforeachpad Theconditionerresurfacesthepad Removestheusedslurry Suppliesthesurfacewithfreshslurrywww2.austin.cc.tx.us/HongXiao/Book.htmPolishingPadandPadConditionerWaferCarrierSlurryDispenserPadConditionerPolishingPadwww2.austin.cc.tx.us/HongXiao/Book.htmPolishingHead Polishingheadisalsocalledwafercarrier Itconsistsofapolishingheadbody Retainingring Carriermembrane Downforcedrivingsystemwww2.austin.cc.tx.us/HongXiao/Book.htmPolishingHeadPolishingHeadBodyRetainingRingCarrierMembranewww2.austin.cc.tx.us/HongXiao/Book.htmSchematicofPolishingHeadVacuumChuckDownforcePressureRestrainingRingPositioningWaferRestrainingRingRestrainingRingMembraneCarrierChamberwww2.austin.cc.tx.us/HongXiao/Book.htmPadConditioner Sweepsacrossthepadtoincreasesurfaceroughnessrequiredbyplanarizationandremovestheusedslurry Conditionerisastainlesssteelplatecoatedwithnickel-plateddiamondgrits DiabondCMPconditioner:stainlesssteelplatecoatedwithCVDdiamondfilmplateddiamondgridswww2.austin.cc.tx.us/HongXiao/Book.htmSurfaceofCMPConditionersStainlessSteelPlateNickelFilmDiamondGritsConventionalStainlessSteelPlateDiamondFilmDiamondGrits(~20mm)DiabondSiliconSubstratewww2.austin.cc.tx.us/HongXiao/Book.htmCMPSlurries Chemicalsintheslurryreactwithsurfacematerials,formchemicalcompoundsthatcanberemovedbyabrasiveparticles Particulateinslurrymechanicallyabradethewafersurfaceandremovematerials AdditivesinCMPslurrieshelptoachievedesiredpolishingresultswww2.austin.cc.tx.us/HongXiao/Book.htmCMPSlurries CMPslurriesworkjustliketoothpaste Chemicalskillgems,removetartar,andformprotectionlayerontheteeth Particlesabradeawayunwantedcoatingfromtoothsurfaceduringtoothbrushingwww2.austin.cc.tx.us/HongXiao/Book.htmCMPSlurries Water-basedchemicalswithabrasiveparticlesandchemicaladditives Differentpolishingprocessesrequiredifferentslurries Slurrycanimpactremovalrate,selectivity,planarityanduniformity Slurriesalwaysareengineeredandformulatedforaspecificapplication.www2.austin.cc.tx.us/HongXiao/Book.htmCMPSlurries Oxideslurry:alkalinesolutionwithsilica Metalslurry:acidicsolutionwithalumina AdditivescontrolthepHvalueofslurries oxide,pHat10to12 metal,pHat6to2www2.austin.cc.tx.us/HongXiao/Book.htmpHValuespH02468101214MoreAcidicMoreBasic7Neutral13591113www2.austin.cc.tx.us/HongXiao/Book.htmSlurryDelivery Slurrycomponentsarestoredseparately DIwaterwithparticulate additivesforpHcontrol oxidantsformetaloxidation Flowtoamixertomixatrequiredratiowww2.austin.cc.tx.us/HongXiao/Book.htmSlurryFlowDI+SuspensionspHAdjusterOxidantLFCLFCLFCMixerCMPToolLFC:liquidflowcontrollerwww2.austin.cc.tx.us/HongXiao/Book.htmOxideSlurry Basedonexperienceofopticalindustry,whichpolishsilicateglasstomakelensesandmirrorsforalongtime Oxideslurryisacolloidalsuspensionoffinefumedsilica(SiO2)particlesinwater KOHisusedtoadjustthepHat10to12 NH4OHcanalsobeusedwww2.austin.cc.tx.us/HongXiao/Book.htmOxideSlurry Abrasives:fumedsilicaparticles Normallycontain~10%solids Shelflifetimeofupto1yearwithpropertemperaturecontrolwww2.austin.cc.tx.us/HongXiao/Book.htmFumedSilica FumedsilicaparticlesareformedinavaporphasehydrolysisofSiCl4inahydrogen-oxygenflame2H2+O22H2OSiCl4+2H2OSiO2+4HCl OverallreactionSiCl4+2H2+O2SiO2+4HClwww2.austin.cc.tx.us/HongXiao/Book.htmFumedSilicaParticleFormationH2>1800°C<1710°CAggregatesAgglomeratesO2SiCl4CollectionSystemCoolingwww2.austin.cc.tx.us/HongXiao/Book.htmFumedSilicaParticlesCourtesyofFujimiCorporationwww2.austin.cc.tx.us/HongXiao/Book.htmMetalPolishingSlurry MetalCMPprocessissimilartothemetalwetetchprocess Oxidantreactswithmetaltoformoxide Metaloxideisremoved Repeatmetaloxidationandoxideremovalwww2.austin.cc.tx.us/HongXiao/Book.htmMetalPolishingSlurry ThemetalCMPslurriesusuallyarepH-adjustedsuspensionsofalumina(Al2O3) TheslurrypHcontrolsthetwocompetingmetalremovalmechanisms metalcorrosivewetetching metaloxidationpassivationwww2.austin.cc.tx.us/HongXiao/Book.htmMetalPolishingSlurry Differentmetaloxideshavedifferentsolubility Ifoxideissoluble,wetetchwilldominate Notfavored:isotropicwithnotopographicselectivity Ifoxideisinsoluble,itblocksfurtheroxidation Particlesmechanicallyabradeoxidelayer Repeatingmetaloxidationandoxideabrasion favorable:highsurfacetopographicselectivity ThepHvaluecontrolsoxidationprocesswww2.austin.cc.tx.us/HongXiao/Book.htmTungstenSlurry Pourbaixdiagram WhenpH<2,tungstenisinpassivationregime TungstencanformpassivationoxideWO3withpHlowerthan4inthepresenceofanoxidant Oxidants:potassiumferricyanid(K3Fe(CN)6),ferricnitrade(Fe(NO3)3),andH2O2 ForahigherpH,thesolubleW12O4110-,WO42,andW12O396-ionscanbeformed,causewetetchwww2.austin.cc.tx.us/HongXiao/Book.htmPourbaixDiagramforTungstenpH0-112Potential(Eh)VoltsStableWWO2WO3WO42-W12O4110-W12O396-Corrosive02468101214-2www2.austin.cc.tx.us/HongXiao/Book.htmTungstenSlurry AdjustingslurrypHallowslowwetetchratesandchemical-mechanicalpolishremoval TungstenslurriesnormallyarequiteacidicwithpHlevelfrom4to2. Tungstenslurrieshavelowersolidcontentsandmuchshortershelflifetime. TungstenslurriesrequiremechanicalagitationpriortoandduringdeliverytotheCMPtoolswww2.austin.cc.tx.us/HongXiao/Book.htmAluminumSlurry Water-basedacidicsolutions H2O2asoxidant, Aluminaasabrasives. Limitedshelflifetime H2O2moleculeisunstable AluminumCMPisnotpopularlyused Hardtocompetewithcoppermetallizationwww2.austin.cc.tx.us/HongXiao/Book.htmCopperSlurry Acidicsolutions Oxidants:hydrogenperoxide(H2O2),ethanol(HOC2H5)withnitricacid(HNO4),ammoniumhydroxide(NH4OH)withpotassiumferri-andferro-cyanide,ornitricacidwithbenzotriazole Aluminaasabrasiveswww2.austin.cc.tx.us/HongXiao/Book.htmPourbaixDiagramforCopperpH024681012140-1-212Potential(Eh)VoltsPassivationCorrosiveCorrosiveCu+CuImmunityCuOCu2OCu2+CuO22-Passivationregimewithstablealuminawww2.austin.cc.tx.us/HongXiao/Book.htmCopperSlurry Needcolloidallystableslurrytoachieveconsistentpolishingprocessresults AcolloidallystablealuminasuspensioncanbeachievedatpHjustbelow7. Onlyasmallwindowforcopperslurriestoachievebothelectrochemicalpassivationandcolloidallystablesuspensionofaqueousaluminaparticleswww2.austin.cc.tx.us/HongXiao/Book.htmCMPBasics Removalrate Uniformity Selectivity Defectswww2.austin.cc.tx.us/HongXiao/Book.htmRemovalRate MechanicalremovalrateRwasfoundbyPreston ThePrestonequationcanbeexpressedasR=Kppv pisthepolishingpressure KpisthePrestoncoefficient Dvisrelativevelocityofwaferandpadwww2.austin.cc.tx.us/HongXiao/Book.htmRemovalRate Prestonequationworksverywellforthebulkfilmpolishingprocesses Theprotrudingportionsonaroughsurfacehavehigherpolishingpressure Removalrateofprotrudingpartsishigher Thishelpstoremovesurfacetopographyandplanarizethesurfacewww2.austin.cc.tx.us/HongXiao/Book.htmProtrudingPartswithHigherPressurePolishingPadFilmWaferHighPressure,FastRemovalNoPressure,NoRemovalwww2.austin.cc.tx.us/HongXiao/Book.htmRemovalRate ThicknessdifferencebeforeandafterCMPdividedbyCMPtime Multiplemeasurementforuniformity Testwafer,blanketfilm Dailytoolqualificationwww2.austin.cc.tx.us/HongXiao/Book.htmUniformity Usually49-point,3sstandarddeviationasthedefinitionoftheuniformityfortheCMPprocessqualifications ChangesofthefilmthicknessbeforeandafterCMPprocessismonitored Fortheproductionwafers,uniformityafterCMPprocessismonitored Normallyuse9or13pointsmeasurementwww2.austin.cc.tx.us/HongXiao/Book.htmUniformity BothWIWandWTWuniformitycanbeaffectedbythepolishpadcondition,downforcepressuredistribution,relativespeed,restrainingringpositioning,andtheshapeofthewafers. Byusingharderpadandlowerpressureagoodglobaluniformitycanbeachieved Lowerpressure,lowerremovalrate,affectthroughputwww2.austin.cc.tx.us/HongXiao/Book.htmSelectivity Ratioofremovalratesofdiffe