Etch-Basic

1ContentsContentsDryEtchOverviewMetalEtchOxideEtchSiliconEtchResistStripDryEtchModuleBasicsDryEtchModuleBasicsTrainingMaterialsforEngineers2DryEtchOverviewDryEtchOverviewDry(plasma)etchinginICFabricationWhatisplasmaWhatisplasmaetchingWhyplasmaetchingisneededWhathappensinplasmaetchingEtchingmechanismGeneraletchrequirement3DryEtchOverviewDryEtchOverviewDry/PlasmaEtchinginICFabricationDry/PlasmaEtchinginICFabricationAtechniqueoftransferringAtechniqueoftransferringphotolithographicphotolithographicpatternstosiliconsubstratepatternstosiliconsubstratee.g.PolysiliconGateFormationResistPatterningPolysiliconDepositionSiliconPolysiliconGoxPlasmaetching4DryEtchOverviewDryEtchOverviewWhatisplasmaWhatisplasma!Gasdischargenegativecharge(electrons)positivecharge(ions)equalno.ofnegativeandpositivechargeneutralspecies----------++++++hhhhGasinletPlasma5DryEtchOverviewDryEtchOverviewWhatisplasmaetchingWhatisplasmaetching!Materials(Si,SiO2,Al,Ti,W,TiN,…)+!Reactivespeciesinplasma(F,Cl,Br,…)+!Ionbombardment(CF2+,BClx+,Ar+,…)⇒Volatilereactionproducts(SiF4,AlCl3,…)+Pumpedaway⇒Etching6DryEtchOverviewDryEtchOverviewWhyplasmaetchingisneededforICfabricationWhyplasmaetchingisneededforICfabrication!Anisotropicetchprofile!Nosurfacetensioneffect!Controllability⇒Smallfeaturesize(3µµµµm)LiquidSisubstrateFilmResistFilmSisubstrateSisubstrateSisubstrateAnisotropicIsotropicSurfacetension7DryEtchOverviewDryEtchOverviewWhathappensinplasmaetchingWhathappensinplasmaetchingNeutralSpecies-diffusion+Positiveions-bombardmentReactionwithsubstrateLowerelectrodeWaferResistSelf-biasNeutralspeciesionsUpperelectrode8DryEtchOverviewDryEtchOverviewEtchingmechanismEtchingmechanismSputteringSubstrateMaskSubstrateMaskVolatileProductSubstrateMaskVolatileProductSubstrateMaskVolatileProductInhibitorChemicalGasificationEnergeticIon-InducedInhibitorIon-Induced9DryEtchOverviewDryEtchOverviewGeneralRequirementsGeneralRequirementsEtchrateUniformitySelectivityAnisotropyProfilecontrolResistremainingSubstratedamagePolymercontrolIondensityElectrontemperatureNeutraldensityionbombardingenergy...RFpowerRFfrequencyGasflowrateGasratioElectrodedistanceElectrodetemperatureMagneticfield.EtchperformancePlasmapropertiesEtchparameters10MetalEtchMetalEtchBackgroundintroductionHardwareintroductionProcessparameterDefects111.1.Metalinsemiconductor:Mainfunction:1.Providepowersupply2.Forinter-connectbetweendifferenttransistorsHDPOxP-welln-wellHDPOxP-SubstrateHDPOxSPACERPolySalicideILDILDILDILDLiningOxIMD-1IMD-1IMD-1IMD-1IMD-2IMD-2IMD-2IMD-2IMD-3IMD-3IMD-3IMD-3IMD-4IMD-4IMD-4IMD-4M-1M-1M-1M-2M-2M-2M-3M-3M-3M-4M-5M-5M-5M-4M-4HDPOxPESiNMetalEtchMetalEtchBackgroundIntroductionBackgroundIntroduction121.2.TypicalMetalFilmStack22/25:M1:AlCuM2-5:AlCu18:M1-6:AlCuMetalEtchMetalEtchBackgroundIntroductionBackgroundIntroduction13WFilmStackI-linePR5kAWTiNARCTi/TiNbarrierlayerSiO2substrateMetalEtchMetalEtchBackgroundIntroductionBackgroundIntroduction140.5~0.25technologyBelow0.25technologySiO2substrateI-linePR4~8KAlCu4~8KAlCuTiNARCTi/TiNbarrierlayerDUVPRTiN+SiON/organicBARCTi/TiNbarrierlayerAlCuFilmStackMetalEtchMetalEtchBackgroundIntroductionBackgroundIntroduction151.3.MetalFilmMaterial(1).AlCuorW:Al-Easytodeposit&etch-Lowresistivity:~2.7micro-ohm-cm-WelladhesiontoSiO2-Lowcost-EasyforwirebondingCuadded-Reduceelectromigration&hillock-Typical0.5%addedtoAlfilmW-BetterresistancetoelectromigrationMetalEtchMetalEtchBackgroundIntroductionBackgroundIntroduction16(2).ARC(anti-reflectivecoating):a.Alreflectsmostoftheincidentlightb.ARCabsorbslighttoreducereflectionc.TiN,organicBARCareoftenusedd.SiONasARCforbelow0.25technology(3).Ti/TiNbarrierlayer:a.Ti:Forreducingcontactresistanceb.TiN:PreventinginterdifusionofSi&Al.c.TiNasgluelayerforWdeposition.*BothARC&barrierlayerTiNhavebenefitforelectromigration.MetalEtchMetalEtchBackgroundIntroductionBackgroundIntroduction171.4Photoresist(PR)issues:(1).Adverseconditionsinmetaletch:-Hightemperatures-HighionbombardmenttoetchARCandbarriermetal,erodePR-At150-200⇒⇒⇒⇒PRreticulation-Above200⇒⇒⇒⇒PRburns-DamagedorhardenedPRdifficulttoremove-WaferbacksideHecoolingisimportant(2).NeedsomePRerosionforpolymergenerationForCl2/BCl3/ArChemistryonlyMetalEtchMetalEtchBackgroundIntroductionBackgroundIntroduction181.5Metaletchchemistry:(1).Cl2:-Al+Cl2AlCl3(volatile)-Evennoplasmapresent,AlcanreactwithCl2-Chemicalisotropicetchbehavior,needpolymerformationonsidewallforanisotropicetch-CanetchTi&TiN,cannotetchAl2O3(2).BCl3:-BreakthroughTIN(ARC)-LowerdownAlE/RbycontrolCl•inplasma-Anisotropicetching-PrimaryoxideetchantbybomardmentMetalEtchMetalEtchBackgroundIntroductionBackgroundIntroduction19(3).Ar:-Ionbombardment-Helptoremoveresidue-Enhanceplasmadissociationdegree(4).N2:-ForbetterPRselectivity&side-wallpassivation-ReduceE/Rmicro-loading(5).CHF3-SidewallpassivationMetalEtchMetalEtchBackgroundIntroductionBackgroundIntroduction202.1Normalprocesssequence:(1).Loadwaferorientor(2).Mainchamber(metaletch)(3).Stripchamber(removePR&residueCl2Temp:250to275deg)(4).Cooldownmodule(wafercooling,preventcassettedamage)