第4章IC工艺之离子注入

第四章：离子注入技术问题的提出：–短沟道的形成？–GaAs等化合物半导体？（低温掺杂）–低表面浓度？–浅结？–纵向均匀分布或可控分布？–大面积均匀掺杂？–高纯或多离子掺杂？要求掌握：–基本工艺流程（原理和工艺控制参数）–选择性掺杂的掩蔽膜（Mask）–质量控制和检测–后退火工艺的目的与方法–沟道效应–在器件工艺中的各种主要应用–离子注入技术的优缺点–剂量和射程在注入工艺中的重要性–离子注入系统的主要子系统–CMOSStructurewithDopedRegionsn-channelTransistorp-channelTransistorLIoxidep–epitaxiallayerp+siliconsubstrateSTISTISTIn+p+p-welln-wellp+p–p+p–p+n+n–n+n–n+ABCEFDGHKLIJMNOn+nn++p+pp++ProcessStepDopantMethodA.p+SiliconSubstrateBDiffusionB.p-EpitaxialLayerBDiffusionC.Retrograden-WellPIonImplantD.Retrogradep-wellBIonImplantE.p-ChannelPunchthroughPIonImplantF.p-ChannelThresholdVoltage(VT)AdjustPIonImplantG.p-ChannelPunchthroughBIonImplantH.p-ChannelVTAdjustBIonImplantI.n-ChannelLightlyDopedDrain(LDD)AsIonImplantJ.n-ChannelSource/Drain(S/D)AsIonImplantK.p-ChannelLDDBF2IonImplantL.p-ChannelS/DBF2IonImplantM.SiliconSiIonImplantN.DopedPolysiliconPorBIonImplantorDiffusionO.DopedSiO2PorBIonImplantorDiffusionIonImplantinProcessFlowImplantDiffusionTest/SortEtchPolishPhotoCompletedwaferUnpatternedwaferWaferstartThinFilmsWaferfabrication(front-end)Hardmask(oxideornitride)AnnealafterimplantPhotoresistmask4.1.离子注入原理4.1.1.物理原理(P.90-98)通过改变高能离子的能量，控制注入离子在靶材料中的位置。a)Lowdopantconcentration(n–,p–)andshallowjunction(xj)MaskMaskSiliconsubstratexjLowenergyLowdoseFastscanspeedBeamscanDopantionsIonimplanterb)Highdopantconcentration(n+,p+)anddeepjunction(xj)BeamscanHighenergyHighdoseSlowscanspeedMaskMaskSiliconsubstratexjIonimplanter–重离子在材料中与靶原子的碰撞是“弹性”库仑散射)((40fEMMMMEtitiT）–级联散射EnergyLossofanImplantedDopantAtomSiSiSiSiSiSiSiSiSiSiSiSiSiSiSiSiSiSiSiSiSiSiSiSiX-raysElectroniccollisionAtomiccollisionDisplacedSiatomEnergeticdopantionSiliconcrystallatticeFigure17.9–能量损失：散射路径R，靶材料密度，阻止本领SEenEEtotpenueltotESESdEESdEdxdEdEERdxdEdxdEdxdE000)()()(()(((）））–能量损失–注入离子的分布N（x）（无电子散射）注入剂量0（atom/cm-2），射程：Rp标准偏差RpScanningdiskwithwafersScanningdirectionFaradaycupSuppressorapertureCurrentintegratorSamplingslitindiskIonbeam–对于无定型材料，–有：为高斯分布–97页图4.82021exp2)(pppRRxRxNtitippMMMMRR32–平均射程pRPage107–多能量、多剂量注入–4.1.2.设备AnalyzingMagnetGraphiteIonsourceAnalyzingmagnetIonbeamExtractionassemblyLighterionsHeavyionsNeutralsFigure17.144.2.沟道效应和卢瑟福背散射6.2.1.沟道效应（page101）沟道峰–沟道效应的消除(临界角）–4.2.2.卢瑟福背散射RBS-C作用？。。。–4.3.注入离子的激活与辐照损伤的消除P.103~1121）注入离子未处于替位位置2）晶格原子被撞离格点Ea为原子的位移阈能atitiTEfEMMMME)((40）大剂量——非晶化临界剂量（P。111）与什么因素有关？如何则量？AnnealingofSiliconCrystalRepairedSilatticestructureandactivateddopant-siliconbondsb)Silatticeafterannealinga)DamagedSilatticeduringimplantIonBeamFigure17.27–热退–P107等时退火IsochronalAnnealing等温退火IsothermalAnnealing/exp()(0tNTtN、)/exp(kTEAe1）激活率(成活率)（%）Si：P、B100%，As50%2）临界通量C(cm-2)F4.16与注入离子种类、大小，能量有关与注入时的衬底温度有关3）退火后的杂质再分布（P。111）4）退火方式：“慢退火”，快速热退火分步退火5）退火完成的指标：电阻率、迁移率、少子寿命–4.4.离子注入工艺中的一些问题1。离子源：汽化高压电离多价问题分子态—原子态问题（产额问题）2。选择性掺杂的掩膜SiO2、Si3N4、光刻胶、各种金属膜•P离子注入SiSiO2Si3N4E(keV)Rp(m)Rp(m)Rp(m)Rp(m)Rp(m)Rp(m)100.0140.0070.0110.0050.0080.004200.0250.0120.0200.0080.0150.006500.0610.0250.0490.0190.0380.0141000.1240.0460.1000.0330.0770.026有掩膜时的注入杂质分布？ControllingDopantConcentrationandDeptha)Lowdopantconcentration(n–,p–)andshallowjunction(xj)MaskMaskSiliconsubstratexjLowenergyLowdoseFastscanspeedBeamscanDopantionsIonimplanterb)Highdopantconcentration(n+,p+)anddeepjunction(xj)BeamscanHighenergyHighdoseSlowscanspeedMaskMaskSiliconsubstratexjIonimplanterFigure17.53。遮挡(注入阴影效应ImplantShadowing)（P119）4.硅片充电Resista)MechanicalscanningwithnotiltIonbeamb)ElectrostaticscanningwithnormaltiltResistElectronShowerforWaferChargingControlAdaptedfromEatonNV10ionimplanter,circa1983++++++++++++++-BiasedapertureElectrongunSecondaryelectrontargetSecondaryelectrons+Ion-electronrecombinationWaferFigure17.23一次电子(几百eV)二次电子(20eV)不能有高能电子!PlasmaFloodtoControlWaferCharging-BiasedapertureIonbeamNeutralizedatomsWaferscandirectionCurrent(dose)monitorPlasmaelectronfloodchamberArgongasinletElectronemissionChamberwall++++++++SNSN+++高能离子注入设计掩蔽膜的形成离子注入退火测试Trim分布、掩蔽膜设计、离子源氧化膜、Si3N4膜、光刻和光刻胶衬底温度、能量、注量温度、时间（多步快速热退火）激活率、残留缺陷、注入层寿命、注入离子再分布（方块电阻、结深）、I-V和C-V特性离子注入工艺流程–4.5.离子注入工艺的应用1。掺杂（P。115）2。浅结形成（ShallowJunctionFormation,p116)3。埋层介质膜的形成(page116)如：注氧隔离工艺（SIMOX）（SeparationbyImplantedOxygen)4。吸杂工艺如：等离子体注入（PIII）吸杂工艺（PlasmaImmersionIonImplantation）5。SmartCutforSOI6。聚焦离子束技术7。其它（如：离子束表面处理）BuriedImplantedLayern-wellp-wellpEpilayerp+Siliconsubstratep+BuriedlayerRetrogradewells埋层注入，替代埋层扩散和外延控制闩锁效应RetrogradeWelln-wellp-wellp+Buriedlayerp+Siliconsubstraten-typedopantp-typedopantp++n++倒置井：闩锁效应和穿通能力PunchthroughStopn-wellp-wellp+Buriedlayerp+Siliconsubstraten-typedopantp-typedopantp+p++n+n++穿通阻挡ImplantforThresholdVoltageAdjustmentn-wellp-wellp+Buriedlayerp+Siliconsubstraten-typedopantp-typedopantp+p++pn+n++n阈值电压调整Source-DrainFormations++++++++----------++++++++++++++++----------------n-wellp-wellp+Buriedlayerp+Siliconsubstratep+S/Dimplantn+S/DimplantSpaceroxideDrainSourceDrainSourceb)p+andn+Source/drainimplants(performedintwoseparateoperations)++++++++----------n-wellp-wellp+Buriedlayerp+Siliconsubstratep-channeltransistorp–LDDimplantn-channeltransistorn–LDD