Magnetic Memory Technology: Spin-Transfer-Torque Mram and Beyond

ISBN-13: 9781119562238 / Angielski / Twarda / 2021 / 352 str.

Denny D. Tang; Chi-Feng Pai

Spis treści

Preface xiAuthor Biographies xivList of Cited Tables and Figures xvi1 Basic Electromagnetism 11.1 Introduction 11.2 Magnetic Force, Pole, Field, and Dipole 11.3 Magnetic Dipole Moment, Torque, and Energy 31.4 Magnetic Flux and Magnetic Induction 51.5 Ampère's Circuital Law, Biot-Savart Law, and Magnetic Field from Magnetic Material 61.5.1 Ampère's Circuital Law 61.5.2 Biot-Savart's Law 81.5.3 Magnetic Field from Magnetic Material 101.6 Equations, cgs-SI Unit Conversion Tables 11Homework 13References 172 Magnetism and Magnetic Materials 192.1 Introduction 192.2 Origin of Magnetization 192.2.1 From Ampère to Einstein 192.2.2 Precession 212.2.3 Electron Spin 222.2.4 Spin-Orbit Interaction 242.2.5 Hund's Rules 252.3 Classification of Magnetisms 282.3.1 Diamagnetism 302.3.2 Paramagnetism 302.3.3 Ferromagnetism 342.3.4 Antiferromagnetism 372.3.5 Ferrimagnetism 402.4 Exchange Interactions 422.4.1 Direct Exchange 432.4.2 Indirect Exchange: Superexchange 452.4.3 Indirect Exchange: RKKY Interaction 462.4.4 Dzyaloshinskii-Moriya Interaction (DMI) 482.5 Magnetization in Magnetic Metals and Oxides 492.5.1 Slater-Pauling Curve 492.5.2 Rigid Band Model 502.5.3 Iron Oxides and Iron Garnets 512.6 Phenomenology of Magnetic Anisotropy 512.6.1 Uniaxial Anisotropy 522.6.2 Cubic Anisotropy 532.7 Origins of Magnetic Anisotropy 542.7.1 Shape Anisotropy 552.7.2 Magnetocrystalline Anisotropy (MCA) 562.7.3 Perpendicular Magnetic Anisotropy (PMA) 572.8 Magnetic Domain and Domain Walls 572.8.1 Domain Wall 582.8.2 Single Domain and Superparamagnetism 59Homework 60References 643 Magnetic Thin Films 673.1 Introduction 673.2 Magnetic Thin Film Growth 673.2.1 Sputter Deposition 683.2.2 Molecular Beam Epitaxy (MBE) 713.3 Magnetic Thin Film Characterization 723.3.1 Vibrating-Sample Magnetometer (VSM) 733.3.2 Magneto-Optical Kerr Effect (MOKE) 74References 764 Magnetoresistance Effects 774.1 Introduction 774.2 Anisotropic Magnetoresistance (AMR) 784.3 Giant Magnetoresistance (GMR) 794.4 Tunneling Magnetoresistance (TMR) 814.5 Contemporary MTJ Designs and Characterization 844.5.1 Perpendicular MTJ (p-MTJ) 854.5.2 Fully Functional p-MTJ 854.5.3 CIPT Approach for TMR Characterization 87Homework 89References 895 Magnetization Switching and Field MRAMs 935.1 Introduction 935.2 Magnetization Reversible Rotation and Irreversible Switching Under External Field 935.2.1 Magnetization Rotation Under an External Field in the Hard Axis Direction 945.2.2 Magnetization Rotation and Switching Under an external Field in the Easy Axis Direction 955.2.3 Magnetization Rotation and Switching Under Two Orthogonal External Fields 965.2.4 Magnetization Behavior of a Synthetic Anti-ferromagnetic Film Stack 975.3 Field MRAMs 995.3.1 MTJ of Field MRAM 1005.3.2 Half-Select Bit Disturbance Issue 101Homework 102References 1036 Spin Current and Spin Dynamics 1056.1 Introduction to Hall Effects 1056.1.1 Ordinary Hall Effect 1056.1.2 Anomalous Hall Effect and Spin Hall Effect 1066.2 Spin Current 1096.2.1 Electron Spin Polarization in NM/FM/NM Film Stack 1096.2.2 Spin Current Injection, Diffusion, and Inverse Spin Hall Effect 1116.2.3 Generalized Carrier and Spin Current Drift-Diffusion Equation 1146.3 Spin Dynamics 1166.3.1 Landau-Lifshitz and Landau-Lifshitz-Gilbert Equations of Motion 1166.3.2 Ferromagnetic Resonance 1186.3.3 Spin Pumping and Effective Damping in FM/NM Film Stack 1206.3.4 FM/NM/FM Coupling Through Spin Current 1226.4 Interaction Between Polarized Conduction Electrons and Local Magnetization 1246.4.1 Electron Spin Torque Transfer to Local Magnetic Magnetization 1246.4.2 Macrospin Model 1256.4.3 Spin-Torque Transfer in a Spin Valve 1276.4.3.1 Switching Threshold Current Density 1286.4.3.2 Switching Time 1296.4.4 Spin-Torque Transfer Switching in Magnetic Tunnel Junction 1316.4.5 Spin-Torque Ferromagnetic Resonance and Torkance 1336.5 Spin Current Interaction with Domain Wall 1346.5.1 Domain Wall Motion under Spin Current 1356.5.2 Threshold Current Density 137Homework 138References 1447 Spin-Torque-Transfer (STT) MRAM Engineering 1517.1 Introduction 1517.2 Thermal Stability Energy and Switching Energy 1527.3 STT Switching Properties 1547.3.1 Switching Probability and Write Error Rate (WER) 1567.3.2 Switching Current in Precessional Regime 1607.3.3 Switching Delay of an STT-MRAM Cell 1617.3.4 Read Disturb Rate 1617.3.5 Switching Under a Magnetic Field - Phase Diagram 1627.3.6 MTJ Switching Abnormality 1647.3.6.1 Magnetic Back-Hopping 1647.3.6.2 Bifurcation Switching (Ballooning in WER) 1657.3.6.3 Domain Mediated Magnetization Reversal 1667.4 The Integrity of MTJ Tunnel Barrier 1667.4.1 MgO Degradation Model 1677.5 Data Retention 1697.5.1 Retention Determination Based on Bit Switching Probability 1697.5.2 Energy Barrier Determination Based on Aiding Field 1707.5.3 Energy Barrier Extraction with Retention Bake at Chip Level 1717.5.4 Data Retention Fail at the Chip Level 1737.6 The Cell Design Considerations and Scaling 1737.6.1 STT-MRAM Bit Cell and Array 1747.6.2 CMOS Options 1747.6.3 Cell Switching Efficiency 1767.6.4 Cell Design Considerations 1777.6.4.1 WRITE Current and Cell Size 1787.6.4.2 READ Access Performance and RA Product of MTJ 1787.6.4.3 READ and WRITE Voltage Margins 1787.6.4.4 Stray Field Control for Perpendicular MTJ 1797.6.4.5 Suppress Stochastic Switching Time Variation Ideas 1817.6.5 The Scaling of MTJ for Memory 1827.6.5.1 In-Plane MTJ 1837.6.5.2 Out-of-Plane (Perpendicular) MTJ 1847.7 MTJ SPICE Models 1887.7.1 Basic MTJ Equivalent Circuit Model for Circuit Design Simulation 1887.7.2 MTJ SPICE Circuit Model with Embedded Macrospin Calculator 1897.8 Test Chip, Test, and Chip-Level Weak Bit Screening 1917.8.1 Read Marginal Bits 1927.8.2 Write Marginal Bits 1937.8.3 Short Retention Bits 1937.8.4 Low Endurance Bits 194Homework 195References 1978 Advanced Switching MRAM Modes 2058.1 Introduction 2058.2 Current-Induced-Domain-Wall Motion (CIDM) Memory 2068.2.1 Single-Bit Cell 2078.2.2 Multibit Cell: Racetrack 2098.3 Spin-Orbit Torque (SOT) Memory 2118.3.1 Spin Orbit Torque (SOT) MRAM Cells 2118.3.1.1 In-Plane SOT Cell 2128.3.1.2 Perpendicular SOT Cell 2188.3.2 Materials Choice for SOT-MRAM Cell 2198.3.2.1 Transition Metals and their Alloys 2198.3.2.2 Emergent Materials Systems 2218.3.2.3 Benchmarking of SOT Switching Efficiency 2228.4 Magneto-Electric Effect and Voltage-Control Magnetic Anisotropy (VCMA) MRAM 2248.4.1 Magneto-Electric Effects 2248.4.2 VCMA-Assisted MRAMs 2278.4.2.1 VCMA-Assisted Field-MRAM 2278.4.2.2 VCMA-Assisted Multi-bit-Word SOT-MRAM 2298.4.2.3 VCMA-Assisted Precession-Toggle MRAM 2298.5 Relative Merit of Advanced Switching Mode MRAMs 231Homework 233References 2339 MRAM Applications and Production 2419.1 Introduction 2419.2 Intrinsic Characteristics and Product Attributes of Emerging Nonvolatile Memories 2429.2.1 Intrinsic Properties 2439.2.2 Product Attributes 2449.3 Memory Landscape and MRAM Opportunity 2479.3.1 MRAM as Embedded Memory in Logic Chips 2489.3.1.1 Integration Issues of Embedded MRAM 2489.3.1.2 MRAM as Embedded Flash in Microcontroller 2499.3.1.3 Embedded MRAM Cell Size 2509.3.1.4 MRAM as Cache Memory in Processor 2509.3.1.5 Improvement of Access Latency 2519.3.2 High-Density Discrete MRAM 2549.3.2.1 Technology Status 2549.3.2.2 Ideal CMOS Technology for High-Density MRAM 2569.3.2.3 Improvement to Endurance and Write Error Rate with Error Buffer in Chip Architecture 2589.3.3 Applications and Market Opportunity of MRAM 2589.3.3.1 Battery-Backed DRAM Applications 2609.3.3.2 Internet of Things (IoT) and Cybersecurity Applications 2619.3.3.3 Applications to In-Memory Computing, and Artificial Intelligence (AI) 2649.3.3.4 MRAM-Based Memory-Driven Computer 2659.4 MRAM Production 2669.4.1 MRAM Production Ecosystem 2669.4.2 MRAM Product History 2679.4.2.1 First-Generation MRAM - Field MRAM (Also Called Toggle MRAM) 2689.4.2.2 The Second-Generation MRAM - STT-MRAM 2699.4.2.3 The Potential Third-Generation MRAM - SOT MRAM 270Homework 271References 271Appendix A Retention Bake (Including Two-Way Flip) 277Appendix B Memory Functionality-Based Scaling 279Appendix C High-Bandwidth Design Considerations for STT-MRAM 299Index 323

O autorze

DENNY D. TANG, PHD, has been with IBM Watson and later Almaden Research Center, TSMC, and held a position as MRAM Architect in Western Digital. He Is a Live Fellow of IEEE, Fellow of TSMC Academy, a co-author of Magnetic Memory, Fundamentals and Technology, (2010).CHI-FENG PAI, PHD, is now an Associate Professor of National Taiwan University (NTU). He is the recipient of Young Researcher Award of Asian Union of Magnetic Society (AUMS), Young Researcher Fellowship of Ministry of Science and Technology (MOST, Taiwan), and Young Researcher Award of Taiwan Semiconductor Industry Association (TSIA).