Magnetic Memory Technology: Spin-transfer-Torque MRAM and Beyond

344 Pages·2021·15.218 MB·English

by  Denny D. Tang, Chi-Feng Pai

Magnetic Memory
Technology
IEEEPress
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SaeidNahavandi JeffreyReed DiomidisSpinellis
SarahSpurgeon AhmetMuratTekalp
Magnetic Memory Technology
Spin-Transfer-Torque MRAM and Beyond
DennyD. Tang
Tang Consultancy
Chi-Feng Pai
National Taiwan University
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LibraryofCongressCataloging-in-PublicationData
Names:Tang,DennyD.,author.|Pai,Chi-Feng,author.|JohnWiley&
Sons,Inc.,publisher.
Title:Magneticmemorytechnology:spin-transfer-torqueMRAMandbeyond/
DennyD.Tang,Chi-FengPai.
Description:Hoboken:Wiley-IEEEPress,[2021]|Includesbibliographical
referencesandindex.
Identifiers:LCCN2020033767(print)|LCCN2020033768(ebook)|ISBN
9781119562238(cloth)|ISBN9781119562221(adobepdf)|ISBN
9781119562283(epub)
Subjects:LCSH:Magneticmemory(Computers).|Spintronics.|Nonvolatile
random-accessmemory.
Classification:LCCTK7895.M3T3652021 (print)|LCCTK7895.M3 (ebook)|
DDC621.39/763–dc23
LCrecordavailableathttps://lccn.loc.gov/2020033767
LCebookrecordavailableathttps://lccn.loc.gov/2020033768
CoverDesign:Wiley
CoverImage:FractalimagecourtesyofDennyD.Tang,(insetimage)IEEE
10 9 8 7 6 5 4 3 2 1
v
Contents
Preface xi
AuthorBiographies xiv
ListofCitedTablesandFigures xvi
1 BasicElectromagnetism 1
1.1 Introduction 1
1.2 MagneticForce,Pole,Field,andDipole 1
1.3 MagneticDipoleMoment,Torque,andEnergy 3
1.4 MagneticFluxandMagneticInduction 5
1.5 Ampère’sCircuitalLaw,Biot-SavartLaw,andMagneticFieldfrom
MagneticMaterial 6
1.5.1 Ampère’sCircuitalLaw 6
1.5.2 Biot-Savart’sLaw 8
1.5.3 MagneticFieldfromMagneticMaterial 10
1.6 Equations,cgs-SIUnitConversionTables 11
Homework 13
References 17
2 MagnetismandMagneticMaterials 19
2.1 Introduction 19
2.2 OriginofMagnetization 19
2.2.1 FromAmpèretoEinstein 19
2.2.2 Precession 21
2.2.3 ElectronSpin 22
2.2.4 Spin-OrbitInteraction 24
2.2.5 Hund’sRules 25
2.3 ClassificationofMagnetisms 28
2.3.1 Diamagnetism 30
2.3.2 Paramagnetism 30
vi Contents
2.3.3 Ferromagnetism 34
2.3.4 Antiferromagnetism 37
2.3.5 Ferrimagnetism 40
2.4 ExchangeInteractions 42
2.4.1 DirectExchange 43
2.4.2 IndirectExchange:Superexchange 45
2.4.3 IndirectExchange:RKKYInteraction 46
2.4.4 Dzyaloshinskii-MoriyaInteraction(DMI) 48
2.5 MagnetizationinMagneticMetalsandOxides 49
2.5.1 Slater-PaulingCurve 49
2.5.2 RigidBandModel 50
2.5.3 IronOxidesandIronGarnets 51
2.6 PhenomenologyofMagneticAnisotropy 51
2.6.1 UniaxialAnisotropy 52
2.6.2 CubicAnisotropy 53
2.7 OriginsofMagneticAnisotropy 54
2.7.1 ShapeAnisotropy 55
2.7.2 MagnetocrystallineAnisotropy(MCA) 56
2.7.3 PerpendicularMagneticAnisotropy(PMA) 57
2.8 MagneticDomainandDomainWalls 57
2.8.1 DomainWall 58
2.8.2 SingleDomainandSuperparamagnetism 59
Homework 60
References 64
3 MagneticThinFilms 67
3.1 Introduction 67
3.2 MagneticThinFilmGrowth 67
3.2.1 SputterDeposition 68
3.2.2 MolecularBeamEpitaxy(MBE) 71
3.3 MagneticThinFilmCharacterization 72
3.3.1 Vibrating-SampleMagnetometer(VSM) 73
3.3.2 Magneto-OpticalKerrEffect(MOKE) 74
References 76
4 MagnetoresistanceEffects 77
4.1 Introduction 77
4.2 AnisotropicMagnetoresistance(AMR) 78
4.3 GiantMagnetoresistance(GMR) 79
4.4 TunnelingMagnetoresistance(TMR) 81
Contents vii
4.5 ContemporaryMTJDesignsandCharacterization 84
4.5.1 PerpendicularMTJ(p-MTJ) 85
4.5.2 FullyFunctionalp-MTJ 85
4.5.3 CIPTApproachforTMRCharacterization 87
Homework 89
References 89
5 MagnetizationSwitchingandFieldMRAMs 93
5.1 Introduction 93
5.2 MagnetizationReversibleRotationandIrreversibleSwitchingUnder
ExternalField 93
5.2.1 MagnetizationRotationUnderanExternalFieldintheHardAxis
Direction 94
5.2.2 MagnetizationRotationandSwitchingUnderanexternalField
intheEasyAxisDirection 95
5.2.3 MagnetizationRotationandSwitchingUnderTwoOrthogonal
ExternalFields 96
5.2.4 MagnetizationBehaviorofaSyntheticAnti-ferromagneticFilm
Stack 97
5.3 FieldMRAMs 99
5.3.1 MTJofFieldMRAM 100
5.3.2 Half-SelectBitDisturbanceIssue 101
Homework 102
References 103
6 SpinCurrentandSpinDynamics 105
6.1 IntroductiontoHallEffects 105
6.1.1 OrdinaryHallEffect 105
6.1.2 AnomalousHallEffectandSpinHallEffect 106
6.2 SpinCurrent 109
6.2.1 ElectronSpinPolarizationinNM/FM/NMFilmStack 109
6.2.2 SpinCurrentInjection,Diffusion,andInverseSpinHallEffect 111
6.2.3 GeneralizedCarrierandSpinCurrentDrift-DiffusionEquation 114
6.3 SpinDynamics 116
6.3.1 Landau-LifshitzandLandau-Lifshitz-GilbertEquationsof
Motion 116
6.3.2 FerromagneticResonance 118
6.3.3 SpinPumpingandEffectiveDampinginFM/NMFilmStack 120
6.3.4 FM/NM/FMCouplingThroughSpinCurrent 122
6.4 InteractionBetweenPolarizedConductionElectronsandLocal
Magnetization 124
viii Contents
6.4.1 ElectronSpinTorqueTransfertoLocalMagneticMagnetization 124
6.4.2 MacrospinModel 125
6.4.3 Spin-TorqueTransferinaSpinValve 127
6.4.3.1 SwitchingThresholdCurrentDensity 128
6.4.3.2 SwitchingTime 129
6.4.4 Spin-TorqueTransferSwitchinginMagneticTunnelJunction 131
6.4.5 Spin-TorqueFerromagneticResonanceandTorkance 133
6.5 SpinCurrentInteractionwithDomainWall 134
6.5.1 DomainWallMotionunderSpinCurrent 135
6.5.2 ThresholdCurrentDensity 137
Homework 138
References 144
7 Spin-Torque-Transfer(STT)MRAMEngineering 151
7.1 Introduction 151
7.2 ThermalStabilityEnergyandSwitchingEnergy 152
7.3 STTSwitchingProperties 154
7.3.1 SwitchingProbabilityandWriteErrorRate(WER) 156
7.3.2 SwitchingCurrentinPrecessionalRegime 160
7.3.3 SwitchingDelayofanSTT-MRAMCell 161
7.3.4 ReadDisturbRate 161
7.3.5 SwitchingUnderaMagneticField–PhaseDiagram 162
7.3.6 MTJSwitchingAbnormality 164
7.3.6.1 MagneticBack-Hopping 164
7.3.6.2 BifurcationSwitching(BallooninginWER) 165
7.3.6.3 DomainMediatedMagnetizationReversal 166
7.4 TheIntegrityofMTJTunnelBarrier 166
7.4.1 MgODegradationModel 167
7.5 DataRetention 169
7.5.1 RetentionDeterminationBasedonBitSwitchingProbability 169
7.5.2 EnergyBarrierDeterminationBasedonAidingField 170
7.5.3 EnergyBarrierExtractionwithRetentionBakeatChipLevel 171
7.5.4 DataRetentionFailattheChipLevel 173
7.6 TheCellDesignConsiderationsandScaling 173
7.6.1 STT-MRAMBitCellandArray 174
7.6.2 CMOSOptions 174
7.6.3 CellSwitchingEfficiency 176
7.6.4 CellDesignConsiderations 177
7.6.4.1 WRITECurrentandCellSize 178
7.6.4.2 READAccessPerformanceandRAProductofMTJ 178
Contents ix
7.6.4.3 READandWRITEVoltageMargins 178
7.6.4.4 StrayFieldControlforPerpendicularMTJ 179
7.6.4.5 SuppressStochasticSwitchingTimeVariationIdeas 181
7.6.5 TheScalingofMTJforMemory 182
7.6.5.1 In-PlaneMTJ 183
7.6.5.2 Out-of-Plane(Perpendicular)MTJ 184
7.7 MTJSPICEModels 188
7.7.1 BasicMTJEquivalentCircuitModelforCircuitDesignSimulation 188
7.7.2 MTJSPICECircuitModelwithEmbeddedMacrospinCalculator 189
7.8 TestChip,Test,andChip-LevelWeakBitScreening 191
7.8.1 ReadMarginalBits 192
7.8.2 WriteMarginalBits 193
7.8.3 ShortRetentionBits 193
7.8.4 LowEnduranceBits 194
Homework 195
References 197
8 AdvancedSwitchingMRAMModes 205
8.1 Introduction 205
8.2 Current-Induced-Domain-WallMotion(CIDM)Memory 206
8.2.1 Single-BitCell 207
8.2.2 MultibitCell:Racetrack 209
8.3 Spin-OrbitTorque(SOT)Memory 211
8.3.1 SpinOrbitTorque(SOT)MRAMCells 211
8.3.1.1 In-PlaneSOTCell 212
8.3.1.2 PerpendicularSOTCell 218
8.3.2 MaterialsChoiceforSOT-MRAMCell 219
8.3.2.1 TransitionMetalsandtheirAlloys 219
8.3.2.2 EmergentMaterialsSystems 221
8.3.2.3 BenchmarkingofSOTSwitchingEfficiency 222
8.4 Magneto-ElectricEffectandVoltage-ControlMagneticAnisotropy
(VCMA)MRAM 224
8.4.1 Magneto-ElectricEffects 224
8.4.2 VCMA-AssistedMRAMs 227
8.4.2.1 VCMA-AssistedField-MRAM 227
8.4.2.2 VCMA-AssistedMulti-bit-WordSOT-MRAM 229
8.4.2.3 VCMA-AssistedPrecession-ToggleMRAM 229
8.5 RelativeMeritofAdvancedSwitchingModeMRAMs 231
Homework 233
References 233
x Contents
9 MRAMApplicationsandProduction 241
9.1 Introduction 241
9.2 IntrinsicCharacteristicsandProductAttributesofEmergingNonvolatile
Memories 242
9.2.1 IntrinsicProperties 243
9.2.2 ProductAttributes 244
9.3 MemoryLandscapeandMRAMOpportunity 247
9.3.1 MRAMasEmbeddedMemoryinLogicChips 248
9.3.1.1 IntegrationIssuesofEmbeddedMRAM 248
9.3.1.2 MRAMasEmbeddedFlashinMicrocontroller 249
9.3.1.3 EmbeddedMRAMCellSize 250
9.3.1.4 MRAMasCacheMemoryinProcessor 250
9.3.1.5 ImprovementofAccessLatency 251
9.3.2 High-DensityDiscreteMRAM 254
9.3.2.1 TechnologyStatus 254
9.3.2.2 IdealCMOSTechnologyforHigh-DensityMRAM 256
9.3.2.3 ImprovementtoEnduranceandWriteErrorRatewithErrorBufferin
ChipArchitecture 258
9.3.3 ApplicationsandMarketOpportunityofMRAM 258
9.3.3.1 Battery-BackedDRAMApplications 260
9.3.3.2 InternetofThings(IoT)andCybersecurityApplications 261
9.3.3.3 ApplicationstoIn-MemoryComputing,andArtificial
Intelligence(AI) 264
9.3.3.4 MRAM-BasedMemory-DrivenComputer 265
9.4 MRAMProduction 266
9.4.1 MRAMProductionEcosystem 266
9.4.2 MRAMProductHistory 267
9.4.2.1 First-GenerationMRAM–FieldMRAM(AlsoCalledToggle
MRAM) 268
9.4.2.2 TheSecond-GenerationMRAM–STT-MRAM 269
9.4.2.3 ThePotentialThird-GenerationMRAM–SOTMRAM 270
Homework 271
References 271
AppendixA RetentionBake(IncludingTwo-WayFlip) 277
AppendixB MemoryFunctionality-BasedScaling 279
AppendixC High-BandwidthDesignConsiderationsfor
STT-MRAM 299
Index 323