Introduction to magnetic random-access memory

255 Pages·2017·89.29 MB·English

by  Dieny

INTRODUCTION
TO MAGNETIC
RANDOM-ACCESS
MEMORY
IEEEPress
445HoesLane
Piscataway,NJ08854
IEEEPressEditorialBoard
TariqSamad,EditorinChief
GeorgeW.Arnold XiaoouLi RayPerez
GiancarloFortino VladimirLumelsky LindaShafer
DmitryGoldgof Pui-InMak ZidongWang
EkramHossain JeffreyNanzer MengChuZhou
INTRODUCTION
TO MAGNETIC
RANDOM-ACCESS
MEMORY
Edited by
BERNARD DIENY
RONALD B. GOLDFARB
KYUNG-JIN LEE
Copyright2017byTheInstituteofElectricalandElectronicsEngineers,Inc.
PublishedbyJohnWiley&Sons,Inc.,Hoboken,NewJersey.Allrightsreserved
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ISBN:978-1-119-00974-0
PrintedintheUnitedStatesofAmerica
10 9 8 7 6 5 4 3 2 1
CONTENTS
ABOUTTHEEDITORS xi
PREFACE APERSPECTIVEONNONVOLATILEMAGNETIC
MEMORYTECHNOLOGY xiii
CHAPTER1 BASICSPINTRONICTRANSPORTPHENOMENA 1
NicolasLocatelliandVincentCros
1.1 GiantMagnetoresistance 2
1.1.1 BasicsofElectronicTransportinMagneticMaterials 2
1.1.2 ASimpleModeltoDescribeGMR:The“Two-CurrentModel” 5
1.1.3 DiscoveryofGMRandEarlyGMRDevelopments 7
1.1.4 MainApplicationsofGMR 8
1.2 TunnelingMagnetoresistance 9
1.2.1 BasicsofQuantumMechanicalTunneling 10
1.2.2 FirstApproachtoTunnelMagnetoresistance:Jullière’sModel 11
1.2.3 TheSlonczewskiModel 14
1.2.3.1 TheModel 14
1.2.3.2 ExperimentalObservations 15
1.2.3.3 AbouttheTMRAngularDependence 15
1.2.4 MoreComplexModels:TheSpinFilteringEffect 16
1.2.4.1 IncoherentTunnelingThroughanAmorphous(Al O )
2 3
Barrier 16
1.2.4.2 CoherentTunnelingThroughaCrystallineMgO
Barrier 17
1.2.5 BiasDependenceofTunnelMagnetotransport 19
1.3 TheSpin-TransferPhenomenon 20
1.3.1 TheConceptandOriginoftheSpin-TransferEffect 20
1.3.1.1 The“In-Plane”Torque 20
1.3.1.2 The“Out-of-Plane”Torque 23
1.3.2 Spin-Transfer-InducedMagnetizationDynamics 23
1.3.2.1 ASimpleAnalogy 24
1.3.2.2 TowardMRAMBasedonSpin-TransferTorque 25
1.3.3 MainEventsConcerningSpin-TransferAdvances 26
References 27
CHAPTER2 MAGNETICPROPERTIESOFMATERIALSFORMRAM 29
ShinjiYuasa
2.1 MagneticTunnelJunctionsforMRAM 29
2.2 MagneticMaterialsandMagneticProperties 31
v
vi CONTENTS
2.2.1 FerromagnetandAntiferromagnet 31
2.2.2 DemagnetizingFieldandShapeAnisotropy 33
2.2.3 MagnetocrystallineAnisotropy,InterfaceMagneticAnisotropy,
andPerpendicularMagneticAnisotropy 35
2.2.4 ExchangeBias 36
2.2.5 InterlayerExchangeCouplingandSynthetic
AntiferromagneticStructure 37
2.2.6 Spin-ValveStructure 38
2.3 BasicMaterialsandMagnetotransportProperties 39
2.3.1 MetallicNonmagneticSpacerforGMRSpin-Valve 39
2.3.2 MagneticTunnelJunctionwithAmorphousAlOTunnelBarrier 41
2.3.3 MagneticTunnelJunctionwithCrystallineMgO(001)
TunnelBarrier 44
2.3.3.1 EpitaxialMTJwithaSingle-CrystalMgO(001)
Barrier 44
2.3.3.2 CoFeB/MgO/CoFeBMTJwitha(001)-TexturedMgO
BarrierforDeviceApplications 46
2.3.3.3 DeviceApplicationsofMgO-BasedMTJs 48
References 51
CHAPTER3 MICROMAGNETISMAPPLIEDTOMAGNETICNANOSTRUCTURES 55
LilianaD.Buda-Prejbeanu
3.1 MicromagneticTheory:FromBasicConceptsToward
theEquations 55
3.1.1 FreeEnergyofaMagneticSystem 56
3.1.1.1 ExchangeEnergy 56
3.1.1.2 MagnetocrystallineAnisotropyEnergy 57
3.1.1.3 DemagnetizingEnergy 57
3.1.1.4 ZeemanEnergy 60
3.1.2 MagneticallyStableStateandEquilibriumEquations 61
3.1.3 EquationsofMagnetizationMotion 62
3.1.4 LengthScalesinMicromagnetism 63
3.1.5 ModificationRelatedtoSpin-TransferTorquePhenomenaand
Spin–OrbitCoupling 64
3.1.6 ThermalFluctuations 65
3.1.7 NumericalMicromagnetism 66
3.2 MicromagneticConfigurationsinMagneticCircularDots 67
3.3 STT-InducedMagnetizationSwitching:ComparisonofMacrospinand
Micromagnetism 70
3.4 ExampleofMagnetizationPrecessionalSTTSwitching:RoleofDipolar
Coupling 73
References 76
CHAPTER4 MAGNETIZATIONDYNAMICS 79
WilliamE.Bailey
4.1 Landau–Lifshitz–GilbertEquation 79
4.1.1 Introduction 79
4.1.2 VariablesintheEquation 80
CONTENTS vii
4.1.3 TheEquation 81
4.1.3.1 PrecessionalTerm 82
4.1.3.2 RelaxationTerm 83
4.2 Small-AngleMagnetizationDynamics 84
4.2.1 LLGforThin-Film,MagnetizedinPlane,SmallAngles 84
4.2.2 FerromagneticResonance 85
4.2.3 TabulatedMaterialsParameters 87
4.2.3.1 BulkValues 87
4.2.3.2 Finite-SizeEffects 88
4.2.4 PulsedMagnetizationDynamics 89
4.3 Large-AngleDynamics:Switching 90
4.3.1 QuasistaticLimit:Stoner–WohlfarthModel 90
4.3.2 ThermallyActivatedSwitching 93
4.3.3 SwitchingTrajectory 94
4.4 MagnetizationSwitchingbySpin-Transfer 95
4.4.1 AdditionalTermstotheLLG 95
4.4.2 Full-AngleLLGwithSpin-Torque 96
Acknowledgments 97
References 97
CHAPTER5 MAGNETICRANDOM-ACCESSMEMORY 101
BernardDienyandI.LucianPrejbeanu
5.1 IntroductiontoMagneticRandom-AccessMemory(MRAM) 101
5.1.1 HistoricalPerspective 101
5.1.2 VariousCategoriesofMRAM 102
5.2 StorageFunction:MRAMRetention 104
5.2.1 KeyRoleoftheThermalStabilityFactor 104
5.2.2 ThermalStabilityFactorforIn-PlaneandOut-of-Plane
MagnetizedStorageLayer 106
5.3 ReadFunction 110
5.3.1 PrincipleofReadOperation 110
5.3.2 STT-InducedDisturbanceoftheStorageLayerMagneticState
DuringRead 111
5.4 Field-WrittenMRAM(FIMS-MRAM) 112
5.4.1 Stoner–WohlfarthMRAM 112
5.4.2 ToggleMRAM 115
5.4.2.1 ToggleWritePrinciple 115
5.4.2.2 ImprovedWriteMargin 117
5.4.2.3 ApplicationsofToggleMRAM 117
5.4.3 LimitationinDownsizeScalability 118
5.5 Spin-TransferTorqueMRAM(STT-MRAM) 118
5.5.1 PrincipleofSTTWriting 119
5.5.2 ConsiderationsofBreakdown,Write,ReadVoltage
Distributions 122
5.5.3 InfluenceofSTTWritePulseDuration 123
5.5.4 In-PlaneSTT-MRAM 124
5.5.4.1 CriticalCurrentforSwitching 124
5.5.4.2 MinimizationofCriticalCurrentforWriting 125
5.5.5 Out-of-PlaneSTT-MRAM 128
viii CONTENTS
5.5.5.1 BenefitofOut-of-PlaneConfigurationinTermsof
WriteCurrent 130
5.5.5.2 Trade-offBetweenStrongPerpendicularAnisotropy
andLowGilbertDamping 131
5.5.5.3 BenefitfromMagneticMetal/OxidePerpendicular
Anisotropy 131
5.5.5.4 DownsizeScalabilityofPerpendicularSTT-MRAM 133
5.6 Thermally-AssistedMRAM(TA-MRAM) 135
5.6.1 Trade-offBetweenRetentionandWritability;GeneralIdea
ofThermally-AssistedWriting 135
5.6.2 Self-HeatinginMTJDuetoHigh-DensityTunnelingCurrent 136
5.6.3 In-PlaneTA-MRAM 136
5.6.3.1 WriteSelectivityDuetoaCombinationofHeating
andField 136
5.6.3.2 ReducedPowerConsumption,ThankstoLow
WriteFieldandFieldSharing 138
5.6.4 TA-MRAMwithSoftReference:MagneticLogic
Unit(MLU) 140
5.6.4.1 PrincipleofReadingwithSoftReference 141
5.6.4.2 Content-AddressableMemory 143
5.6.5 Thermally-AssistedSTT-MRAM 144
5.6.5.1 In-PlaneSTTPlusTA-MRAM 144
5.6.5.2 Out-of-PlaneSTTPlusTA-MRAM 145
5.7 Three-TerminalMRAMDevices 150
5.7.1 FieldversusCurrent-InducedDomainWall
Propagation 150
5.7.2 PrincipleofWriting 152
5.7.3 AdvantagesandDrawbacksofThree-TerminalDevices 153
5.8 ComparisonofMRAMwithOtherNonvolatileMemory
Technologies 153
5.8.1 MRAMintheInternationalTechnologyRoadmapfor
Semiconductors(ITRS) 153
5.8.2 ComparisonofMRAMandRedox-RAM 155
5.8.3 MainApplicationsofMRAM 155
5.9 Conclusion 157
Acknowledgments 157
References 158
CHAPTER6 MAGNETICBACK-ENDTECHNOLOGY 165
MichaelC.Gaidis
6.1 MagnetoresistiveRandom-AccessMemory(MRAM)Basics 165
6.2 MRAMBack-End-of-LineStructures 166
6.2.1 Field-MRAM 166
6.2.2 Spin-TransferTorque(STT)MRAM 168
6.2.3 OtherMagneticMemoryDeviceStructures 169
6.3 MRAMProcessIntegration 169
6.3.1 TheMagneticTunnelJunction 169
6.3.1.1 SubstratePreparation 171
6.3.1.2 FilmDepositionandAnneal 172
CONTENTS ix
6.3.1.3 DevicePatterning 174
6.3.1.4 DielectricEncapsulation 179
6.3.2 WiringandPackaging 183
6.3.2.1 FerromagneticCladding 184
6.3.2.2 Packaging 186
6.3.3 ProcessingCostConsiderations 186
6.4 ProcessCharacterization 187
6.4.1 200–300mmWaferBlanketMagneticFilms 187
6.4.1.1 Current-in-PlaneTunneling(CIPT) 188
6.4.1.2 KerrMagnetometry 189
6.4.2 ParametricTestofIntegratedMagneticDevices 189
6.4.2.1 MagnetoresistanceversusResistanceandResistance
versusReciprocalArea 190
6.4.2.2 BreakdownVoltage 192
6.4.2.3 DeviceSpreads 194
Acknowledgments 195
References 195
CHAPTER7 BEYONDMRAM:NONVOLATILELOGIC-IN-MEMORYVLSI 199
TakahiroHanyu,TetsuoEndoh,ShojiIkeda,TadahikoSugibayashi,
NaokiKasai,DaisukeSuzuki,MasanoriNatsui,HirokiKoike,andHideoOhno
7.1 Introduction 199
7.1.1 MemoryHierarchyofElectronicSystems 199
7.1.2 CurrentLogicVLSI:TheChallenge 201
7.2 NonvolatileLogic-in-MemoryArchitecture 203
7.2.1 NonvolatileLogic-in-MemoryArchitectureUsingMagnetic
Flip-Flops 205
7.2.2 NonvolatileLogic-in-MemoryArchitectureUsingMTJDevicesin
CombinationwithCMOSCircuits 207
7.3 CircuitSchemeforLogic-in-MemoryArchitectureBasedonMagnetic
Flip-FlopCircuits 209
7.3.1 MagneticFlip-FlopCircuit 209
7.3.2 M-Latch 211
7.4 NonvolatileFullAdderUsingMTJDevicesinCombination
withMOSTransistors 214
7.5 Content-AddressableMemory 217
7.5.1 NonvolatileContent-AddressableMemory 217
7.5.2 NonvolatileTernaryCAMUsingMTJDevicesinCombination
withMOSTransistors 220
7.6 MTJ-basedNonvolatileField-ProgrammableGateArray 224
References 227
APPENDIX UNITSFORMAGNETICPROPERTIES 231
INDEX 233