Table Of ContentEdited by
Gang He and Zhaoqi Sun
High-k Gate Dielectrics for CMOS
Technology
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Edited by Gang He and Zhaoqi Sun
High-k Gate Dielectrics for CMOS
Technology
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V
Contents
Preface XV
List of Contributors XVII
Color Plates XXIII
PartOne ScalingandChallengeofSi-basedCMOS 1
1 ScalingandLimitationofSi-basedCMOS 3
GangHe,ZhaoqiSun,MaoLiu,andLideZhang
1.1 Introduction 3
1.2 ScalingandLimitationofCMOS 4
1.2.1 DeviceScalingandPowerDissipation 4
1.2.2 GateOxideTunneling 7
1.2.3 GateOxideScalingTrends 8
1.2.4 ScalingandLimitationofSiO GateDielectrics 10
2
1.2.5 SiliconOxynitrides 14
1.3 TowardAlternativeGateStacksTechnology 16
1.3.1 AdvancesandChallengesinDielectricDevelopment 16
1.3.2 AdvancesandChallengesinElectrodeDevelopment 19
1.4 ImprovementsandAlternativetoCMOSTechnologies 22
1.4.1 ImprovementtoCMOS 22
1.4.1.1 NewMaterials 22
1.4.1.2 NewStructures 23
1.5 PotentialTechnologiesBeyondCMOS 23
1.6 Conclusions 24
References 25
PartTwo High-kDepositionandMaterialsCharacterization 31
2 IssuesinHigh-kGateDielectricsanditsStackInterfaces 33
Hong-LiangLuandDavidWeiZhang
2.1 Introduction 33
2.2 High-kDielectrics 33
2.2.1 TheCriteriaRequiredforHigh-kDielectrics 34
VI Contents
2.2.2 TheChallengesofHigh-kDielectrics 37
2.2.2.1 StructuralDefects 37
2.2.2.2 ChannelMobilityDegradation 38
2.2.2.3 ThresholdVoltageControl 38
2.2.2.4 Reliability 39
2.3 MetalGates 40
2.3.1 BasicRequirementsforMetalGates 41
2.3.2 MetalGateMaterials 41
2.3.2.1 PureMetals 42
2.3.2.2 MetallicAlloys 42
2.3.2.3 MetalNitrides 42
2.3.2.4 MetalSilicides 43
2.3.3 WorkFunction 43
2.3.4 MetalGateStructures 44
2.3.5 MetalGate/High-kIntegration 44
2.3.6 ProcessIntegration 44
2.4 IntegrationofHigh-kGateDielectricswithAlternative
ChannelMaterials 45
2.4.1 High-k/GeInterface 46
2.4.2 High-k/III–VInterface 49
2.5 Summary 51
References 52
3 UVEngineeringofHigh-kThinFilms 61
IanW.Boyd
3.1 Introduction 61
3.2 GasDischargeGenerationofUV(Excimer)Radiation 61
3.3 ExcimerLampSourcesBasedonSilentDischarges 63
3.4 PredepositionSurfaceCleaningforHigh-kLayers 65
3.5 UVPhotonDepositionofTa O Films 66
2 5
3.6 PhotoinducedDepositionofHf1(cid:2)xSixOyLayers 70
3.7 Summary 73
References 73
4 AtomicLayerDepositionProcessofHf-BasedHigh-kGate
DielectricFilmonSiSubstrate 77
TaeJooPark,MoonjuCho,Hyung-SukJung,andCheolSeongHwang
4.1 Introduction 77
4.2 PrecursorEffectontheHfO Characteristics 78
2
4.2.1 HafniumPrecursorEffectontheHfO DielectricCharacteristics 78
2
4.2.1.1 HafniumChloride(HfCl ) 78
4
4.2.1.2 TetrakisDimethylamidoHafnium[HfN(CH ) ] 82
324
4.2.1.3 TetrakisEthylmethylaminoHafnium(Hf[N(C H )(CH )] ) 85
2 5 3 4
4.2.1.4 tert-Butoxytris[Ethylmethylamido]Hafnium(HfOtBu[NEtMe] ) 86
3
4.2.1.5 tert-ButoxideHafnium(Hf[OC H ] ) 87
4 94
Contents VII
4.2.2 OxygenSourcesandReactants 88
4.2.2.1 H OversusO 88
2 3
4.2.2.2 O Concentration 93
3
4.2.2.3 ReactantsforInSituNIncorporation 95
4.3 DopedandMixedHigh-k 97
4.3.1 Zr-DopedHfO 98
2
4.3.2 Si-DopedHfO 100
2
4.3.3 Al-DopedHfO 102
2
4.4 Summary 105
References 105
5 StructuralandElectricalCharacteristicsofAlternative
High-kDielectricsforCMOSApplications 111
Fu-ChienChiu,SomnathMondal,andTung-MingPan
5.1 Introduction 111
5.2 RequirementofHigh-kOxideMaterials 114
5.3 Rare-EarthOxideasAlternativeGateDielectrics 117
5.4 StructuralCharacteristicsofHigh-kREOxide
Films 118
5.4.1 ProcessCompatibility 118
5.4.2 X-RayDiffractionAnalysis 120
5.4.3 AtomicForceMicroscopeInvestigation 122
5.4.4 TransmissionElectronMicroscopyTechnique 125
5.4.5 X-RayPhotoelectronSpectroscopyAnalysis 128
5.5 ElectricalCharacteristicsofHigh-kREOxideFilms 132
5.5.1 TheThresholdVoltage,FlatbandVoltage,InterfaceTrap,
andFixedCharge 132
5.5.2 LeakageMechanism 134
5.5.2.1 SchottkyorThermionicEmission 135
5.5.2.2 Fowler–NordheimTunneling 137
5.5.2.3 DirectTunneling 139
5.5.2.4 ThermionicFieldEmission 141
5.5.2.5 Poole–FrenkelEmission 141
5.5.2.6 HoppingConduction 142
5.5.2.7 OhmicConduction 144
5.5.2.8 SpaceCharge-LimitedConduction 145
5.5.2.9 IonicConduction 149
5.5.2.10 GrainBoundary-LimitedConduction 149
5.5.3 High-kSiliconInterface 150
5.5.4 BandAlignment 153
5.5.5 ChannelMobility 163
5.5.6 DielectricBreakdown 166
5.6 ConclusionsandPerspectives 171
References 172
VIII Contents
6 HygroscopicToleranceandPermittivityEnhancementofLanthanum
Oxide(La O )forHigh-kGateInsulators 185
2 3
YiZhao
6.1 Introduction 185
6.2 HygroscopicPhenomenonofLa O Films 186
2 3
6.2.1 EffectofMoistureAbsorptiononSurfaceRoughnessofLa O
2 3
Films 187
6.2.2 EffectofMoistureAbsorptiononElectricalPropertiesofLa O
2 3
Films 188
6.3 LowPermittivityPhenomenonofLa O Films 191
2 3
6.3.1 MoistureAbsorption-InducedPermittivityDegradationofLa O
2 3
Films 191
6.3.2 PermittivityofLa O FilmswithoutMoistureAbsorption 193
2 3
6.4 HygroscopicToleranceEnhancementofLa O Films 194
2 3
6.4.1 HygroscopicToleranceEnhancementofLa O FilmsbyY O
2 3 2 3
Doping 194
6.5 HygroscopicToleranceEnhancementofLa O Films
2 3
byUltravioletOzoneTreatment 198
6.6 ThermodynamicAnalysisofMoistureAbsorption
PhenomenoninHigh-kGateDielectrics 203
6.7 PermittivityEnhancementofLa O FilmsbyPhaseControl 205
2 3
6.7.1 ExperimentalProceduresandCharacterizations 207
6.7.2 PermittivityEnhancementbyPhaseControlduetoY O Doping 208
2 3
6.7.3 Higher-kAmorphousLa TaO Films 213
1-x x y
6.8 Summary 219
References 221
7 CharacterizationofHigh-kDielectricInternalStructureby
X-RaySpectroscopyandReflectometry:NewApproachestoInterlayer
IdentificationandAnalysis 225
ElenaO.Filatova,AndreyA.Sokolov,andIgorV.Kozhevnikov
7.1 Introduction 225
7.2 ChemicalBondingandCrystallineStructureofTransition
MetalDielectrics 227
7.3 NEXAFSInvestigationofInternalStructure 229
7.4 StudyingtheInternalStructureofHigh-KDielectricFilmsby
HardX-RayPhotoelectronSpectroscopyandTEM 236
7.5 StudyingtheInternalStructureofHigh-KDielectricFilms
byX-rayReflectometry 244
7.5.1 ReconstructionoftheDielectricConstantProfilebyHardX-Ray
Reflectometry 244
7.5.2 ReconstructionoftheDepthDistributionofChemicalElements
ConcentrationbySoftX-RayReflectometry 254
References 266
Contents IX
8 High-kInsulatingFilmsonSemiconductorsandMetals:General
TrendsinElectronBandAlignment 273
ValeriV.Afanasev,MichelHoussa,andAndreStesmans
8.1 Introduction 273
8.2 BandOffsetsandIPESpectroscopy 274
8.3 Silicon/InsulatorBandOffsets 277
8.4 BandAlignmentatInterfacesofHigh-Mobility
Semiconductors 280
8.5 Metal/InsulatorBarriers 284
8.6 Conclusions 289
References 289
PartThree ChallengeinInterfaceEngineeringandElectrode 293
9 InterfaceEngineeringintheHigh-kDielectricGateStacks 295
ShijieWang,YuanpingFeng,andAlfredC.H.Huan
9.1 Introduction 295
9.2 High-kOxide/SiInterfaces 295
9.2.1 GrowthofCrystallineHigh-kOxideonSemiconductors 297
9.2.2 MeasurementofBandAlignmentatHigh-kOxide/SiInterfaces 298
9.3 MetalGate/High-kDielectricInterfaces 303
9.4 ChemicalTuningofBandAlignmentsforMetalGate/High-k
OxideInterfaces 308
9.5 SummaryandDiscussion 314
References 315
10 InterfacialDipoleEffectsonHigh-kGateStacks 319
LiQiangZhu
10.1 Introduction 319
10.2 MetalGateConsideration 321
10.3 InterfacialDipoleEffectsinHigh-kGateStacks 324
10.3.1 ModificationoftheGateWorkFunctionbytheInterfacialDipole 324
10.3.2 Fermi-LevelPinningEffectsatGate/High-kInterfaces 326
10.3.3 MicromodelsfortheInterfacialDipoleinHigh-kStacks 328
10.3.3.1 Fermi-LevelPinning 328
10.3.3.2 OxygenVacancyModel 329
10.3.3.3 PaulingElectronegativityModel 330
10.3.3.4 AreaOxygenDensityModel 331
10.4 ObservationoftheInterfacialDipoleinHigh-kStacks 332
10.4.1 FlatbandVoltageShiftsinCapacitance–VoltageMeasurements 333
10.4.2 Core-LevelBindingEnergyShiftinPhotoelectron
Spectroscopy 335
10.4.2.1 BandDiscontinuitiesandSchottkyBarrierAnalysisin
Heterostructures 336
10.4.2.2 InterfacialChargeInvestigation 337
X Contents
10.4.2.3 BandAlignmentDetermination 337
10.4.2.4 InterfacialDipoleMeasurementbyPhotoelectronSpectroscopy 339
10.4.3 BandAlignmentsMeasuredbyUsingInternalPhotoemission 345
10.4.4 PotentialShiftsinKelvinProbeMeasurements 346
10.5 Summary 348
References 349
11 MetalGateElectrodeforAdvancedCMOSApplication 355
WenwuWang,XiaoleiWang,andKaiHan
11.1 TheScalingandImprovedPerformanceofMOSFETDevices 355
11.2 UrgentIssuesaboutMOSGateMaterialsforSub-0.1mm
DeviceGateStack 360
11.2.1 SiO GateDielectric 360
2
11.2.2 PolysiliconElectrode 363
11.3 NewRequirementsofMOSGateMaterialsforSub-0.1mm
DeviceGateStack 365
11.3.1 High-kGateDielectric 365
11.3.2 MetalGateElectrode 367
11.4 Summary 374
References 374
PartFour Developmentinnon-Si-basedCMOStechnology 379
12 MetalGate/High-kCMOSEvolutionfromSitoGePlatform 381
AlbertAchin
12.1 Introduction 381
12.2 High-k/SiCMOSFETs 386
12.2.1 PotentialInterfaceReactionMechanism 387
12.2.2 InsertinganUltrathinSiON 388
12.2.3 Low-TemperatureProcess 389
12.3 High-k/GeCMOSFETs 392
12.3.1 Defect-FreeGe-on-Insulator 392
12.3.2 TheChallengeforGen-MOS 394
12.3.3 High-MobilityGen-MOSUsingNovelTechnology 395
12.4 GePlatform 397
12.4.1 LogicandMemoryIntegration 397
12.4.2 3DGeOI/SiIC 400
12.5 Conclusions 401
References 402
13 TheoreticalProgressonGaAs(001)SurfaceandGaAs/high-kInterface 407
WeichaoWang,KaXiong,RobertM.Wallace,andKyeongjaeCho
13.1 Introduction 407
13.2 ComputationalMethod 409
13.3 GaAsSurfaceOxidationandPassivation 409
