微电子工艺课件总结

课程总结前言&拉单晶ComparisonoftheSemiconductorsMaterialBandgapdescriptionGe0.66eVEarliestsemiconductor，Firsttransistorin1947Si1.12eVMostcommonsemiconductor；Easytoformhighqualityoxidizedlayer；LargerbandgapthanGe，Higherworkingtemperature；Cheap.GaAs1.42eVHigherelectronmobility，Goodforhighspeeddevices；Poorthermalstability，Highdefectdensity，lowintrinsicoxidizationrateCleanroomclassifications

USFEDSTD209EcleanroomstandardsClassmaximumparticles/ft3ISO

equivalent≥0.1

µm≥0.2

µm≥0.3

µm≥0.5

µm≥5

µm1357.5310.007ISO3103507530100.07ISO41003,5007503001000.7ISO51,00035,0007,50030001,0007ISO610,000350,00075,00030,00010,00070ISO7100,0003.5×106750,000300,000100,000700ISO8

MostlyUsed!DopingintheSiliconGrowthProcessP-typedopant:BoronN-typedopant:PhosphorInthedopingprocess,thedopantconcentrationisdifferentinthecrystalandinthemeltedSi，expressedwiththeSegregationCoefficient(分凝系数):

k0=Cs/ClAlAsBOPSb0.0020.30.80.250.350.023ThevalueofthesegregationcoefficientofsomecommondopantsEffectiveSegregationCoefficientInrealcrystalgrowth,thedopantconcentrationisnotuniforminthemeltedpart.Thereisagradientofconcentration.EffectiveSegregationCoefficientkeisusedtoreplacek0.Visthegrowthspeed.Disthediffusioncoefficientofthedopant.δisthethicknessofthesolid–liquidboundarylayer.ControllingtheUniformityoftheDopingChoosedopantofwhichthek0iscloseto1.IncreasetheboulegrowthrateV.Sothatkeisincreased.Decreasetherotationspeedtoincreasetheboundarythicknessδ.硅、锗晶片易沿{111}面解理，{110)面是第二解理面，常常用于划片。划硅片时应该与硅片解理面平行，也就是与硅片主平边平行或垂直，避免破碎。氧化Thegrowthrateoftheoxidelayer：其中N1是SiO2中氧原子浓度（4.4×1022cm-3

）除以氧源中氧原子数量。（比如以O2为氧源，则除以2,N1,O2=2.2×1022

cm-3

；以H2O为氧源，则除以1,

N1,H2O=4.4×1022

cm-3

）BoundaryCondition：T＝0,thethicknessist0：where：1、Iftheoxidelayerisverythin：2、Whentheoxidelayerisverythick：ControlledbythereactionControlledbythediffusion厚度！时间！B/Aiscalledthelinearreactionrateconstant；Biscalledthequadratic(parabolic)

reactionrateconstant.计算在120分钟内，920℃水汽氧化（640Torr）过程中生长的二氧化硅层的厚度。假定硅片在初始状态时已有1000埃的氧化层。AnalysisontheTemperatureInfluenceForthequadratic

reactionrateconstantB，theinfluenceoftemperatureismainlybasedonitsinfluenceofthediffusionrateD.Becausethediffusionactivationenergyofwaterandoxygenisdifferent,theactivationenergyfordryoxidationandwetoxidationisdifferent.ForthelinearreactionrateconstantB/A，theinfluenceoftemperatureismainlybasedonitsinfluencetoKs.BecausethereactionmechanismofbothwetanddryoxidationareabouttheSi-Sibondbreaking,

theactivationenergyisthesame.Thequadratic

reactionrateconstantBVS.theTemperatureThelinearreactionrateconstantB/A

VSTemperatureInfluenceofoxidationtotheDopants硅的局部氧化（LOCOS）

（localoxidationofsilicon）LOCOSprocessusuallyuseSi3N4asthemaskbecauseitpreventsoxygenandwater.Becauseoftheexpansionoftheoxidelayer,astepofabout0.55toxwillappearandcausetheSiNlayertotilt.Thisiscalledthe“Bird’sBeakeffect(鸟嘴效应)”.Toeliminatethebird’sbeakeffect,siliconinthewindowareashouldbeetchedbeforeoxidation.一块硅样品在1200℃下采用干氧氧化1小时，问：1）生长的氧化层有多厚？2）再在1200℃采用湿氧氧化生长0.1μm需要多长时间？Temp(℃)drywetA(μm)B(μm2/h)τ(h)A(μm)B(μm2/h)8000.370.00119——9200.2350.00491.40.50.20310000.1650.01170.370.2260.28711000.090.0270.0760.110.5112000.040.0450.0270.050.72扩散4.3.1ConstantsourceconcentrationdiffusionzThesolutionoftheFick’ssecondlawis:

4.3.2limitedsourcediffusionBoundaryconditions:ThesolutionisaGaussianDistributionFunction.zCsisafunctionoftime.4.3.3Two-stepdiffusiontechniquePredeposition(预沉积):Constantsourceconcentrationdiffusionatarelativelylowertemperature(800-900oC)forashorttime.

DoseControl2.Drivein(再分布或者主扩散):Limitedsourcediffusionatarelativelyhigherconcentration(1000-1200oC).硅中常用杂质的扩散系数计算方法

施主杂质(负电空位)中性空位受主杂质(正电空位)D02-Ea2-D0-Ea-D0EaD0+Ea+砷(As)

124.050.0663.44

磷(P)444.374.440.93.66

锑(Sb)

154.080.213.65

硼(B)

0.0373.460.413.46注：所有Do的单位都是cm2/s。扩散激活能的单位都是eV。波尔兹曼常数kB=8.617x10-5eV·K−1

空穴带电数！不是指数！硼(B):磷(P):砷(As),锑(Sb):扩散往往需要借助空穴。不同的空穴的带电情况会影响扩散系数。3.3.5杂质相互作用扩散杂质最典型的一个例子就是高浓度发射区扩散时，基区杂质受到发射区杂质的影响，造成内基区和外基区结深之差。根据相互作用的不同，可以分为：发射区推进，发射区收缩发射区推进发射区收缩磷－硼组合（NPN）：发射区推进。高浓度磷扩散时，由P＋V＝离子对离解产生大量的V－型空位，不仅增强了磷在尾区的扩散，还会迁移到较远处，使内基区硼的扩散也增强。砷－硼组合（NPN）：发射区收缩。砷与空位形成稳定的络合物VAs2，使空位欠饱和，造成内基区硼的扩散系数减小。2.IfAsisdiffusedintoathicksliceofSidopedwith1015boronatoms/cm3atatemperatureof1100oCfor3hours,whatisthefinaldistributionofAsifthesurfaceconcentrationisfixedheldat4x1018atoms/cm3?Whatisthejunctiondepth?(Thejuctiondepthcanbeexpressedasanerfc-1(x)function.At1100oC,theintrinsiccarrierdensityofSiisni=1.87x1019atoms/cm3)离子注入离子注入深度离子注入靶中，其射程是一条十分曲折的路径；但在微电子工艺中，所关注的是射程在靶片法线方向上的投影长度，叫投影射程Rp；△Rp则是投影射程的标准偏差，反应了射程的分散宽度，也就是离子主要分布在Rp±△Rp范围内。离子越小，能量越大，射程越远；靶原子量越大，射程越短。硅中常用杂质的投影射程和标准偏差与能量关系注入离子的浓度分布（可用高斯分布来进行模拟）例如可用：标准高斯分布；半高斯分布，但对硼是用皮尔逊（Pearson-Ⅳ）分布。其方法是先假定一个几率分布函数，然后通过实验结果确定函数中的某些参数。这是一种工程方法。在无定形靶中，杂质的浓度分布可以由高斯函数给出：习题

（杂质浓度分布采用高斯分布）一个特殊硅器件需要注入硼，峰值在0.3μm深处，峰值浓度为1017cm-3，求此工艺需要使用的注入能量和剂量。如果衬底材料为N型，衬底浓度为1015cm-3，求注入后的结深。什么叫离子注入中的“沟道效应”，可以采取怎样的措施来减弱“沟道效应”？硅中P型杂质的投影射程和标准偏差与注入能量的关系沟道效应：当注入离子方向平行于主晶轴的时候，会出现沟道效应，沟道内核阻作用很小，电子云密度低，因此离子会沿沟道先进很长距离。不利于控制注入深度！减弱沟道效应的措施：－提高样品温度；－注入方向偏离主晶轴7°－10°；－靶表面淀积非晶层；－预注入，破坏靶表面晶格结构；光刻Photoresist:PositiveorNegative正胶是光照分解！衬底预处理（如脱水、增黏）涂光刻胶预烘曝光增加衬底与光刻胶的黏合性除去光刻胶中的溶剂，使光刻胶的曝光特性固定，90－120℃光源通过掩膜版对光刻胶进行曝光旋转法涂上光刻胶光刻流程显影坚膜曝光后的光刻胶在显影液中进行溶解反应使显影留下的光刻胶进一步硬化，100－180℃左右腐蚀或掺杂等工艺处理去胶进行腐蚀、掺杂、沉积等工艺处理。采用干法或湿法去掉光刻胶。7.3.1传统紫外光学曝光－主要采用紫外光为光源进行曝光，曝光系统包括光源、光学系统、掩膜版和晶片。其曝光方式可以分为：接触式曝光掩膜版与光刻胶紧密接触。优点：曝光对比度高，精度高。缺点：掩膜与光刻胶的接触会造成二者缺陷。接近式曝光掩膜版与光刻胶之间有10－50μm的间距。优点：掩膜和光刻胶之间不接触，缺陷减少。缺点：掩膜和光刻胶之间有缝隙，光的衍射造成分辨率下降。投影式曝光掩膜版与光刻胶之间有投影器（物镜）。优点：高分辨率，低缺陷，对准精度高，曝光图形可缩小。缺点：光学系统较复杂。接近式接触式投影式其中投影式曝光又可分为：扫描式投影曝光和分步重复投影曝光。50Photolithography-ImmersionLithoThemediumbetweenthelensandthewaferbeingexposedneedstohaveanindexofrefraction>1,havelowopticalabsorptionat193nm,becompatiblewithphotoresistandthelensmaterial,beuniformandnon-contaminating.Surprisingly,ultrapurewatermaymeetalloftheserequirements.Waterhasanindexofrefractionn=1.47,absorptionof<5%atworkingdistancesofupto6mm,iscompatiblewithphotoresistandlensandinit’sultrapureformisnon-contaminating.浸没式光刻：在光刻机投影物镜最后一个透镜的下表面与光刻胶之间充满高折射率的液体，从而提高光学分辨率。51Itisknownthatinthesub0.5

mrange,aperfectimageonthemaskcan,fromdiffractioneffect,resultinadistortedpatternintheresist.OPCmaskattempttoreversethesituationbyhavingadistortedimageonthemaskthatisdesignto,produceaperfectimageontheresist.Acomputerisusedtoanalyzeexposureprocessconditions.However,theuseofOPCaresodifficultthattheyareunlikelytobeimplementedonalargescaleinthenearfuture.Resolutionenhancementtechniques:Maskengineering

(1)Opticalproximitycorrections(OPC)5253Resolutionenhancementtechniques:OPC54OpticalProximityCorrection(OPC)canbeusedtocompensatesomewhatfordiffractioneffects.Sharpfeaturesarelostbecausehigherspatialfrequenciesarelostduetodiffraction.Theseeffectscanbecalculatedandcanbecompensatedfor.Thisimprovestheresolutionbydecreasingk1.Photolithography-OPC55Resolutionenhancementtechniques:

(2)OpticalPhaseShiftingDiffractionproblemcouldbemorepronouncedastwomaskpatternsgetclosertogetherOPSusesphaseshiftingto“sharpen”printedimages.Thesetechniquescanallowexistingexposuretoolstobeusedinmanufacturingatleastonemoretechnologygeneration.Unresolvedpattern移相位掩膜技术：相移材料使透射光有180°相移，从而与相邻的透射光发生相消干涉，而不是相长干涉，提高分辨率。56(2)移相位掩膜实现方法：反应等离子体刻蚀调节光程，实现相位反转。镀膜方法1.PhysicalVaporDeposition(PVD)SputteringEvaporatorPulsedLaserDeposition2.ChemicalVaporDeposition(CVD)LPCVDAPCVDPECVDMOCVDAtomicLayerDeposition-ALD3.EpitaxialGrowthMolecularBeamEpitaxy-MBEVaporPhaseEpitaxy-VPESputteringSputteringisatermusedtodescribethemechanisminwhichatomsareejectedfromthesurfaceofamaterialwhenthatsurfaceisstuckbysufficiencyenergeticparticles.Alternativetoevaporation.Firstdiscoveredin1852,anddevelopedasathinfilmdepositiontechniquebyLangmuirin1920.DCsputtering:Metallicfilms:Al-alloys,Ti,TiW,TiN,Tantalum,Nickel,Cobalt,Gold,etc.Thetargetmustbeconducting!!RFsputtering:Almostallkindofinorganiccompounds,metals,metaloxides,metalnitrides,etc.Thetargetcanbeinsulate.MagnetronsputteringHeremagnetsareusedtoincreasethepercentageofelectronsthattakepartinionizationevents,increaseprobabilityofelectronsstrikingAr,increaseelectronpathlength,sotheionizationefficiencyisincreasedsignificantly.Anotherreasonstousemagnets:Lowervoltageneededtostrikeplasma.Controlsuniformity.Reducewaferheatingfromelectronbombardment.Increaseddepositionrate磁控溅射的优点。TargetReactiveGasFilmDepositedAlO2Al2O3AlN2AlNTiO2TiO2TiN2TiNSiN2Si3N4TaO2Ta2O5ZnO2ZnOIn-SnO2In2O3-SnO2ReactiveSputteringRF是射频的意思。RFsputtering是用射频电源来激发等离子，可以轰击绝缘靶，镀各种绝缘材料。CollimatedsputteringOnewaytoimprovethisbyhavinganarrowrangeofarrivalangles,whileatomsarrivingperpendicularlytothewafer.Thismethodcalledcollimatedsputtering(firstproposedin1992).Ahexagonalholesplateisplacedbetweenthetargetandthewafer.CollimatedsputteringAsthesputteredatomstravelthroughthecollimatortowardthewafer,onlythosewithnearlynormalincidencetrajectorywillcontinuetostrikethewafer.Thecollimatorthusactsasaphysicalfiltertolowanglesputteratoms.ComparisonofdifferentPVDMethodsSputterEvaporatorPLDMechanismPlasmaIonbombardThermalEvaporation(FilamentsorE-beam)LaserAblationMaterialDC:MetalRF:AnyMetalAnyAtomEnergy/eV1~100.1~0.55~100Gas0.5~2PaAr,O2,N2<10-4PaAnyOrientationUniformityPoorGoodGoodinVacuumStrainofthefilmMediumLowHighProductionrateHighMediumLowSputterEvaporatorOrCollimatedSputterChemicalVaporDepositionChemicalvapordeposition(CVD)isachemicalprocessusedtoproducehigh-purity,high-performancesolidmaterials.Theprocessisoftenusedinthesemiconductorindustrytoproducethinfilms.InatypicalCVDprocess,thewafer(substrate)isexposedtooneormorevolatileprecursors,whichreactand/ordecomposeonthesubstratesurfacetoproducethedesireddeposit.Frequently,volatileby-productsarealsoproduced,whichareremovedbygasflowthroughthereactionchamber./wiki/Chemical_vapor_depositionCVDUsedinSemicondu