IC工艺技术2--光刻

IC工艺技术系列讲座

第二讲PHOTOLITHOGRAPHY光刻讲座提要1. General2. Facility(动力环境)3. Mask(掩膜版)4. Processstephighlight(光刻工艺概述)5. BCD正胶工艺6. Historyand未来的光刻工艺1. GeneralMASKINGProcess(光刻工艺)Photolithography(光学光刻)----Transferatemporarypattern(resist)

Defectcontrol Criticaldimensioncontrol Alignmentaccuracy Crosssectionprofile

Etch(腐蚀)----Transferapermanentpattern(Oxide,Nitride,Metal…)2.0 FacilityrequirementTemperature(温度)70oFHumidity(湿度) 45%Positivepressure(正压) >0.02in/H2OParticlecontrol(微粒)Class100Vibration(震动)Yellowlightenvironment(黄光区)DIwater(去离子水)17mhomCompressairandNitrogen(加压空气,氮气)Inhousevacuum(真空管道)3.0 Mask(掩膜版)

DesignPGtapeMaskmaking

Plate---quartz,LEglass,SodalineglassCoating---Chrome,Ionoxide,EmulsionEquipment---E-beam,PatterngeneratorMaskstorage---AntistaticBoxPelliclePellicleprotection4.0 光刻工艺概述PrebakeandHMDS(前烘)Resistcoating(涂胶) EBR(去胶边),softbake,3. Exposure(曝光) Alignment(校正)4. Develop(显影) Poste-bake,Hardbake,backsiderinse5. Developinspection(显检)4.1 PrebakeandHMDStreatment

PurposeofPre-bakeandHMDStreatmentistoimprovetheresistadhesiononoxidewafer.HMDSisadhesionpromoterespeciallydesignedforpositiveresist. HMDS(Hexamethyldisilane)canbeappliedonthewafersby 1. Vaporinabucket 2. vaporinavacuumbox 3. Directlydispenseonwafer 4. YESsystem---inahotvacuumsystem 5. Vaporinahotplate(withexhaust) ToomuchHMDSwillcausepoorspin,viceversawillcauseresistlifting4.2 ResistCoating(涂胶)Resistcoatingspecification(指标）Thickness（厚度）0.7u–2.0u(3.0以上forPadlayer)Uniformity（均匀度）+50A–+200ASizeofEBR（去胶边尺寸）Particle（颗粒）<20perwaferBacksidecontamination(背后污染）三个主要因数影响涂胶的结果Resist Product(产品）

Viscosity（粘度）Spinner Dispensemethod（涂胶方法）

Spinnerspeed(RPM)（转速）

Exhaust（排气）

Softbaketemperature（烘温）Facility Temperature（室温）Humility（湿度）4.2.1 Coater(涂胶机）EquipmentmoduleandspecialfeaturePre-bakeandHMDS---Hot/ColdplateResistdispense---ResistpumpRPMaccuracy---MotorEBR---Top/bottomHotplate---softbaketemperatureaccuracyExhaustWastecollectionTemperature/HumiditycontrolhoodTransfersystem---ParticleandreliabilityProcessstepandprocessprogram---FlexibleSVG8800升降机涂胶HMDS热板冷板升降机升降机升降机涂胶热板热板升降机升降机升降机升降机涂胶热板冷板HMDS冷板冷板冷板涂胶热板热板升降机升降机显影热板热板热板冷板4.2.2Coater(涂胶机）combination4.2.3Coater(涂胶机）ResistdispensemethodsStaticDynamicRadialReverseradialResistpump(Volumecontrol---2cc/waferanddripping)Barrelpump---TritekDiaphragmpump---MilliporeN2pressurecontrolpump---IDLStepmotorcontrolpump---Cybotsizeofdispensehead4.2.4 Coater(涂胶机）rpm(转速）andacceleration（加速）

Maximumspeed---Upto10000rpmStability---daytodayAcceleration---controllablenumberofstepsReliability---timetoreplacementEBR(Edgebeadremoval)（清边）Method---TopEBRorBottomEBRorTopandbottomEBRProblem---DrippingChemical----Acetone,EGMEA,PGMEA,ETHLY-LACTATEResistTypeNegativeresistPositiveresist G-line i–line reverseimage TAC---topanti-reflectivecoating BARLI---bottomanti-reflectivecoatingChemicalamplificationresistXrayresist4.3 .1Exposure(曝光)

Transferapatternfromthemask(reticle)toresistGoal1. CriticalDimensioncontrol(CD)条宽2. Alignment校准---Mis-alignment,runin/out3. Patterndistortion图样变形---Astigmatism4. Crosssectionprofile侧面形貌---sidewallangle5. Defectfree无缺陷Equipment/mask/resistselection1. Resolution分辨率---Exposecharacter,Lightsource(wavelength),N/A,2. Auto-alignmentskill自动校准技术---Lightfield,darkfield,laser3. Mask掩膜版---e-beammaster,sub-master,spotsize,quartzplate,defectdensity,CDrequirement4. Resistselection胶选择4.3.2 Exposure(曝光)

AlignerTechnology1. Contactprint(接触） Softcontact,hardcontact,proximity2. Scanner(扫描）3. Stepper(重复） 1X,2X,4X,5X,10X4. Step–Scan(重复扫描) 4X---reticlemove,wafermove,reticle/wafermove5. Xray(X光）1:16. E-beam(电子束）---Directwrite4.3.3 Exposure(曝光)

Contactprint(接触）1. Mostofusefornegativeresistprocess---for5uprocessandcanbepushto3u.2. Positiveresistcanprintsmallerthan3u,anddeepUVcanpushto1u,butveryhighdefect3. Equipment: ---CanonPLA501 ---Cobilt ---Kasper ---K&SContactprint---Canon5014.3.4 Exposure(曝光)

Scanner(扫描）1. MostofuseforG–linePositiveresistprocess---for3uprocessandcanbepushto2u.2. Negativeresistcanprintsmallerthan4u3. Equipment: ---CanonMPA500,600 ---PerkinElmer100,200,300,600,700,900

PE240ScannerCanon600Scanner4.3.5 Exposure(曝光)Stepper(重复）

1. Glinepositiveresist---for<0.8uprocess2. ilinepositiveresist---<0.5uprocess3. ilineresistplusphase-shiftmask---canbepushedto0.354. deepUVresistprocess---0.35uandbelow5. Equipment: ---Ultratech ---Canon ---Nikon ---ASML 4.3.6 Exposure(曝光)6ASMLStepperlist

Model WavelengthResolutionASML2500 g 0.8ASML5000 ASML5500–20,22,25,60,60B,80,80B i 0.55ASML5500–100,100C,100D,150 i 0.45ASML5000–200,200B,250,250B UV 0.35ASML5500–300,300B,C,D,TFH UV 0.25ASML5500-900Step-Scan UV4.4.1 Develop(显影）Developprocess 1. Postexposebake 2. ResistDevelop 3. DIwaterrinse 4. HardBakeDevelopequipment 1. Batchdevelop 2. TrackdevelopDevelopchemical 1.

KOH 2. Metalfree(TMAH)--- Tetramethylamoniahydroxide 3. Wettingagent---with/without 4. Concentration---2.38%TMAHTrackdevelopmethod 1.

Spray 2. Steam 3. Signal-Paddle 4. Double-Paddle4.4.2Develop(显影）DevelopTrack1. TemperaturecontrolwaterjacketforDevelopline2. Developpump/developpressurecanister3. Exhaust4. Hotplatetemperaturecontrol5. Pre-wet---processprogram4.4.3 Develop(显影）CDcontrolindeveloping1. Postbakeprocess2. DevelopTime3. Concentrationofdeveloperchemical(Higherfast)4. Developertemperature(lowerfaster~1oC/0.1u)5. Developrecipe---pre-wet,paddle,rotation6. Ageofthedevelopchemical7. Rinse---DIwaterpressure8. Hardbaketemperature4.5.1 DevelopInspection

Toolforinspection1. Microscope Manuallyloading Automaticloading2. UVlamp Manuallyloading Automaticloading3. CDmeasurementequipment Manuallymeasuringsystem---Vicker, Automaticmeasuringsystem---Nanoline CDSEM4.5.2 DevelopInspection

Inspectionitems1. Layername2. Alignment3. Runin/out4. Patterndistortion5. Patternintegrity6. Defects lifting,particle,discoloration,scumming,bridging,excessresist,scratch7. CD(criticaldimension)

Nanoline---forCDmeasurementHitachi8860---CDSEMLeitzMicroscopeinspectstationAutoloadUVinspectionsystem

5.0 BCD正胶工艺Equipment SSI,SVG8800,SVG90Processstep pre-bake/HMDS/coldplate spin(<5000rpm)---dynamicdispense ---top(bottom)sideEBR(2mm) softbake(100oC)/cold/palteResist/spec Shipley 6112(1.2u) 1818(1.8u1stmetal) 6818(2.4u2ndmetal) 6118(2.9uPad) 6124(3.6u-4.5uST) Everlight 533(1.2) Uniformity---+300AResistcoating升降机冷板HMDS涂胶热板冷板升降机SVG90SVG88005.1.1 PositiveResist(正胶）Component(成分）Resin（树脂） Diazonaphthoquinone(DNQ)/novolakPhoto-sensitizer（感光剂）Solvent（溶剂）Dye（染料）Manufacturing(制造商）Kodak–Hunt–Ashchemical(USA)TOK(Japan)JSR(Japan)Shipley(USA)AZ(USA,Germany)Sumitomo(Japan)Everlight(Taiwan)5.1.2 PositiveResist(正胶）ProductNameandfeature(产品称与特性）以everlight(永光）正胶为例 ProductSeries EPG510Series Exposewavelength G-Line(435nm) Thickness Name 2000rpm5000rpm Viscosity（粘度） EPG510---12cp 1.25u 0.80u EPG512---21.5cp 2.00u 1.25u EPG516---50cp 3.25u 2.00u EPG518---105cp 4.50u 2.75u EPG519---460cp 9.00u 5.5u

Resolution(分辨率） 0.8u(0.55u---thesmallest) DepthofFocus(聚焦深度）+1.4u(1.0uline/space) Sensitivity(感光度） Eth=60mj/cm2

Eop=90mj/cm25.1.4 PositiveResist(正胶）Selectapositiveresist1. Resolution（分辨率）2. Resistthickness---Spincurve（厚度）3. Photospeed (曝光速度)4. Exposelatitude(曝光宽容度)5. Adhesion（粘附性）6. Reflectivenotch（反射缺口）6. Metalliccontent（金属含量）7. Thermalstability（热稳定性）8. Plasmaresistance（抗腐蚀能力）9. Howeasytoberemoved（清除能力）10. Price（價格）5.2 ExposeEquipmentUltratechstepper1100–(6”)

Ultratechstepper1500–(6”)

Canon600 –(6”)

PerkinElmer240 –(4”)PositiveResistreactionduringexposePositiveResistreactionduringexpose5.2.1 UltratechStepper

UltratechstepperG-lineN/A---0.24and0.311:1printratio3X5inchreticle---3,4,5,7field4udepthoffocusBlindstepcanbepushto<5u(nospec)Centerofarray<+50uDarkfieldalignmentSitebySitealignmentAlignmenttarget *oat---4mmX4mm *K/T---200uX200uUltratechStepper1100UltratechStepper1500/17005.2.2 UltratchstepperspecificationUTS---ReticleandJobfileGuideFiducialsUTS---primarylensUTSAlignment

OpticUlratechsteppersitebysitealignmentUTalignmentprocedureLoadjobfileintocomputerLoadreticleStartＦiducialsalignment---Guide,rotation(1500)OATalignment OATsize=4mmX4mm Fastandslowscan1000uSidebysidealignment Keyandtargetsize200uX200u shotscan20u longscan100u(80u)Auto-focus GobleorlocalFailurealignment Skip Expose Zmode5.3PerkinElmeralignerMicalignPE100MicalignPE200,220,240MicalignPE300,340,340HTMicalignPE500MicalignPE600MicalignPE700MicalignPE900Micscan100Micscan200Micscan300Micscan400PE240

SpecificationPE240PE240PMCenterofcurvatureParallelismLightintensityFocusDistortionMask/wafercenteringViewopticHPCrebuildCoolingairflowrateVibrationfromHPCFacilityVibrationfromenvironmentTemperaturecontrolhoodProcessReferencewaferApertureselectionResistbuilduponXYOpinsRoofmirrorcleaningMaskheatupduringexposePE---FocuswedgemaskPE---distortionPE---ProjectionopticPEMercurylampPE---AdjustableslitPEalignmentprocedureSetscanLoadmaskLoadwaferSwitchtomaskUsemicroscopeandcarriagemovementtofindthealignmentmarkonmask(Testdie)MovemaskonlytoalignthewaferSwitchtowaferMovewaferaligntomask5.4.1 ResistdevelopEquipment SSI,SVG8800,SVG90Processstep pose-ebake/coldplate develop---doublepaddle ---DIwaterrinse ---backN2/rinse hardbake(110-130oC)/cold/palteDeveloper TMAH2.35%

升降机冷板热板冷板升降机热板显影SVG8800SVG905.4.2ResistdevelopEquipment DevelopsinkEquipmentsetup Temperature N2blanket Filtersize Filterchange

Developer TMAH2.38% DevelopchangeProcessstep batchdevelop---immerse(1’&15”) QDRDIwaterrinse(8cycles) hardbake(110-130oC)/cold/palte6.Historyand未来的光刻工艺Willimprinttechnologyreplacephotolithography?In1798,imagewastransferredbystoneplate1940,BellLabusedresistdevelopedbyEastmanKodak1960,SanFranciscobayareabecomesthesiliconvalley---AT&T,Raytheon,Fairchild,Negativeresist–contactprintprocesswildlywasused.Endof1970-earlyof1980,positiveresist–Projectionprint(PerkinElmerMicalign)startedtobeusedinproduction.Bayareabecamecloudy---National,IntelandAMD.OutsidebayareahadMotolora,TI,IBM.From1970toearly2000,thetechnologyofsemiconductorisdevelopedveryfast.Thesmallestfeaturesizefrom10ureducedto0.09u.0.25uand0.35uproductswererunningmassproductioneverywhere---USA,Europe,Japan,Taiwan,Korea…i-line,anddeepUV---5Xstepperandstep-scan(4X)alignerbecamethemajortools.Now,0.09utechnologybecomemature.0.065u,0.045uand0.035utechnologyarebeingdeveloped.Immersionlithographyandimprinttechnologywillbeusedtoprintthesenanofeature.Imprinttechnologyclaimsthatitisabletoprint0.01u(10nm)---Itmaybethefuturemasking.6.1 History

Lithography,asusedinthemanufactureoftheintegratedcircuit,istheprocessoftransferringgeometricshapesonamasktothesurfaceofasiliconwafer.Theseshapesmakeupthepartsofthecircuit,suchasgateelectrodes,contactwindows,metalinterconnections,andsoon.Althoughmostlithographytechniquesusedtodayweredevelopedinthepast40years,theprocesswasactuallyinventedin1798;inthisfirstprocess,thepattern,orimage,wastransferredfromastoneplate(thewordlithocomesfrom).Thefirstpracticaltwodimensionaldevicepatterningonasiliconwaferwasactuallycarriedoutinthelate1940sattheBellLab.Atthattime,polyvinylcinnamate,developedbyEastmanKodak,wasusedasaresist.However,deviceyieldswerelowbecauseofthepooradhesionofthepolyvinylcinnamatetothesiliconandoxidesurface.TheKodakchemiststhenturnedtoasyntheticrubberbasedmaterial---apartiallycyclizedisopreneandaddedaUVactivesensitizer---abis-aryl-azideintoittocrosslinktherubbermatrixandcreatedanewclassofphotoresistmaterial.Sincetheunexposedareaofthenewmaterialwastheonlypartofthepolymermatrixthatwilldissolveinanorganicsolventandyieldinganegativeimageofthemaskplate,therefore,thenewmaterialwasthenreferredasthenegativeresist.Thecyclizedrubber/bisazideresistwaswidelyusedinthecontactprintingage.However,thecontactmodeofprintingcreatedseverewearofthemaskplateandthedefectdensityofthephotomaskandthewaferwasveryhigh.Theindustrythereforedecidedtoswitchtocontactlessprojectionprintingin1972forproducingthe16kDRAM.Projectionprinting,however,wascarriedoutintheFraunhofferorthesocalledfarfielddiffractionregionandtheaerialimagewasmuchpoorerthanthecontactorproximitymethodofprinting.Inordertopreservethesamequalityofimagestructure,thecontrastoftheimagematerialmustbeincreased.

Lithographiclorehasitthatthediazonaphthoquinone/novolakresist(thetermnovolakisderivedfromtheSwedishwordlak,meaninglacquerorresinandprefixedbytheLatinwordnovo,meaningnew)madetheirwayfromtheblueprintpaperindustrytothemicroelectronicthroughfamilyties:atthattimes,theofficesofAzoplate,theAmericanoutletforKalleprintingplate,waslocatedatMurrayHill,NJ,justacrossthestreetfromthefamousBellLabs.ThefatherofatechnicianatAzoplateworkedasatechnicianatBellLabs.ApparentlythefatherhadcomplainedonedayaboutthepoorresolutionqualityofthesolventdevelopedresistsystemusedattheBellLabsandthesonhadboastedthepropertiesoftheAzoplateDNQ/novolakmaterial;anyway,onedaythefathertookabottleofthematerialwithhimtotheBellLabs,andtheageoftheDNQ/novolakresistbegan.ThenewmaterialwasmarketedbyAzoplateunderthetradenameofAZphotoresist.Itwasalwaysreferredasthepositiveresistforapositivetoneofimagewouldbereproducedbythenewmaterial.TheuseofDNQ/novolaksystemincreasedrapidlyaftertheintroductionoftheprojectionlithography.By1980s,theDNQresisthadcompletelysupplantedtheoldnegativeresistastheworkhorseofthesemiconductorindustryinthehigh-endapplications.TheDNQ/novolakresisthasheldswayfor6devicegenerations,fromtheintroductionofthe16KDRAMtothelargescaleproductionofthe64MDRAMin1994to1995.Thesuccessofsuchmaterialwastheindicativeofitsupremeperformanceandpotential.Today,itappearsthatitisnotreallytheresolutionwhichdefinesthelimitoftheDNQ/novolakresistapplication,butratherthelossinthedepthoffocuswiththeeverincreasingNAofthestepper.DeepUVandchemicalamplificationnegativetoneresistslowlyerodethemarketplaceoftheDNQ/novolakresist.Bytheendofthe1990s,theDNQ/novolakresistwasnolongerbeusedinthetechnologicallymostadvancedapplications---theprintingofthecriticallevelsofthe256MDRAM.6.2Future

IntroductionofnanoimprinttechnologyFabricatingmicrostructuresandnanostructureisimportantinmanyfieldsofscienceandtechnology,includingelectronics,datastorage,flexibledisplays,microelectromechanicalsystems,microfluidics,photonicsandbiosensors.Traditionally,opticalorelectronbeamlithographysystemsareusedtoprinttherelevantstructures.However,newprintingmethodssuchasimprintlithographyandsoftlithographyhaverecentlybeenexploredinsomedetailtolowerthecostsoffabricatinglowvolumesofstructureswithverysmallfeaturesandtoincreasetherangeofprintingapplication.Thesoftlithographyschemes,ingeneral,useasofttemplatepatternmadeofsiliconeelastomer,polydimethylsiloxane(PDMS),whichisplacedintocontactwiththesubstrateinavarietyofways,topatternasurfacefilm,totransferamaterial,orfordirectintegrationintothefinalpart,witharangeofinnovativeapplications.ChallengesinthisareaaregenerallyconcernedwiththeinherentlimitationsofthePDMSmaterialincludingresolutionlimitationswhencuringduetodifferencesinthermalexpansionbetweenthemasterandmold;adhesiontocommonmastermaterialslikesilicon;significanttime,aboutanhour,tofabricatea