SMT-14~1

©2001byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerdaSemiconductorManufacturingTechnologyMichaelQuirk&JulianSerda©October2001byPrenticeHallChapter14Photolithography:AlignmentandExposure©2000byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerda©2001byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerdaObjectivesAfterstudyingthematerialinthischapter,youwillbeableto:1.Explainthepurposeofalignmentandexposureinphotolithography.2.Describethepropertiesoflightandexposuresourcesimportantforopticallithography.3.Stateandexplainthecriticalaspectsofopticsforopticallithography.4.Explainresolution,describeitscriticalparameters,anddiscusshowitiscalculated.5.Discusseachofthefiveequipmenterasforalignmentandexposure.6.Describereticles,explainhowtheyaremanufacturedanddiscusstheiruseinmicrolithography.7.Discusstheopticalenhancementtechniquesforsub-wavelengthlithography.8.Explainhowalignmentisachievedinlithography.©2001byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerdaEightBasicStepsofPhotolithographyStepChapterCovered1.Vaporprime132.Spincoat133.Softbake134.Alignmentandexposure145.Post-exposurebake156.Develop157.Hardbake158.Developinspect15Table14.1©2001byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerdaThreeFunctionsoftheWaferStepper1.Focusandalignthequartzplatereticle(thathasthepatterns)tothewafersurface.2.Reproduceahigh-resolutionreticleimageonthewaferthroughexposureofphotoresist.3.Produceanadequatequantityofacceptablewafersperunittimetomeetproductionrequirements.©2001byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerdaReticlePatternTransfertoResistSinglefieldexposure,includes:focus,align,expose,step,andrepeatprocessUVlightsourceReticle(maycontainoneormoredieinthereticlefield)ShutterWaferstagecontrolspositionofwaferinX,Y,Z,q)Projectionlens(reducesthesizeofreticlefieldforpresentationtothewafersurface)ShutterisclosedduringfocusandalignmentandremovedduringwaferexposureAlignmentlaserFigure14.1©2001byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerdaLayoutandDimensionsofReticlePatterns4)Polygateetch1)STIetch2)P-wellimplant3)N-wellimplant8)Metaletch5)N+S/Dimplant6)P+S/Dimplant7)OxidecontactetchTopview12345768CrosssectionResultinglayersFigure14.2©2001byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerdaOpticalLithographyLight•InterferenceofLightWaves–OpticalFilters•ElectromagneticSpectrum©2001byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerdaLightWavelengthandFrequency=vfLaserv=velocityoflight,3´108m/secf=frequencyinHertz(cyclespersecond)=wavelength,thephysicallengthofonecycleofafrequency,expressedinmetersFigure14.3©2001byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerdaWaveInterferenceABA+BWavesinphaseWavesoutofphaseConstructiveDestructiveFigure14.4©2001byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerdaOpticalFiltrationSecondaryreflections(interference)Coating1(non-reflecting)Coating3GlassCoating2ReflectedwavelengthsTransmittedwavelengthBroadbandlightFigure14.5©2001byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerdaUltravioletSpectrum(nm)700455060065050045040035030025020015010050UltravioletspectrumVisiblespectrumMercurylampExcimerlaserPhotolithographylightsourcesghi36540524819313436157126VioletRedBlueGreenYellowOrangeMid-UVEUVDUVVUVFigure14.6©2001byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerdaOpticalLithographyExposureSources•MercuryArcLamp•ExcimerLaser–SpatialCoherence•ExposureControl©2001byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerdaEmissionSpectrumofTypicalHighPressureMercuryArcLamp120100806040200200300400500600Wavelength(nm)RelativeIntensity(%)h-line405nmg-line436nmi-line365nmDUV248nmEmissionspectrumofhigh-intensitymercurylampMercurylampspectrumusedwithpermissionfromUSHIOSpecialtyLightingProductsFigure14.7©2001byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerdaMercuryArcLampIntensityPeaksUVLightWavelength(nm)DescriptorCDResolution(m)436g-line0.5405h-line0.4365i-line0.35248DeepUV(DUV)0.25Table14.2©2001byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerdaSpectralEmissionIntensityof248nmExcimerLaservs.MercuryLamp100806040200RelativeIntensity(%)KrFlaser280210240260220Wavelength(nm)HglampFigure14.8©2001byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerdaExcessiveResistAbsorptionofIncidentLightPhotoresist(afterdevelop)SubstrateSlopingprofileFigure14.9©2001byPrenticeHallSemiconductorManufacturingTechnologybyMichaelQuirkandJulianSerdaExcimerLaserSourcesforSemiconductorPhotolithographyMaterialWavelength(nm)Max.Output(mJ/pulse)Frequency(pulses/sec)PulseLength(ns)CDResolution(m)KrF248300–1500500250.25ArF193175–300400150.18F2157610200.15Table14.3©2001byPrenticeHallSemiconductor