Introduction to Magnetic Random-Access Memory (eBook)

Bernard Dieny, Ronald B. Goldfarb, Kyung-Jin Lee (Autoren)

eBook Download: PDF

2016
John Wiley & Sons (Verlag)
978-1-119-07935-4 (ISBN)

Infos

Magnetic random-access memory (MRAM) is poised to replace traditional computer memory based on complementary metal-oxide semiconductors (CMOS). MRAM will surpass all other types of memory devices in terms of nonvolatility, low energy dissipation, fast switching speed, radiation hardness, and durability. Although toggle-MRAM is currently a commercial product, it is clear that future developments in MRAM will be based on spin-transfer torque, which makes use of electrons' spin angular momentum instead of their charge. MRAM will require an amalgamation of magnetics and microelectronics technologies. However, researchers and developers in magnetics and in microelectronics attend different technical conferences, publish in different journals, use different tools, and have different backgrounds in condensed-matter physics, electrical engineering, and materials science.

This book is an introduction to MRAM for microelectronics engineers written by specialists in magnetic materials and devices. It presents the basic phenomena involved in MRAM, the materials and film stacks being used, the basic principles of the various types of MRAM (toggle and spin-transfer torque; magnetized in-plane or perpendicular-to-plane), the back-end magnetic technology, and recent developments toward logic-in-memory architectures. It helps bridge the cultural gap between the microelectronics and magnetics communities.

Autor

Bernard Dieny has conducted research in magnetism for 30 years. He played a key role in the pioneering work on spin-valves at IBM Almaden Research Center in 1990-1991. In 2001, he co-founded SPINTEC in Grenoble, France, a public research laboratory devoted to spin-electronic phenomena and components. Dieny is co-inventor of 70 patents and has co-authored more than 340 scientific publications. He received an outstanding achievement award from IBM in 1992 for the development of spin-valves, the European Descartes Prize for Research in 2006, and two Advanced Research Grants from the European Research Council in 2009 and 2015. He is co-founder of two companies, one dedicated to magnetic random-access memory, Crocus Technology, the other to the design of hybrid CMOS/magnetic circuits, EVADERIS. In 2011 he was elected Fellow of the Institute of Electrical and Electronics Engineers. Ronald B. Goldfarb was leader of the Magnetics Group at the National Institute of Standards and Technology in Boulder, Colorado, USA, from 2000 to 2015. He has published over 60 papers, book chapters, and encyclopedia articles in the areas of magnetic measurements, superconductor characterization, and instrumentation. In 2004 he was elected Fellow of the Institute of Electrical and Electronics Engineers (IEEE). From 1995 to 2004 he was editor in chief of IEEE Transactions on Magnetics. He is the founder and chief editor of IEEE Magnetics Letters, established in 2010. He received the IEEE Magnetics Society Distinguished Service Award in 2016. Kyung-Jin Lee is a professor in the Department of Materials Science and Engineering, and an adjunct professor of the KU-KIST Graduate School of Converging Science and Technology, at Korea University. Before joining the university, he worked for Samsung Advanced Institute of Technology in the areas of magnetic recording and magnetic random-access memory. His current research is focused on understanding the underlying physics of current-induced magnetic excitations and exploring new spintronic devices utilizing spin-transfer torque. He is co-inventor of 20 patents and has more than 100 scientific publications in the areas of magnetic random-access memory, spin-transfer torque, and spin-orbit torques. He received an outstanding patent award from the Korea Patent Office in 2005 and an award for Excellent Research on Basic Science from the Korean government in 2010. In 2013 he was recognized by the National Academy of Engineering of Korea as a leading scientist in spintronics, "one of the top 100 technologies of the future."

Inhalt

Introduction to Magnetic Random-Access Memory 1
Contents 7
About the Editors 13
Preface: A Perspective on Nonvolatile Magnetic Memory Technology 15
References 19
Chapter 1: Basic Spintronic Transport Phenomena 21
1.1 Giant Magnetoresistance 22
1.1.1 Basics of Electronic Transport in Magnetic Materials 22
1.1.2 A Simple Model to Describe GMR: The "Two-Current Model" 25
1.1.3 Discovery of GMR and Early GMR Developments 27
1.1.4 Main Applications of GMR 28
1.2 Tunneling Magnetoresistance 29
1.2.1 Basics of Quantum Mechanical Tunneling 30
1.2.2 First Approach to Tunnel Magnetoresistance: Jullière's Model 31
1.2.3 The Slonczewski Model 34
1.2.3.1 The Model 34
1.2.3.2 Experimental Observations 35
1.2.3.3 About the TMR Angular Dependence 35
1.2.4 More Complex Models: The Spin Filtering Effect 36
1.2.4.1 Incoherent Tunneling Through an Amorphous (Al2O3) Barrier 36
1.2.4.2 Coherent Tunneling Through a Crystalline MgO Barrier 37
1.2.5 Bias Dependence of Tunnel Magnetotransport 39
1.3 The Spin-Transfer Phenomenon 40
1.3.1 The Concept and Origin of the Spin-Transfer Effect 40
1.3.1.1 The "In-Plane" Torque 40
1.3.1.2 The "Out-of-Plane" Torque 43
1.3.2 Spin-Transfer-Induced Magnetization Dynamics 43
1.3.2.1 A Simple Analogy 44
1.3.2.2 Toward MRAM Based on Spin-Transfer Torque 45
1.3.3 Main Events Concerning Spin-Transfer Advances 46
References 47
Chapter 2: Magnetic Properties of Materials for MRAM 49
2.1 Magnetic Tunnel Junctions for MRAM 49
2.2 Magnetic Materials and Magnetic Properties 51
2.2.1 Ferromagnet and Antiferromagnet 51
2.2.2 Demagnetizing Field and Shape Anisotropy 53
2.2.3 Magnetocrystalline Anisotropy, Interface Magnetic Anisotropy, and Perpendicular Magnetic Anisotropy 55
2.2.4 Exchange Bias 56
2.2.5 Interlayer Exchange Coupling and Synthetic Antiferromagnetic Structure 57
2.2.6 Spin-Valve Structure 58
2.3 Basic Materials and Magnetotransport Properties 59
2.3.1 Metallic Nonmagnetic Spacer for GMR Spin-Valve 59
2.3.2 Magnetic Tunnel Junction with Amorphous AlO Tunnel Barrier 61
2.3.3 Magnetic Tunnel Junction with Crystalline MgO(0 0 1) Tunnel Barrier 64
2.3.3.1 Epitaxial MTJ with a Single-Crystal MgO(0 0 1) Barrier 64
2.3.3.2 CoFeB/MgO/CoFeB MTJ with a (0 0 1)-Textured MgO Barrier for Device Applications 66
2.3.3.3 Device Applications of MgO-Based MTJs 68
References 71
Chapter 3: Micromagnetism Applied to Magnetic Nanostructures 75
3.1 Micromagnetic Theory: From Basic Concepts Toward the Equations 75
3.1.1 Free Energy of a Magnetic System 76
3.1.1.1 Exchange Energy 76
3.1.1.2 Magnetocrystalline Anisotropy Energy 77
3.1.1.3 Demagnetizing Energy 77
3.1.1.4 Zeeman Energy 80
3.1.2 Magnetically Stable State and Equilibrium Equations 81
3.1.3 Equations of Magnetization Motion 82
3.1.4 Length Scales in Micromagnetism 83
3.1.5 Modification Related to Spin-Transfer Torque Phenomena and Spin–Orbit Coupling 84
3.1.6 Thermal Fluctuations 85
3.1.7 Numerical Micromagnetism 86
3.2 Micromagnetic Configurations in Magnetic Circular Dots 87
3.3 STT-Induced Magnetization Switching: Comparison of Macrospin and Micromagnetism 90
3.4 Example of Magnetization Precessional STT Switching: Role of Dipolar Coupling 93
References 96
Chapter 4: Magnetization Dynamics 99
4.1 Landau–Lifshitz–Gilbert Equation 99
4.1.1 Introduction 99
4.1.2 Variables in the Equation 100
4.1.3 The Equation 101
4.1.3.1 Precessional Term 102
4.1.3.2 Relaxation Term 103
4.2 Small-Angle Magnetization Dynamics 104
4.2.1 LLG for Thin-Film, Magnetized in Plane, Small Angles 104
4.2.2 Ferromagnetic Resonance 105
4.2.3 Tabulated Materials Parameters 107
4.2.3.1 Bulk Values 107
4.2.3.2 Finite-Size Effects 108
4.2.4 Pulsed Magnetization Dynamics 109
4.3 Large-Angle Dynamics: Switching 110
4.3.1 Quasistatic Limit: Stoner–Wohlfarth Model 110
4.3.2 Thermally Activated Switching 113
4.3.3 Switching Trajectory 114
4.4 Magnetization Switching by Spin-Transfer 115
4.4.1 Additional Terms to the LLG 115
4.4.2 Full-Angle LLG with Spin-Torque 116
Acknowledgments 117
References 117
Chapter 5: Magnetic Random-Access Memory 121
5.1 Introduction to Magnetic Random-Access Memory (MRAM) 121
5.1.1 Historical Perspective 121
5.1.2 Various Categories of MRAM 122
5.2 Storage Function: MRAM Retention 124
5.2.1 Key Role of the Thermal Stability Factor 124
5.2.2 Thermal Stability Factor for In-Plane and Out-of-Plane Magnetized Storage Layer 126
5.3 Read Function 130
5.3.1 Principle of Read Operation 130
5.3.2 STT-Induced Disturbance of the Storage Layer Magnetic State During Read 131
5.4 Field-Written MRAM (FIMS-MRAM) 132
5.4.1 Stoner–Wohlfarth MRAM 132
5.4.2 Toggle MRAM 135
5.4.2.1 Toggle Write Principle 135
5.4.2.2 Improved Write Margin 137
5.4.2.3 Applications of Toggle MRAM 137
5.4.3 Limitation in Downsize Scalability 138
5.5 Spin-Transfer Torque MRAM (STT-MRAM) 138
5.5.1 Principle of STT Writing 139
5.5.2 Considerations of Breakdown, Write, Read Voltage Distributions 142
5.5.3 Influence of STT Write Pulse Duration 143
5.5.4 In-Plane STT-MRAM 144
5.5.4.1 Critical Current for Switching 144
5.5.4.2 Minimization of Critical Current for Writing 145
5.5.5 Out-of-Plane STT-MRAM 148
5.5.5.1 Benefit of Out-of-Plane Configuration in Terms of Write Current 150
5.5.5.2 Trade-off Between Strong Perpendicular Anisotropy and Low Gilbert Damping 151
5.5.5.3 Benefit from Magnetic Metal/Oxide Perpendicular Anisotropy 151
5.5.5.4 Downsize Scalability of Perpendicular STT-MRAM 153
5.6 Thermally-Assisted MRAM (TA-MRAM) 155
5.6.1 Trade-off Between Retention and Writability General Idea of Thermally-Assisted Writing
5.6.2 Self-Heating in MTJ Due to High-Density Tunneling Current 156
5.6.3 In-Plane TA-MRAM 156
5.6.3.1 Write Selectivity Due to a Combination of Heating and Field 156
5.6.3.2 Reduced Power Consumption, Thanks to Low Write Field and Field Sharing 158
5.6.4 TA-MRAM with Soft Reference: Magnetic Logic Unit (MLU) 160
5.6.4.1 Principle of Reading with Soft Reference 161
5.6.4.2 Content-Addressable Memory 163
5.6.5 Thermally-Assisted STT-MRAM 164
5.6.5.1 In-Plane STT Plus TA-MRAM 164
5.6.5.2 Out-of-Plane STT Plus TA-MRAM 165
5.7 Three-Terminal MRAM Devices 170
5.7.1 Field versus Current-Induced Domain Wall Propagation 170
5.7.2 Principle of Writing 172
5.7.3 Advantages and Drawbacks of Three-Terminal Devices 173
5.8 Comparison of MRAM With Other Nonvolatile Memory Technologies 173
5.8.1 MRAM in the International Technology Roadmap for Semiconductors (ITRS) 173
5.8.2 Comparison of MRAM and Redox-RAM 175
5.8.3 Main Applications of MRAM 175
5.9 Conclusion 177
Acknowledgments 177
References 178
Chapter 6: Magnetic Back-End Technology 185
6.1 Magnetoresistive Random-Access Memory (MRAM) Basics 185
6.2 MRAM Back-End-of-Line Structures 186
6.2.1 Field-MRAM 186
6.2.2 Spin-Transfer Torque (STT) MRAM 188
6.2.3 Other Magnetic Memory Device Structures 189
6.3 MRAM Process Integration 189
6.3.1 The Magnetic Tunnel Junction 189
6.3.1.1 Substrate Preparation 191
6.3.1.2 Film Deposition and Anneal 192
6.3.1.3 Device Patterning 194
6.3.1.4 Dielectric Encapsulation 199
6.3.2 Wiring and Packaging 203
6.3.2.1 Ferromagnetic Cladding 204
6.3.2.2 Packaging 206
6.3.3 Processing Cost Considerations 206
6.4 Process Characterization 207
6.4.1 200–300 mm Wafer Blanket Magnetic Films 207
6.4.1.1 Current-in-Plane Tunneling (CIPT) 208
6.4.1.2 Kerr Magnetometry 209
6.4.2 Parametric Test of Integrated Magnetic Devices 209
6.4.2.1 Magnetoresistance versus Resistance and Resistance versus Reciprocal Area 210
6.4.2.2 Breakdown Voltage 212
6.4.2.3 Device Spreads 214
Acknowledgments 215
References 215
Chapter 7: Beyond MRAM: Nonvolatile Logic-in-Memory VLSI 219
7.1 Introduction 219
7.1.1 Memory Hierarchy of Electronic Systems 219
7.1.2 Current Logic VLSI: The Challenge 221
7.2 Nonvolatile Logic-In-Memory Architecture 223
7.2.1 Nonvolatile Logic-in-Memory Architecture Using Magnetic Flip-Flops 225
7.2.2 Nonvolatile Logic-in-Memory Architecture Using MTJ Devices in Combination with CMOS Circuits 227
7.3 Circuit Scheme for Logic-In-Memory Architecture Based on Magnetic Flip-Flop Circuits 229
7.3.1 Magnetic Flip-Flop Circuit 229
7.3.2 M-Latch 231
7.4 Nonvolatile Full Adder Using MTJ Devices in Combination With MOS Transistors 234
7.5 Content-Addressable Memory 237
7.5.1 Nonvolatile Content-Addressable Memory 237
7.5.2 Nonvolatile Ternary CAM Using MTJ Devices in Combination with MOS Transistors 240
7.6 MTJ-Based Nonvolatile Field-Programmable Gate Array 244
References 247
Appendix: Units for Magnetic Properties 251
Index 253
End User License Agreement 263

Produkt-Details

• Erscheint lt. Verlag: 14.11.2016
• Sprache: englisch
• Themenwelt: Informatik ► Weitere Themen ► Hardware
• Themenwelt: Naturwissenschaften ► Physik / Astronomie ► Atom- / Kern- / Molekularphysik
• Themenwelt: Naturwissenschaften ► Physik / Astronomie ► Festkörperphysik
• Themenwelt: Technik ► Elektrotechnik / Energietechnik
• Schlagworte: Electrical & Electronics Engineering • Elektrotechnik u. Elektronik • fundamentals of magnetic materials • fundamentals of magnetic technology • fundamentals of MRAM • Halbleiter • Halbleiterphysik • introduction to MRAM • Magnetic random access memory • Magnetics • magnetism • Magnetismus • microelectronics • MRAM • Physics • Physik • Semiconductor physics • semiconductors
• ISBN-10: 1-119-07935-7 / 1119079357
• ISBN-13: 978-1-119-07935-4 / 9781119079354