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1、第六章扫描电子显微术第1页，本讲稿共46页Lettuce Field(16M DRAM)Theory of Scanning Electron MicroscopeHitachi High-Technologies CorporationHitachi High-Technologies CorporationNano Technologies Sales Dept.Nano Technologies Sales Dept.第2页，本讲稿共46页1.Resolution Improvement30kV1kV0.6 nm0.6 nm0.5 nm2.5 nm3.5 nm1.8 nmS-5200S-
2、5000HS-5000Development of a new UHR Obj.Lens第3页，本讲稿共46页第4页，本讲稿共46页New S-4800 FE-SEM New S-4800 FE-SEM Resolution:1.0nm 15kV1.4nm 1kV第5页，本讲稿共46页Configuration of a scanning electron microscopeConfiguration of a scanning electron microscopeObjective Movable ApertureModel S-3000NSpecimen StageCRTElectro
3、n GunSE DetectorSpecimen Chamber第6页，本讲稿共46页Comparison among OM,TEM and SEMComparison among OM,TEM and SEM第7页，本讲稿共46页第一节结构原理扫描电镜基本上是由电子光学系统、信号接收系统、供电系统、真空系统等四部分组成。在扫描电镜中，电子枪发射出来的电子束，经三个电磁透镜聚焦后，成直径20微米25的电子束。置于末级透镜上部的扫描线圈能使电子束在试样表面上做光栅状扫描。试样在电子束作用下，激发出各种信号，信号的强度取决于试样表面的形貌、受激区域的成分和晶体取向。值得强调的是，入射电子束在试样表
4、面上是逐点扫描的，像是逐点记录的，因此试样各点所激发出来的各种信号都可记录下来。给试样的综合分析带来极大的方便。第8页，本讲稿共46页SE DetectorSpecimenCRTCameraAmplifierImage SignalHigh VoltageDeflection CoilsDeflection AmplifierVacuum PumpFilamentWehneltElectron GunAnodeCondenser LensDeflection CoilsObjective LensSpecimen ChamberScanning Electron BeamMag.Control
5、Configuration of a scanning electron microscopeConfiguration of a scanning electron microscope第9页，本讲稿共46页PG1PG2FilamentCondenser Lens apertureOrificeNVVacuumGaugeVacuum controller (Real-time)Vacuumcondition presetRP1RP2DPLow VacuumConditionBSE detectorV8V6V9V3V4V1SpecimenV5V7High VacuumConditionV2Bl
6、ock diagram of evacuating systemBlock diagram of evacuating system第10页，本讲稿共46页ImageSampleObjective Lens(Illumination Source)LumpO MCondenser LensProjection LensScreenImageImageSampleSampleObjective LensElectron SourceCondenser LensDeflection CoilsSE DetectorC R TT E MS E MFluorescent screenScanningD
7、ifference among OM,TEM and SEMDifference among OM,TEM and SEM第11页，本讲稿共46页FE TipTungsten Filament750mElectron SourceType of EmissionOperating Vacum(Pa)Brightness(A/cm2 str)Source Size(m)Energy Spred(eV)Life Time(h)Tungsten FilamentThermonicField EmissionCold FE10-510-85x105108300.012.00.2502000第12页，本
8、讲稿共46页Energy SpreadEnergy SpreadEffect of chromatic aberration Effect of chromatic aberration V=2eVTungsten FilamentCrossover ofCrossover of Low EnergyLow EnergyElectronsElectronsCrossover of Crossover of High EnergyHigh EnergyElectronsElectronsV=0.2eVFE TipCrossover ofCrossover of Low EnergyLow Ene
9、rgyElectronsElectronsCrossover ofCrossover of High EnergyHigh EnergyElectronsElectrons第13页，本讲稿共46页WehneltAnodeElectron BeamV0Electron BeamV01st Anode2nd AnodeFlashing VoltageV1V0:Accelerating voltageV1:Extraction voltageBias Voltage Control Thermionic EmissionThermionic EmissionCold Field EmissionCo
10、ld Field Emission(6.5kV)Filament Current ControlFilamentComparison of electron gunsComparison of electron guns第14页，本讲稿共46页In-LensType(S-5200)In-LensType(S-5200)PrimaryBeamPrimaryBeamLensSEDetectorSEDetectorSpecimenSpecimenTheory of Scanning Electron MicroscopeTheory of Scanning Electron Microscope第1
11、5页，本讲稿共46页OutLensType(W-SEM,S-4300)OutLensType(W-SEM,S-4300)PrimaryBeamPrimaryBeamLensSpecimenSE Detector第16页，本讲稿共46页SnorkelType(S-4700&S-4800)SnorkelType(S-4700&S-4800)SEDetectorSEDetector(Upper)(Upper)SpecimenLensLensPrimarybeamPrimarybeamSEdetectorSEdetector(Lower)(Lower)第17页，本讲稿共46页The illuminat
12、ion angle(The illumination angle()of a scanning electron microscope)of a scanning electron microscopeFocal LengthObjective LensObjective Movable ApertureSpecimenWorking DistanceElectron SourceElectron Beam第18页，本讲稿共46页LensLensPrimarybeamPrimarybeamUpperHigh ResolutionLowerTopographic ImageNon Conduct
13、ive SamplesSelectUpperandSelectUpperandLowerDetectorsLowerDetectors第19页，本讲稿共46页PrimarybeamLensSEDetectorSpecimen)In-lens typePrimarybeamSEDetectorLensSpecimen)Conventional type(Out-Lens)SEDetector(Upper)SpecimenLensPrimarybeam)Snokel typeSEDetector(Lower)Hi-SEMS-4300S-4700S-5200第20页，本讲稿共46页Primary E
14、lectron Beam Reducing charge-up with Natural-SEMReducing charge-up with Natural-SEM eeObjective LensBSE DetectorResidual GasHigh Pressure (1.0Pa270Pa）Non ConductiveSpecimen第21页，本讲稿共46页Astigmatism correction methodAstigmatism correction methodBeam DiameterBefore correctionObjective LensElectron Sourc
15、eElectron BeamXYElectron BeamElectron SourceObjective LensStigmatorAfter correctionYXStigmatorBeam Diameter第22页，本讲稿共46页PhotomultiplierPrimary Electron BeamSpecimenPhotonsLight GuideSignalCRT+10kVSecondary ElectronScintillatorScintillatorPhosphorsAl Coating LayerSecondary electron detection systemSec
16、ondary electron detection systemPhoto Multiplier Tube第23页，本讲稿共46页第二节分辨率和放大倍数一、分辨率扫描电镜的分辨率有两重意义：对微区成分而言，它是指能分析的最小区域；对成像而言，它是指能分辨两点之间的最小距离。这两者主要决定入射电子束的直径，但并不直接等于直径。二是由所接收信号的激发区域半径决定。二、放大倍数扫描电镜的放大倍率M取决于显像管荧光屏尺寸S2和入射束在试样表面扫描距离S1之比，即第24页，本讲稿共46页三、入射电子在试样内的激发区域入射电子在被散射或吸收之前，将在试样表面下的某个距离R范围内运动，并激发各种射线。这些射
17、线的能量或穿透能力各不相同，只有一定深度一定能量的射线才能逸出表面，被检测到。对于一般元素而言，电子束与试样作用，激发区域是一个梨形作用区。对重金属而言，此激发区域是一个半球形区域。不同的信号来自此激发区内不同的深度。第25页，本讲稿共46页BackscatteredBackscatteredElectronElectronSecondaryElectronSecondaryElectronSample(Metal)Sample(Metal)Sample(Metal)Sample(Metal)VaccumVaccumSimons,et.alSimons,et.al第26页，本讲稿共46页 SE
18、Primary Electron BeamBSESpecimen特征X射线荧光X射线俄歇电子dZBZXZFRBRXRF各种信号发生的深度（Z）和广度（R）第27页，本讲稿共46页Secondary ElectronsCarrying Surface Information Of Specimen一 一一一一一一一一一一一一一一ZExcitation Depthfor SecondaryElectron Emission一一一Secondary ElectronsSESESecondary ElectronsCarrying Inner InformationOf SpecimenPrimary
19、 Electron BeamBSEBackscatteredElectronsSpecimen SE and BSE emitted from solid sample SE and BSE emitted from solid sample 第28页，本讲稿共46页1kV2kV3kV1020304050(nm)BeamInvadingdepthTheory of Scanning Electron MicroscopeTheory of Scanning Electron Microscope第29页，本讲稿共46页Primary Electron BeamSecondary Electro
20、nBackscattered ElectronCathodeluminescenceSpecimen CurrentTransmitted ElectronElectron Beam Induced CurrentSecondary Electron Detector10nm(Excitation Volume for Secondary Electron Emission)Transmitted Electron (Scattered)Characteristic X-RayThe primary electron beam-specimen The primary electron bea
21、m-specimen interaction in the SEM interaction in the SEM 第30页，本讲稿共46页第三节 电子束与试样相互作用激发的各种信号及工作方式一、发射方式-二次电子 二次电子能量大致在030eV之间，多数来自表面层下部550深度之间。二次电子信号对试样表面状态非常敏感。二、反射方式-被反射电子 能量与入射电子能量相当，来自表面层几个微米的深度范围。被反射电子信号可以显示表面形貌，还可以显示元素分布。三、吸收方式-吸收电子 吸收电子成像衬度与二次电子、被反射电子像衬度相反，可以显示元素分布和表面形貌，尤其是裂缝内部微观形貌。第31页，本讲稿共46页
22、四、透射方式-透射电子 透射电子中既有弹性散射电子也有非弹性散射电子。其能量大小取决于试样的性质和厚度。可以显示成分分布。五、俄歇电子方式-俄歇电子 能量极低，具有元素的特征能量，适合于做表层成分分析。六、X射线方式-特征X射线 高能入射电子轰击固体试样，就好像一只X射线管，试样是其中的靶。特征X射线的波长因试样元素不同而不同，其相对强度与元素含量有关。七、阴极发光方式-可见光 有些物质在高能电子束轰击下会发光，发光波长与杂质原子和基体物质有关。对发光光谱做波长分析，可以鉴别出基体第32页，本讲稿共46页物质和所含的杂质。用光电倍增管接收、成像就可以显示杂质及晶体缺陷分布情况。八、感应信号方式
23、-感应电信号 半导体和绝缘体在高速电子束的轰击下会在其中产生空穴-电子对，感应信号就是以此作信号的一种工作方式。这种方式可以显示半导体、绝缘体的表面形貌、晶体缺陷、微等离子体和p-n结。第33页，本讲稿共46页10010,0001Energy of Electron (eV)Quantity of Electrons(Incident beam energy:10,000eV)Energy spectrum of the electrons emitted from a specimen Energy spectrum of the electrons emitted from a speci
24、men Secondary ElectronsBackscattered Electrons第34页，本讲稿共46页Scanning(Y)Scanning(X)lScanning Electron ProbeSEMSEMSEMSEMSpecimenScanning Electron Beam of CRTLPixelC R TMagnification:(M)=L/lMagnifying mechanism in the SEMMagnifying mechanism in the SEM第35页，本讲稿共46页第36页，本讲稿共46页第四节 形貌象解释二次电子产额强烈依赖于入射束与试样表面法
25、线间的夹角，也就是说，如果试样表面是凸凹不平的话，法线与入射束夹角大的面发射的二次电子多，反之则少。其二是二次电子的实际收得率是呈角分布的。探测器愈是垂直于试样表面，所收集到的二次电子数也就愈多。(a)=050Rr1(b)=4550Rr250Rr3(c)=65r3r2r1入射电子在试样表层下50深度内所经路程随面法线间夹角的变化 第37页，本讲稿共46页9090603003060试样02040 60 80246810接收的二次电子二次电子收得数角分布曲线二次电子收得数与入射束-试样面法线间夹角分布曲线第38页，本讲稿共46页 Theory of Theory of ScanningScanni
26、ng Electron Microscope Electron MicroscopeComparison of objective movable aperture hole sizeComparison of objective movable aperture hole sizeFocus DepthDeepFocus DepthShallowAperture Size:SmallAperture Size:SmallAperture Size:LargeAperture Size:LargeSpecimen:Si on Photo Resist Pattern第39页，本讲稿共46页Th
27、eory of Scanning Electron MicroscopeTheory of Scanning Electron MicroscopeAfter correctionBefore correctionUnder focusUnder focusJust focusJust focusOver focusOver focusJust focusJust focusAstigmatism correction methodAstigmatism correction methodSpecimen:Trachea of rat第40页，本讲稿共46页Theory of Scanning
28、 Electron MicroscopeTheory of Scanning Electron MicroscopeW filament SEMOut lens FE-SEMSnorkel lens FE-SEMIn-Lens FE-SEM0.5 1.0 10 300.51.01020Acc.(kV)Resolution(nm)Comparison of resolutionComparison of resolution第41页，本讲稿共46页 Comparison of high and low acclerating voltageComparison of high and low a
29、cclerating voltageTheory of Scanning Electron MicroscopeTheory of Scanning Electron MicroscopeHigh Acclerating Voltage Low Acclerating VoltageVacc:15kVVacc:1.0kVSpecimen:Solar Battery第42页，本讲稿共46页Charge-up PhenomenaEliminate Charge-up PhenomenaVacc:1.5kVVacc:1.5kVVacc:0.7kVVacc:0.7kVSpecimen:SiO2 on
30、Photo Resist Line PatternObservation at lower accelerating voltagesObservation at lower accelerating voltages第43页，本讲稿共46页Non-Conductive SamplesObservationSpecimen:CeramicsVacc:1kVUpper DetectorVacc:1kVLower Detector第44页，本讲稿共46页第五节 晶体学分析一、通道花样形成原理电子通道花样是一种相当弱的衍衬效应。结合中这种效应需要用电子衍射动力学理论。二、通道花样性质每个(hkl)通
31、道带都平行于相应的(hkl)晶面积线；通道带的宽度W于2成反比，从而可知与加速电压的1/2次方成反比；如果几个通道带的中心线相交于一点，则这几个通道带同属于一个晶带，交点就是此晶带的晶带轴的迹。如果晶带轴的迹和投影轴的迹重合，则属于此晶带的任何两通带间夹角即等于相应的两个晶面间的夹角。如果晶带轴的迹和投影轴的迹不重合，则表明两轴间第45页，本讲稿共46页成一倾角，可以证明，两晶面间夹角0与以及图(a)所示的1、2之间有如下关系：三、实验方法只要采用适当的扫描方式，使入射束相对于晶体表面法线的扫描角连续改变就有可能得到通道花样。MP12图(a)两晶面的晶带轴和投影轴不重合时，晶面夹角和其他有关夹角关系第46页，本讲稿共46页