Magnetic Memory Technology (eBook)

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).

Preface xi

Author Biographies xiv

List of Cited Tables and Figures xvi

1 Basic Electromagnetism 1

1.1 Introduction 1

1.2 Magnetic Force, Pole, Field, and Dipole 1

1.3 Magnetic Dipole Moment, Torque, and Energy 3

1.4 Magnetic Flux and Magnetic Induction 5

1.5 Ampère's Circuital Law, Biot-Savart Law, and Magnetic Field from Magnetic Material 6

1.6 Equations, cgs-SI Unit Conversion Tables 11

2 Magnetism and Magnetic Materials 19

2.1 Introduction 19

2.2 Origin of Magnetization 19

2.3 Classification of Magnetisms 28

2.4 Exchange Interactions 42

2.5 Magnetization in Magnetic Metals and Oxides 49

2.6 Phenomenology of Magnetic Anisotropy 51

2.7 Origins of Magnetic Anisotropy 54

2.8 Magnetic Domain and Domain Walls 57

3 Magnetic Thin Films 67

3.1 Introduction 67

3.2 Magnetic Thin Film Growth 67

3.3 Magnetic Thin Film Characterization 72

4 Magnetoresistance Effects 77

4.1 Introduction 77

4.2 Anisotropic Magnetoresistance (AMR) 78

4.3 Giant Magnetoresistance (GMR) 79

4.4 Tunneling Magnetoresistance (TMR) 81

4.5 Contemporary MTJ Designs and Characterization 84

5 Magnetization Switching and Field MRAMs 93

5.1 Introduction 93

5.2 Magnetization Reversible Rotation and Irreversible Switching Under External Field 93

5.3 Field MRAMs 99

6 Spin Current and Spin Dynamics 105

6.1 Introduction to Hall Effects 105

6.2 Spin Current 109

6.3 Spin Dynamics 116

6.4 Interaction Between Polarized Conduction Electrons and Local Magnetization 124

6.5 Spin Current Interaction with Domain Wall 134

7 Spin-Torque-Transfer (STT) MRAM Engineering 151

7.1 Introduction 151

7.2 Thermal Stability Energy and Switching Energy 152

7.3 STT Switching Properties 154

7.4 The Integrity of MTJ Tunnel Barrier 166

7.5 Data Retention 169

7.6 The Cell Design Considerations and Scaling 173

7.7 MTJ SPICE Models 188

7.8 Test Chip, Test, and Chip-Level Weak Bit Screening 191

8 Advanced Switching MRAM Modes 205

8.1 Introduction 205

8.2 Current-Induced-Domain-Wall Motion (CIDM) Memory 206

8.3 Spin-Orbit Torque (SOT) Memory 211

8.4 Magneto-Electric Effect and Voltage-Control Magnetic Anisotropy (VCMA) MRAM 224

8.5 Relative Merit of Advanced Switching Mode MRAMs 231

9 MRAM Applications and Production 241

9.1 Introduction 241

9.2 Intrinsic Characteristics and Product Attributes of Emerging Nonvolatile Memories 242

9.3 Memory Landscape and MRAM Opportunity 247

9.4 MRAM Production 266

Appendix A Retention Bake (Including Two-Way Flip) 277

Appendix B Memory Functionality-Based Scaling 279

Appendix C High-Bandwidth Design Considerations for STT-MRAM 299

Index 323