光电半导体材料科学与技术ppt课件

.,电子束通过5-10kV的电场加速后，聚焦并打到待蒸发材料表面，电子束将能量传递给待蒸发材料使其熔化，电子束迅速损失能量。电子束蒸发系统的核心部件：电子束枪（热阴极和等离子体电子）电子束聚焦方式：静电聚焦和磁偏转聚焦电子束产生后，需要对其进行聚焦而能够直接打到被蒸发材料的表面。,.,电子束蒸发源的优点电子束轰击热源的束流密度高，能获得远比电阻加热源更大的能量密度。达到104109W/cm2的功率密度，可用于蒸发高熔点材料，如W、Mo等。被蒸发材料可置于水冷坩锅中避免容器材料蒸发、及其与蒸发材料反应热量可直接加到蒸镀材料的表面热效率高、热传导和热辐射损失小电子束蒸发源的缺点电子枪发出的一次电子和蒸发材料发出的二次电子会使蒸发原子和残余气体分子电离影响膜层质量。可选择电子枪加以解决电子束蒸镀装置结构复杂、价格昂贵加速电压高时，产生辐射伤害,.,直流溅射(导电靶材)射频溅射(绝缘介质靶材)反应溅射(氧化物、氮化物靶材),磁控溅射系统,.,溅射的基本原理:物质的溅射现象溅射：荷能粒子与固体（靶材）表面相互作用过程中，发生能量和动量的转移，当表面原子获得足够大的动能而脱离固体表面，从而产生表面原子的溅射。溅射参数溅射阀值：将靶材原子溅射出来所需的入射离子最小能量值。与入射离子的种类关系不大、与靶材有关。溅射产额溅射离子速度和能量,.,5,溅射物理过程,.,6,入射离子轰击靶材时，平均每个正离子能从靶材打出的原子数为溅射产额（）。M1、M2:分别为入射离子和靶材原子的质量；U0:靶材表面束缚能，eV;E:入射离子的能量，eV:无量纲参数,.,溅射物理机制,Underlowenergeticionbombardment(singleknock-On)LinearcollisioncascadeUnderhighenergeticionbombardment(spike),.,DCSputtering,Processpressure-compromisebetweenthenumberofArionsandthescatteringofArionswithneutralAratomsSputtervoltage-maximumyield,typical-2-5kVSubstratebias-controlionbombardmentcharacteristicsSubstratetemperature-modifydepositedfilmproperties,.,RFSputtering,Forinsulatingmaterialsduetopositivechargebuildsuponthecathode(target)inDCsystems.Alternatingpotentialcanavoidchargebuildup.Whenfrequencieslessthanabout50kHz,electronsandionsinplasmaaremobileWhenfrequenciesaboveabout50kHz,ions(heavy)cannolongerfollowtheswitching-electronscanneutralizepositivechargebuildup,.,MagnetronSputtering,I.MagnetronConfiguration:planar,NdFeBbarmagnetwithamagneticfieldof0.5GonthetargetfrontsurfaceElectronmotionisconfinedtoaracetrackduetodriftingbyEandBperpendiculartoeachother.,.,11,.,12,化学气相沉积ChemicalVaporTransport,GasmeasurementandmonitoringTransportofmoleculesbygasflowanddiffusionTransportofheatbyconvection,conduction,andradiationChemicalreactionsinthegasphaseandatthesurfaces,.,化学气相沉积分类,常压CVD（APCVD）,低压CVD（LPCVD）,等离子增强CVD（PECVD）,.,.,CVD薄膜生长过程,气体源进入反应器；源材料扩散至表面；源材料吸附在表面；产生化学反应；生成物形成晶核；晶核形成岛状物；形成连续薄膜；气体副产物排出,.,Masstransportdependson,CVD生长过程中的质量输运,两种传输模式：分子流传输（气体扩散）粘滞流传输(反应物传输至衬底表面进行反应),.,CVD薄膜的主要性能参数,.,.,等离子体增强CVD在射频功率条件下，反应气体从等离子中获得激活能，被激活并增强化学反应，实现高效率的化学气相沉积等离子轰击能够去除表面杂质，增加薄膜的附着性反应温度低于其它CVD薄膜沉积方法,.,20,等离子体基本物理性质,等离子中包括相同数目的离子和电子，呈现电中性。用于刻蚀的等离子体中带电粒子密度109-1012个/cm-3。等离子中电子温度104K,刻蚀过程中与室温中性气体分子生成活化自由基，与衬底材料结合生成挥发气体产物，从而刻蚀衬底。,.,Application:maskstopreventoxidationforLOCOSprocessfinalpassivationbarrierformoistureandsodiumcontaminationPECVDLPCVD,沉积氮化硅,.,原子层沉积技术(AtomicLayerDeposition),ALDisamethodofapplyingthinfilmstovarioussubstrateswithatomicscaleprecision.Similarinchemistrytochemicalvapordeposition(CVD),exceptthattheALDreactionbreakstheCVDreactionintotwohalf-reactions,keepingtheprecursormaterialsseparateduringthereaction.ALDfilmgrowthisself-limitedandbasedonsurfacereactions,whichmakesachievingatomicscaledepositioncontrolpossible.Bykeepingtheprecursorsseparatethroughoutthecoatingprocess,atomiclayerthicknesscontroloffilmgrowncanbeobtainedasfineasatomic/molecularscalepermonolayer.,.,原子层沉积过程与设备,Releasessequentialprecursorgaspulsestodepositafilmonelayeratatimeonthesubstrate.Theprecursorgasisintroducedintotheprocesschamberandproducesamonolayerofgasonthewafersurface.Asecondprecursorofgasisthenintroducedintothechamberreactingwiththefirstprecursortoproduceamonolayeroffilmonthewafersurface.3.Twofundamentalmechanisms:ChemisorptionsaturationprocessSequentialsurfacechemicalreactionprocess4.Sinceeachpairofgaspulses(onecycle)producesexactlyonemonolayeroffilm,thethicknessoftheresultingfilmmaybepreciselycontrolledbythenumberofdepositioncycles.,.,Example:ALDcycleforAl2O3deposition,Step1,.,Step2,.,Step3,.,Step4,.,Step5,.,Step6,.,After3cycles,.,Eachpairofgaspulses(onecycle)producesexactlyonemonolayeroffilm,thethicknessoftheresultingfilmmaybepreciselycontrolledbythenumberofdepositioncycles.,.,MaintypesofALDreactorsClosedsystemchambers(mostcommon)Thereactionchamberwallsaredesignedtoeffectthetransportoftheprecursors.,Ref:TechnologyBackgrounder:AtomicLayerDeposition,ICKnowledgeLLC,24April06.,.,ProcessTemperature1,1,1,1TechnologyBackgrounder:AtomicLayerDeposition,ICKnowledgeLLC,24April06.,.,CandidatesforHigh-KdielectricsFilmPrecursorsAl2O3Al(CH)3,H2OorO3HfO2HfCl4orTEMAH,H2OZrO2ZrCl4,H2O,ALDApplications,High-KdielectricsforCMOS,ReducesleakagecurrentFasterswitchingspeedCoolertransistors,Ref:IntelsHigh-k/MetalGateAnnouncement,IntelCorporation.26April,06.,Semiconductormemory(DRAM)CuinterconnectbarrierDepositioninporousstructures,.,AdvantagesStoichiometricfilmswithlargeareauniformityand3Dcon