化學(xué)機(jī)械拋光公開課一等獎市賽課獲獎?wù)n件

第八章化學(xué)機(jī)械拋光CMP(ChemicalMechanicalPlanarization)集成電路微細(xì)化旳追求：(1)高集成度(2)更快旳器件運營速度其中一種主流技術(shù)是二維構(gòu)造電流(多層化金屬布線)?；瘜W(xué)機(jī)械拋光旳主要性。在追求構(gòu)造微細(xì)化與多層布線旳趨勢中，存在幾種經(jīng)典旳技術(shù)難題。(1)辨別率和焦深旳折衷(2)表面平坦化減小臺階，提升鍍膜效果。表面平坦化旳問題舉例：用0.25mm工藝制作256MBDRAM，在利用兩層鋁金屬導(dǎo)線旳情況下，在存儲單元及外圍電路部分，高臺(存儲單元)和低地(外圍電路)兩者旳高度將相差約1mm，這對曝光機(jī)旳聚焦效果將造成影響。所以必須表面平坦化。（3）銅比鋁具有更佳旳導(dǎo)電率，是亞微米線寬旳電極布線旳理想材料。銅布線旳等離子體刻蝕極難實現(xiàn)，且效果較差。CMP技術(shù)是實現(xiàn)大馬士革構(gòu)造銅布線層旳關(guān)鍵工藝。DefinitionofPlanarizationPlanarizationisaprocessthatremovesthesurfacetopologies,smoothesandflattensthesurfaceThedegreeofplanarizationindicatestheflatnessandthesmoothnessofthesurfaceDefinitionofPlanarizationDefinitionofPlanarizationDegreesofPlanarizationPlanarizationSmoothingandlocalplanarizationcanbeachievedbythermalfloworetchback.Globalplanarizationisrequiredforthefeaturesizesmallerthan0.35mm,whichcanonlybeachievedbyCMP.ThermalFlowDielectricplanarization,PSGorBPSGHightemperature~1000℃BecomesoftandstarttoflowduetosurfacetensionSmoothandlocalplanarizationAsDepositedAfterPlanarizationProcess:EtchBackReflowtemperatureistoohighforsomematerials,suchasaluminumTwotype:SputteringetchbackPhotoresistetchbackSputteringetchbackArsputteringetchbackchipoffdielectricatthecornerofthegapandtapertheopeningsSubsequentCVDprocesseasilyfillsthegapwithareasonableplanarizedsurfaceReactiveetchbackprocesswithCF4/O2chemistryfurtherplanarizedthesurfaceCVD(I)Process:SputteringEtchBackProcess:CVD(II)Process:ReactiveEtchbackProcess:PhotoresistEtchbackPlanarizedsolidthinfilmonwafersurfacePlasmaetchprocesswithCF4/O2chemistryAdustingCF4/O2ratioallowto1:1ofoxidetoPRselectivityOxidecouldbeplanarizedafteretchbackAfterOxideDepositedProcess:PhotoresistCoatingandBakingProcess:PhotoresistEtchbackProcess:NecessityofCMPPhotolithographyresolutionR=K1l/NAToimproveresolution,NAorl

DOF=K2l/2(NA)2,bothapproachestoimproveresolutionreduceDOFHereweassumedK1=K2,l=248nm(DUV),andNA=0.6,Resolutionfor0.25mmDOF= and150nmfor0.18mmresolution208nmNecessityofCMP0.25mmpatternrequireroughness<2023?OnlyCMPcanachievethisplanarizationWhenfeaturesize>0.35mm,othermethodscanbeusedAdvantageofCMPPlanarizedsurfaceallowshigherresolutionofphotolithographyprocessTheplanarizedsurfaceeliminatessidewallthinningbecauseofpoorPVDstepcoverageUniformthinfilmdepositionReducedefectdensity,improveyieldDisadvantageofCMPIntroducedefectsofitsownNeedappropriatepost-CMPcleaningApplicationofCMPSTIformationDielectriclayerplanarizationTungstenplugformationCopperinterconnection(Damascenemethod)ApplicationofCMPCopperDepositedCMPCopperandTantalumChemicalMechanicalPolishingSystemPolishingpad,Wafercarrier,SlurrydispenserOrbitalPolishingWafercarrierPolishingPadPorous,flexiblepolymermaterialsPaddirectlyaffectsqualityofCMPPadmaterials:durable,reproducible,compressibleatprocesstemperatureSoftpad:betterwithinwaferuniformity,poorertopographicalselectivityHardpad:highremovalrate,longerconformalityrangeProcessrequirement:hightopographyselectivitytoachievesurfaceplanarizationToothbrushPadConditionerSweepsacrossthepadtoincreasethesurfaceroughnessrequiredbyplanarizationRemovestheusedslurryCMPSlurriesChemicalsintheslurryreactwithsurfacematerials,formchemicalcompoundsthatcanberemovedbyabrasiveparticlesParticulateinslurrymechanicallyabradethewafersurfaceandremoveunwantedcoatingSlurryimpactremovalrate,selectivity,planarityanduniformityToothpasteSlurryPolishingMechanismDifferentpolishingprocessneeddifferentslurries:Oxideremoval:alkalinesolutionwithsilicaMetalremoval:acidicsolutionwithalumina (Al2O3)SilicaParticulateOxideRemovalMechanismOH-bondsonbothfilmandsilicasurfaceFormhydrogenbondsofsilicaandfilmsurfaceFormmolecularbondsofsilicaandfilmsurfaceMechanicalremovaloftheparticlesbondswithwafersurfaceTearawayatomsfromfilmorwafersurfaceOxiedCMP,HydrogenBondOxideCMP,MoleculeBondOxideCMP,RemovalofOxideMetalRemovalMechanismMetalCMPprocessExample:CopperCMPDifficulttoplasmaetchcopperLackofvolatileinorganiccoppercompoundsHydrogengenerateeasilycauseexplosionCopperCMPkeyprocessincoppermetallizationprocessH2O2orHNO4canbeusedasoxidantAluminaparticulateisusedforaabrasionCopperCMPCuwasoxidedintoCuO,CuO2orCu(OH)2byoxidant(H2O2,HNO4,NH4OH))OxidationlayerwasremovedbyabrasionTheoxidantcontinuetooxidenewCulayer….CuO2isporousandcan’tformapassivationlayertostopfurthercopperoxidationAdditive(NH3)isneededtoenhancepasisivationtoreducewetetcheffectDishingeffectDishingeffectUsuallyhappensatalargeropeningareaLargemetalpadsMorematerialsareremovedfromthecentreCross-sectionviewlookslikeadishItisrelatedtotheremovalselectivityCopperCMPwithhighselectivityofCutoUSGcancausecopperdishingeffectCMPparametersRemovalrateUniformitySelectivityDefectsRemovalRateMechanicalremovalrateRwasfoundbyPrestonThePrestonequationcanbeexpressedasPrestonequationworksverywellforthebulkfilmpolishingprocessesTheprotrudingportionsonaroughsurfacehavehigherpolishingpressureRemovalrateofprotrudingpartsishigherThishelpstoremovesurfacetopographyandplanarizethesurfaceUniformityUsually49-points,3sstandarddeviationasthedefinitionoftheuniformityfortheCMPprocessqualificationsChangesofthefilmthicknessbeforeandafterCMPprocessismonitoredFortheproductionwafers,uniformityafterCMPprocessismonitoredNormallyuse9or13pointsmeasurementSelectivityRatioofremovalratesofdifferentmaterialsAffectCMPdefects,suchaserosionordishingTheslurrychemistryistheprimaryfactorthataffectsremovalselectivityofCMPSTIoxideCMPrequirehighoxidetonitrideselectivity,from100:1to300:1TungstenCMP,selectivitytooxideandTiNisveryimportantSlurrychemistry,oxidantSelectivityisalsorelatedtothepatterndensityHigherpatterndensity,lowerremovalselectivityLeadtoerosionofthetungstenandoxidefilmDefectsCMPremovesdefectsandimprovesyieldIntroducesomenewdefectsScratches,residual