Extending-immersion-lithography-down-to-1x-nm-prod

62002200420062008201020122014201620182020YearofProductionstart*Note:Processdevelopment1.52yearsinadvanceAa+40O.w3020AI:1awnNXT:1950iNXE:3100-pNXE:3300BNXT:1960BiNXT:1970Ci4LE=Litho-Etch,n=numberofiterationsSADP=SelfAlignedDoubiePatterningSAQP=SelfAlignedQuadruplePatterning+AT:1200ç80tH6050:,a,2DLEnPatterningL1DSADPO1DSAQP200inn`-NAND17%/DRAM13.9%/Logic14.1%ESingleExposureExtendingimmersionlithographydownto1xnmproductionnodesWimdeBoeij,RemiPieternella,IgorBouchoms,MartijnLeenders,MarjanHoofman,RoelofdeGraaf,HaicoKok,ParBroman,JoostSmits,Jan-JaapKuit,MatthewMcLarenASMLNetherlandsB.V.,DeRun6501,5504DRVeldhoven,TheNetherlandsABSTRACTInthispaperwereportontheperformanceenhancementsontheNXTimmersionscannerplatformtosupporttheimmersionlithographyroadmap.Weparticulardiscussscannermodulesthatenablefutureoverlayandfocusrequirements.Amongotherswedescribetheimprovementsingridcalibrationsandgridmatching;thermalcontrolofreticleheatingwithdynamicsystemsadjustments;aberrationtuningandFlexWave-lensheatingcontrolaswellasaberration-andoverlay-metrologyonwafer-2-wafertimescales.Finallyweaddressreductionoflevelingprocessdependencies,stageservodynamicsandwafertableflatnesstoenhanceon-productfocusandlevelingperformance.Wepresentanddiscussmodule-andsystem-dataoftheabovementionedscannerimprovements.Keywords:Immersionlithography,exposuresystems,ArF,overlay,imaging,focus.1.INTRODUCTIONHistoricallythelithographyresolutionroadmapwasdrivenbynumericalaperture(NA)andwavelengthoftheexposureopticsinsteppers&scanners(Figure1).Supplementedwithvariouslow-k1imagingenhancementmethods[1]featureprintinghasbeenpushedclosetothetheoreticallimitsofk1=0.25.Withtheintroductionofmultiplepatterningtechniques[2,3]theopticsinthehigh-endimmersionscannersisnolongertheprimedriverinattainableultimateresolution(e.g.halfpitch).Neverthelesstheimmersionscannerstillprovidestheessentialbackboneinpatterningschemes,enablingsub-resolutionprintingincombinationwithdouble(&quadruple)patterningmethodsandmultiplemask-split/multi-exposure/etchsequences.Whenprogressingonthelithographypathtoevensmallerfeatures,patternplacementrequirementsandlayer-to-layeroverlayrequirementskeepprogressivelyscalingwithresolutionnodes.Theseoverlayandfocusrequirementskeepdrivingmoduleenhancementsandsystemimprovementsinimmersionscannerssystems.Figure1.Graphicalrepresentationoftherequiredresolution(half-pitch)fromthelithographyroadmapforthethreeapplicationareas(NAND/DRAM/Logic).ThesoliddotsindicatethevariousXT/NXT/NXEscannertoolssupportingtheindustryresolutionneeds.Opencircles/triangles/diamondsindicatescannerlithosolutionswhenemployinglitho-etchcombinations,doublepatterningandquadruplingpatterningmethods.Inthispaperwereflectonthestate-oftheartNXTimmersion(ArFi)scannersandelaborateonthescannerchangesmovingforward.OpticalMicrolithographyXXVI,editedbyWillConley,Proc.ofSPIEVol.8683,86831L©2013SPIE·CCCcode:0277-786X/13/$18·doi:10.1117/12.2021397Proc.ofSPIEVol.868386831L-1DownloadedFrom::)FullWaferCDU40nm[solinesed)FullWaferFoy1IIII.uilll.ili.Ii.nul.11..i1.AiInusUniformity(FU)11,11.1,11.10a)DedicatedChuckOverlay(DCO)hiveOverlayb)MatchedMac2.230WPHNXTIMMERSIONSCANNERPERFORMANCEForseveralyearsnowthesemiconductorindustryisusingNXTimmersionscannersinhighvolumemanufacturing.Thescannerbuildsonthedualstage1.35NAimmersiontechnology,TWINSCANXT:1900iintroducedin2007[4].ContrarytheXTsystemsthatusetraditionalstageinterferometers,TWINSCANNXT:1950i[5-8]incorporatesanencoder-basedstagepositioningplatform.Thereducedbeamlengthintheseencodersystemsareknowntobemorerobusttothermalconditioningperturbationsandenableenhancedaccuracyandreproducibilityasisreflectedinthetotalsystemoverlay.Theproductivityofthissystemiscurrentlyreachinglevelsof230waferperhour(wph)andistheworkhorsein3x-nmand2x-nmnodevolumeproduction.Asnapshotofthekeyperformanceparameters(Imaging,OverlayandFocus)ofthe230wph-toolsisdepictedinFigure2.Figure2.Keyperformanceparametersofthe230wphNXTscanners.NXT:1950i(bluebars)andNXT:1960Bi(greenbars).a)DedicatedChuckOverlay,b)MatchedMachineOverlayOverlay,c)FullwaferCDUfor40nmisolatedlinesandd)fullwaferFocusuniformityaredepicted.NotethattheNXT:1960BiMMOvaluesaregivenforthefullwaferBMMOoverlaymetricandMMOdatafortheNXT:1950iisbasedoninnerfields(inset).TheNXT:1950itoolsconsistentlyachieve5.5nmfullwafermachinetomachineoverlaymatching(figure2).Thishasbeenmadepossiblebyreducingthesystematicoverlaygridfingerprintbyimprovingabsolutegridcalibrationsandmechanicalandthermalstabilityofthewaferstageandreticlepositioningmodules.Theseimprovementsalleviatetheneedfortooldedication,andevenchuckdedication,thepreferredoperationmodeinvolumeproductionforoptimaltoolutilization.Notethatalltheseimaging,focus&overlayparameterscanbesustainedatthe230wphproductivitylevels.Theuseofimmersiontechnologyathighproductivitylevelsalsoputsstrongdemandsonin-scannerimmersiondefectcontrol.Theheartofthe230wphNXT:1950iimmersionsystemconsistsofanair-dragbasedimmersionhoodwhichha