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1、 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaSemiconductor Semiconductor Manufacturing TechnologyManufacturing TechnologyMichael Quirk&Julian Serda Michael Quirk&Julian Serda October 2001 by Prentice HallOctober 2001 by Prentice HallChapter 14Chapter 1
2、4 Photolithography:Photolithography:Alignment and ExposureAlignment and Exposure 2000 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian Serda 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaObjectivesAfter studying the mater
3、ial in this chapter,you will be able to:1.Explain the purpose of alignment and exposure in photolithography.2.Describe the properties of light and exposure sources important for optical lithography.3.State and explain the critical aspects of optics for optical lithography.4.Explain resolution,descri
4、be its critical parameters,and discuss how it is calculated.5.Discuss each of the five equipment eras for alignment and exposure.6.Describe reticles,explain how they are manufactured and discuss their use in microlithography.7.Discuss the optical enhancement techniques for sub-wavelength lithography
5、.8.Explain how alignment is achieved in lithography.2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaEight Basic Steps of PhotolithographyTable 14.1 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaThree Functions
6、of the Wafer Stepper1.Focus and align the quartz plate reticle(that has the patterns)to the wafer surface.2.Reproduce a high-resolution reticle image on the wafer through exposure of photoresist.3.Produce an adequate quantity of acceptable wafers per unit time to meet production requirements.2001 by
7、 Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaReticle Pattern Transfer to ResistSingle field exposure,includes:focus,align,expose,step,and repeat processUV light sourceReticle(may contain one or more die in the reticle field)ShutterWafer stage controls position
8、 of wafer in X,Y,Z,)Projection lens(reduces the size of reticle field for presentation to the wafer surface)Shutter is closed during focus and alignment and removed during wafer exposureAlignment laserFigure 14.1 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian
9、SerdaLayout and Dimensions of Reticle Patterns4)Poly gate etch1)STI etch2)P-well implant3)N-well implant8)Metal etch5)N+S/D implant6)P+S/D implant7)Oxide contact etchTop view12345768Cross sectionResulting layersFigure 14.2 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk a
10、nd Julian SerdaOptical LithographyLightInterference of Light WavesOptical FiltersElectromagnetic Spectrum 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaLight Wavelength and FrequencyvfLaserv=velocity of light,3 108 m/secf=frequency in Hertz(cycles per se
11、cond)=wavelength,the physical length of one cycle of a frequency,expressed in metersFigure 14.3 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaWave InterferenceABA+BWaves in phaseWaves out of phaseConstructiveDestructiveFigure 14.4 2001 by Prentice HallSe
12、miconductor Manufacturing Technologyby Michael Quirk and Julian SerdaOptical FiltrationSecondary reflections(interference)Coating 1(non-reflecting)Coating 3GlassCoating 2Reflected wavelengthsTransmitted wavelengthBroadband lightFigure 14.5 2001 by Prentice HallSemiconductor Manufacturing Technologyb
13、y Michael Quirk and Julian SerdaUltraviolet Spectrum(nm)700455060065050045040035030025020015010050Ultraviolet spectrumVisible spectrumMercury lampExcimer laserPhotolithography light sourcesghi36540524819313436157126VioletRedBlueGreenYellow OrangeMid-UVEUVDUVVUVFigure 14.6 2001 by Prentice HallSemico
14、nductor Manufacturing Technologyby Michael Quirk and Julian SerdaOptical LithographyExposure SourcesMercury Arc LampExcimer LaserSpatial CoherenceExposure Control 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaEmission Spectrum of Typical High Pressure Me
15、rcury Arc Lamp120100806040200200300 400 500 600Wavelength(nm)Relative Intensity(%)h-line405 nmg-line436 nmi-line365 nmDUV248 nmEmission spectrum of high-intensity mercury lampMercury lamp spectrum used with permission from USHIO Specialty Lighting ProductsFigure 14.7 2001 by Prentice HallSemiconduct
16、or Manufacturing Technologyby Michael Quirk and Julian SerdaMercury Arc Lamp Intensity PeaksTable 14.2 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaSpectral Emission Intensity of 248 nm Excimer Laser vs.Mercury Lamp100806040200Relative Intensity(%)KrF l
17、aser280210240260220Wavelength(nm)Hg lampFigure 14.8 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaExcessive Resist Absorption of Incident LightPhotoresist(after develop)SubstrateSloping profileFigure 14.9 2001 by Prentice HallSemiconductor Manufacturing
18、Technologyby Michael Quirk and Julian SerdaExcimer Laser Sources for Semiconductor PhotolithographyTable 14.3 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaSpatial CoherenceIncoherent light sourceof a single wavelengthSlitCoherent cylindrical wave frontT
19、wo coherent cylindrical wave frontsInterference patternsTwo slitsclosely spacedBlack box illuminatorFigure 14.10 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaOptical LithographyOpticsReflection of LightRefraction of LightLensDiffractionNumerical Apertur
20、e,NAAntireflective Coating 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaLaw of ReflectionirIncident lightReflected lightLaw of Reflection:i r The angle of incidence of a light wavefront with a plane mirror is equal to the angle of reflection.Figure 14.1
21、1 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaApplication of MirrorsUsed with permission from Canon USAMaskFlat mirrorEllipsoidal mirrorFlat mirrorIlluminator for a simple alignerFigure 14.12 2001 by Prentice HallSemiconductor Manufacturing Technologyb
22、y Michael Quirk and Julian SerdaRefraction of Light Based on Two MediumsSnells Law:sin i=n sin r Index of refraction,n=sin i/sin r air(n 1.0)glass(n 1.5)fast mediumslow medium air(n 1.0)glass(n 1.5)fast mediumslow mediumFigure 14.13 2001 by Prentice HallSemiconductor Manufacturing Technologyby Micha
23、el Quirk and Julian SerdaAbsolute Index of Refraction for Select MaterialsTable 14.4 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaOptical System of LensesMercury lampLamp position knobLamp monitorEllipsoidal mirrorShutterFlys eye lensFlat mirrorMasking
24、unitMirrorMirrorCollimator lensCondenser lensCondenser lensOptical filterFiber opticsReticleReticle stage(X,Y,)Projection opticsOptical focus sensorInterferometer mirrorX-drive motorY-drive motor-Z drive stageVacuum chuckWafer stage assemblyLight sensorIlluminator assemblyUsed with permission from C
25、anon U.S.A.,FPA-2000 i1 exposure systemFigure 14.14 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaConverging Lens with Focal PointOFFSSf2ff=focal lengthF=focal pointS=2fO=origin,center of lensReal imageObjectFigure 14.15 2001 by Prentice HallSemiconducto
26、r Manufacturing Technologyby Michael Quirk and Julian SerdaDiverging Lens with Focal PointOFFSSVirtual imageObjectf=focal lengthF=focal pointS=2fO=origin,center of lensFigure 14.16 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaLaser-Induced Lens Compacti
27、onCompacted area of lensFigure 14.17 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaInterference Pattern from Light Diffraction at Small OpeningLight travels in straight lines.Diffraction occurs when light hits edges of objects.Diffraction bands,or interf
28、erence patterns,occur when light waves pass through narrow slits.Diffraction bandsFigure 14.18 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaDiffraction in a Reticle PatternSlitDiffracted light raysPlane light waveFigure 14.19 2001 by Prentice HallSemico
29、nductor Manufacturing Technologyby Michael Quirk and Julian SerdaLens Capturing Diffracted LightUV012341234LensQuartzChromeDiffraction patternsMaskFigure 14.20 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaEffect of Numerical Aperture on ImagingFigure 14
30、.21 Exposure lightLens NAPinhole masksImage resultsDiffracted lightGoodBadPoor 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaTypical NA Values for Photolithography ToolsTable 14.5 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quir
31、k and Julian SerdaPhotoresist Reflective Notching Due to Light ReflectionsPolysiliconSubstrateSTISTIUV exposure lightMaskExposed photoresistUnexposed photoresistNotched photoresistEdge diffractionSurface reflectionFigure 14.22 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Qui
32、rk and Julian SerdaIncident and Reflected Light Wave Interference in Photoresist Standing waves cause nonuniform exposure along the thickness of the photoresist film.Incident waveReflected wavePhotoresistFilmSubstrateFigure 14.23 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael
33、Quirk and Julian SerdaEffect of Standing Waves in PhotoresistPhotograph courtesy of the Willson Research Group,University of Texas at AustinPhoto 14.1 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaAntireflective Coating to Prevent Standing Waves The use
34、of antireflective coatings,dyes,and filters can help prevent interference.Incident waveAntireflective coatingPhotoresistFilmSubstrateFigure 14.24 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaLight Suppression with Bottom Antireflective CoatingBARCPolysi
35、liconSubstrateSTISTIUV exposure lightMaskExposed photoresistUnexposed photoresistFigure 14.25 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaBARC Phase-Shift Cancellation of Light(A)Incident lightPhotoresistBARC(TiN)AluminumC and D cancel due to phase dif
36、ference(B)Top surface reflection(C)(D)Figure 14.26 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaTop Antireflective CoatingIncident lightPhotoresistResist-substrate reflectionsSubstrateIncident lightPhotoresistSubstrate reflectionSubstrateTop antireflect
37、ive coating absorbs substrate reflections.Figure 14.27 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaOptical LithographyResolutionCalculating ResolutionDepth of FocusResolution Versus Depth of FocusSurface Planarity 2001 by Prentice HallSemiconductor Man
38、ufacturing Technologyby Michael Quirk and Julian SerdaResolution of FeaturesThe dimensions of linewidths and spaces must be equal.As feature sizes decrease,it is more difficult to separate features from each other.Figure 14.28 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Qui
39、rk and Julian SerdaCalculating Resolution for a given,NA and kLens,NAWaferMaskIlluminator,Rk=0.6R365 nm 0.45 486 nm365 nm 0.60365 nm193 nm 0.45257 nm193 nm 0.60193 nmi-lineDUV k NAR=Figure 14.29 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaDepth of Focu
40、s(DOF)+-PhotoresistFilmDepth of focusCenter of focusCenter of focusLensFigure 14.30 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaResolution Versus Depth of Focus for Varying NA 2(NA)2DOF =PhotoresistFilmDepth of focusDepth of focusCenter of focus+-Lens,
41、NAWaferMaskIlluminator,DOFR DOF365 nm 0.45 486 nm901 nm365 nm 0.60365 nm507 nm193 nm 0.45257 nm476 nm193 nm 0.60193 nm268 nmi-lineDUVFigure 14.31 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaPhotolithograhy EquipmentContact AlignerProximity AlignerScann
42、ing Projection Aligner(scanner)Step-and-Repeat Aligner(stepper)Step-and-Scan System 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaContact/Proximity Aligner SystemIlluminatorAlignment scope(split vision)MaskWaferVacuum chuckMask stage(X,Y,Z,)Wafer stage(X
43、,Y,Z,)Mercury arc lampUsed with permission from Canon USA,Figure 14.32 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaEdge Diffraction and Surface Reflectivity on Proximity AlignerUVMaskDiffraction of light on edges results in reflections from underside o
44、f mask causing undesirable resist exposure.UV exposure lightSubstrateResistDiffracted and reflected lightGapMaskSubstrateFigure 14.33 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaScanning Projection AlignerRedrawn and used with permission from Silicon V
45、alley Group LithographyMaskWaferMercury arc lampIlluminator assemblyProjection optics assemblyScan directionExposure light(narrow slit of UV gradually scans entire mask field onto wafer)Figure 14.34 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaStep-and-
46、Repeat Aligner(Stepper)Used with permission from Canon USA,FPA-3000 i5(original drawing by FG2,Austin,TX)Figure 14.35 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaStepper Exposure FieldUV lightReticle field size20 mm 15mm,4 die per field5:1 reduction le
47、nsWaferImage exposure on wafer 1/5 of reticle field4 mm 3 mm,4 die per exposureSerpentine stepping patternFigure 14.36 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaWafer Exposure Field for Step-and-Scan5:1 lensUVUVStep and ScanImage FieldScanStepperImag
48、e Field(single exposure)4:1 lensReticleReticleScanScanWaferWaferStepping directionRedrawn and used with permission from ASM LithographyFigure 14.37 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaStep and Scan Exposure SystemIlluminator opticsBeam lineExci
49、mer laser(193 nm ArF)Operator console4:1 Reduction lens NA=0.45 to 0.6Wafer transport systemReticle stageAuto-alignment systemWafer stageReticle library(SMIF pod interface)Used with permission from ASML,PAS 5500/900Figure 14.38 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Qu
50、irk and Julian SerdaReticlesComparison of Reticle Versus MaskReticle MaterialsReticle Reduction and SizeReticle FabricationSources of Reticle Damage 2001 by Prentice HallSemiconductor Manufacturing Technologyby Michael Quirk and Julian SerdaComparison of Reticle Versus MaskTable 14.6 2001 by Prentic