WET工艺介绍

WETProcessIntroduction2PurposeofWetCleaningProcessThroughtoaseriesofprocessestomakethewafersfreefromparticles,organiccontaminations,metalcontamination,surfacemicroroughnessandnativeoxideusingsomekindsofchemicalsincludingDIW.3PurposeofWetCleaningProcessForEtchingprocess•Oxideremove.•Nitrideremove.•Photoresist&polymerremove.ForCleaningprocess•Freeofparticles.•Freeofmetalion.•Freeoforganic.•Freeofmicro-roughness.•Freeofnativeoxide.4WetCleaning(Pre-treatment)WetCleaning(Post-treatment)ResistRemovalDiffusionCVDPVDLithographyEtchingDopingWaferInWaferOutICProcessing5WetProcess1.FEOLpost-ashclean35%-typicalSPM.-trendistointegrateresiststripingandcleaning.2.Pre-diffusionclean30%-RCAclean-trendistousedilutechemistriestoreducecost,improveequipmentreliabilityandprocessperformance.3.BEOLpost-etchclean20%-issueswithtechnical,cost,environment-trendistousesinglewaferdryclean4.Others(PostCMPandspecialcleaning)15%-SC1basedcleaning6•ChemicalName•H2O(DI)De-Ionizedwater•H2SO4SulfuricAcid•H2O2HydrogenPeroxide•H2OWater•HFHydrofluoricAcid•NH4OHAmmoniumHydroxide•HClHydrochloricAcid•IPAIsopropylalcohol•O3Ozone•H3PO4PhosphoricAcidChemicalsInvolved7Wetbench89PurposeofPre-cleanistoremovethelastunwantedoxidelayerandpreparesurfacefreeofmetalliccontaminantsandgoodPCfornextoxidation.Pre-diffusionclean-RCAcleanH2O:H2O2:NH4OH(50:2:1)30oCH2ORinseRoomTempH2ORinseH2O:H2O2:HCl(50:1:1)30oCH2ORinseRoomTempDryerH2O:HF(100:1)23oC10SiO2(s)+6HF(l)H2SiF6(l)+2H2O(l)•Theetchrate(orreactionrateofHFwithoxide)canbeslowedbyaddingmorewaterandlowerstheconcentrationofHF.•HFwilletchBPSGOxideNitSiH2O:HF100:1(50:1,49%)Function:RemoveOxide(SiO2)Mechanism:ReactswithOxideandformasolvablebyproduct.OxideEtchHFH2O:H2O2:NH4OH(50:2:1)30oCH2ORinseRoomTempH2ORinseH2O:H2O2:HCl(50:1:1)30oCH2ORinseRoomTempDryerH2O:HF(100:1)23oC11EtchingoffnativeoxideleavinghydrophobicSisurface,repelsH2O,thatispronetoH2OmarkAsamethodtopassivatesurface,H2O2/SC1/SC2lastisused.AftercleaningHFonSi,theSiwaferhasH2SiF6=itischargedupwithSiF62-ions=thishashighaffinitytoattractdefects,duetostrongpolarity.12WhatisH2Omark?ItissomeH2OstainwhichoxidisestheSisurface.ItcanalsobeaconcentrationofH2Ocontaminants.H2OattractedareaeasytocreateH2OmarkoxoxSiwafer13Whatistheimpactofwatermark?Watermarkcancauseproblemswithadhesionoffilms,contactresistance,non-uniformitybetweenconductinglayers,blocketch,gateoxidedefects.Howtopreventit?•Treatthewafersurfacewitheg.H2O2,SC1,SC2(someoxidationeffects)toensurehydrophilicsurfacethroughout.•Ensuredryersperformance1.VaporJetdryer2.LowpressureDryer3.SpinDryer4.MicroMistDryer14DIwaterisDe-ionizedwater.TapwaterNa+Cl-Na+K+K+Cl-F-F-WaterRinse:DIWaterDe-ionizedwaterH2O:H2O2:NH4OH(50:2:1)30oCH2ORinseRoomTempH2ORinseH2O:H2O2:HCl(50:1:1)30oCH2ORinseRoomTempDryerH2O:HF(100:1)23oC15DIWtankisforrinsingwaferascleanaspossiblebeforegoingintothenextchemicaltanktopreventcross-contaminationorbeforeleavingthehood.DIWcanoverfloworquickdumprinse(QDR).OverflowisverystableflowofDIWandgivesgoodPCcontrol.Itmakesuseofdiffusionanddilution.QDR,ontheotherhandmakesuseofextradragforcewhenDIWdump&itisfastatremovingacidtrace,butsincethereismoreagitationinthetank,itmayresultinhigherPC.ControloftheDIWtankandsurroundingcleanlinessisimportant.DIWtankoverflowsatalltimeswithby-passflowtopreventbacteria.BacteriawillresultinPC&metalliccontamination.DIWTank16DIWcanbehotorcold-dependsonpreviousandnexttanks.HotChemicalwillbefollowedbyHotDIW/ColdDIW;thisistopreventthermalshock.Forhighviscositychemical,HDIWrinsewillimprovesolubilityofthechemical,thusimprovethediffusionofchemicaltobulkofDIW,thisimprovestherinseefficiency.ThereisalsotheDIWMegasonicTank(overfloworwithquickdumprinse).TheextraMegasonicpowerhelpsparticlereductionandimprovesrinsingefficiencyespeciallyforviscouschemical.DIWTank171.DIWflow-rate.2.ProcessTime.3.DumpCycle&ProcessTimeforeachsequence.4.MegasonicOnSequence.CriticalParameters1830C,NH4OH:H2O2:H2O(1:2:50)Function:Particleremoval,LightpolymerremovalMechanism:oxidationandelectricalrepulsionOxidationDissolutionSurfaceetchingElectricalrepulsionOxidationmechanismElectricalrepulsionmechanismParticlecleanSC1(Standardclean1)H2O:H2O2:NH4OH(50:2:1)30oCH2ORinseRoomTempH2ORinseH2O:H2O2:HCl(50:1:1)30oCH2ORinseRoomTempDryerH2O:HF(100:1)23oC19SC1withMegasonicTransducerTransducerTransducerPartialwettingSolventdiffusingatinterfaceTotalwettingFloatingfreeBenefit:enhancetheparticleremoverate.Drawback:H2O2willbereducedduringoperation,whichcausesurfaceroughness!20ThemechanismproducingtheroughsurfaceistheNH4OHactsastheetchantoftheoxidewhileH2O2actsastheoxidant:SurfaceMicro-roughnessSiSiO2H2SiO42-(H3SiO4-,HSiO43-etc)V1V2HO2-OH-Path-1Path-2OH-V3V1=k1{HO2-}3k1=1.2x1014(65C)V2=k2{OH-}k2=5970(65C)V3=k3{OH-}2k3=2.0x109(65C)Path-1Path-2SiSubstrate21Methodsofreducingthemicroroughnesscanbesummarizedas:1.ReducetheproportionofNH4OH(theetchant)2.Reducethetemperatureofthebath3.ReducethecleaningtimeConventionalSC1:(1:1:5),70~80C22NH4OHevaporate&H2O2decomposeswithusageandtimeNH4OHlostinonehour:32%at5