WETProcessIntroduction PurposeofWetCleaningProcess Throughtoaseriesofprocessestomakethewafersfreefromparticles organiccontaminations metalcontamination surfacemicroroughnessandnativeoxideusingsomekindsofchemicalsincludingDIW PurposeofWetCleaningProcess ForEtchingprocessOxideremove Nitrideremove Photoresist polymerremove ForCleaningprocessFreeofparticles Freeofmetalion Freeoforganic Freeofmicro roughness Freeofnativeoxide WetCleaning Pre treatment WetCleaning Post treatment ResistRemoval Diffusion CVD PVD Lithography Etching Doping WaferIn WaferOut ICProcessing WetProcess 1 FEOLpost ashclean35 typicalSPM trendistointegrateresiststripingandcleaning 2 Pre diffusionclean30 RCAclean trendistousedilutechemistriestoreducecost improveequipmentreliabilityandprocessperformance 3 BEOLpost etchclean20 issueswithtechnical cost environment trendistousesinglewaferdryclean4 Others PostCMPandspecialcleaning 15 SC1basedcleaning ChemicalsInvolved Wetbench PurposeofPre cleanistoremovethelastunwantedoxidelayerandpreparesurfacefreeofmetalliccontaminantsandgoodPCfornextoxidation Pre diffusionclean RCAclean SiO2 s 6HF l H2SiF6 l 2H2O l Theetchrate orreactionrateofHFwithoxide canbeslowedbyaddingmorewaterandlowerstheconcentrationofHF HFwilletchBPSG Oxide Nit Si H2O HF100 1 50 1 49 Function RemoveOxide SiO2 Mechanism ReactswithOxideandformasolvablebyproduct OxideEtchHF EtchingoffnativeoxideleavinghydrophobicSisurface repelsH2O thatispronetoH2OmarkAsamethodtopassivatesurface H2O2 SC1 SC2lastisused AftercleaningHFonSi theSiwaferhasH2SiF6 itischargedupwithSiF62 ions thishashighaffinitytoattractdefects duetostrongpolarity WhatisH2Omark ItissomeH2OstainwhichoxidisestheSisurface ItcanalsobeaconcentrationofH2Ocontaminants H2Oattractedarea easytocreateH2Omark ox ox Siwafer Whatistheimpactofwatermark Watermarkcancauseproblemswithadhesionoffilms contactresistance non uniformitybetweenconductinglayers blocketch gateoxidedefects Howtopreventit Treatthewafersurfacewitheg H2O2 SC1 SC2 someoxidationeffects toensurehydrophilicsurfacethroughout EnsuredryersperformanceVaporJetdryerLowpressureDryerSpinDryerMicroMistDryer DIwaterisDe ionizedwater WaterRinse DIWater DIWtankisforrinsingwaferascleanaspossiblebeforegoingintothenextchemicaltanktopreventcross contaminationorbeforeleavingthehood DIWcanoverfloworquickdumprinse QDR OverflowisverystableflowofDIWandgivesgoodPCcontrol Itmakesuseofdiffusionanddilution QDR ontheotherhandmakesuseofextradragforcewhenDIWdump itisfastatremovingacidtrace butsincethereismoreagitationinthetank itmayresultinhigherPC ControloftheDIWtankandsurroundingcleanlinessisimportant DIWtankoverflowsatalltimeswithby passflowtopreventbacteria BacteriawillresultinPC metalliccontamination DIWTank DIWcanbehotorcold dependsonpreviousandnexttanks HotChemicalwillbefollowedbyHotDIW ColdDIW thisistopreventthermalshock Forhighviscositychemical HDIWrinsewillimprovesolubilityofthechemical thusimprovethediffusionofchemicaltobulkofDIW thisimprovestherinseefficiency ThereisalsotheDIWMegasonicTank overfloworwithquickdumprinse TheextraMegasonicpowerhelpsparticlereductionandimprovesrinsingefficiencyespeciallyforviscouschemical DIWTank DIWflow rate ProcessTime DumpCycle ProcessTimeforeachsequence MegasonicOnSequence CriticalParameters 30C NH4OH H2O2 H2O 1 2 50 Function Particleremoval LightpolymerremovalMechanism oxidationandelectricalrepulsion Oxidation Dissolution Surfaceetching Electricalrepulsion Oxidationmechanism Electricalrepulsionmechanism ParticlecleanSC1 Standardclean1 SC1withMegasonic Transducer Transducer Transducer Partialwetting Solventdiffusingatinterface Totalwetting Floatingfree Benefit enhancetheparticleremoverate Drawback H2O2willbereducedduringoperation whichcausesurfaceroughness ThemechanismproducingtheroughsurfaceistheNH4OHactsastheetchantoftheoxidewhileH2O2actsastheoxidant SurfaceMicro roughness Si H2SiO42 H3SiO4 HSiO43 etc V1 V2 HO2 OH Path 1 Path 2 OH V3 V1 k1 HO2 3k1 1 2x1014 65C V2 k2 OH k2 5970 65C V3 k3 OH 2k3 2 0 x109 65C Path 1 Path 2 SiSubstrate Methodsofreducingthemicroroughnesscanbesummarizedas ReducetheproportionofNH4OH theetchant ReducethetemperatureofthebathReducethecleaningtimeConventionalSC1 1 1 5 70 80C NH4OHevaporate44 at70 H2O2decompositionisastrongfunctionofmetalioncontent SC1BathLifeProblems HeaterBurnt InlineheaterismadeofQuartzandSC1etchesSi thusinlineheaterhaslifetime Ifburntandleaking therecanbemetalcontaminationslikeALandFe NH4OHandH2O2willdegradeandcausebubbling mayresultinstreakdefectsonthewafer CommonIssueswithSC1 Togetridofbubbles Tiltwafertofacebackm c Slightagitationofwaferstoreleasebubblefromwafersurfacem c Bubblecollapser degaser CommonIssueswithSC1 30C HCl H2O2 H2OFunction IonicandMetallicContaminationRemoval MetalliccleanSC2 Standardclean2 Mechanism HCLreactswithmetaltoformasolublesaltwhichisremovedfromwafersurfacebydissolvinginH2O AsfarasH2O2 itpassivitytheactivesurface HCl H2O2arenoteasytobeproducedtobeultracleanandassuch thechemicalitselfhavesomemetallic WhendilutedSC2isused metallicfromwafercan