Fundamentals of Silicon Carbide Technology

Tsunenobu Kimoto, Department of Electronic Science and Engineering, Kyoto University, Japan.Professor Kimoto has been involved in SiC research for more than 20 years and his research activity in this field covers growth, optical and electrical characterization, device processing, device design and fabrication.  He has published more than 300 papers in international journals and has presented more than 50 invited talks at international conferences.  He was a guest editor of the 2008 SiC special issues of IEEE Transactions on Electron Devices. James A Cooper, School of Electrical and Computer Engineering, Purdue University, Indiana, USAProfessor Cooper was a member of technical staff at Bell Laboratories for ten years where he was principal designer of AT&T’s first microprocessor and investigated nonlinear transport in silicon inversion layers.  His research at Purdue has centered on semiconductor device physics and characterization, focusing primarily on III-V materials and silicon carbide.  He has co-authored over 250 technical papers and conference presentations.

• About the Authors xiPreface xiii1 Introduction 11.1 Progress in Electronics 11.2 Features and Brief History of Silicon Carbide 31.2.1 Early History 31.2.2 Innovations in SiC Crystal Growth 41.2.3 Promise and Demonstration of SiC Power Devices 51.3 Outline of This Book 6References 62 Physical Properties of Silicon Carbide 112.1 Crystal Structure 112.2 Electrical and Optical Properties 162.2.1 Band Structure 162.2.2 Optical Absorption Coefficient and Refractive Index 182.2.3 Impurity Doping and Carrier Density 202.2.4 Mobility 232.2.5 Drift Velocity 272.2.6 Breakdown Electric Field Strength 282.3 Thermal and Mechanical Properties 302.3.1 Thermal Conductivity 302.3.2 Phonons 312.3.3 Hardness and Mechanical Properties 322.4 Summary 32References 333 Bulk Growth of Silicon Carbide 393.1 Sublimation Growth 393.1.1 Phase Diagram of Si-C 393.1.2 Basic Phenomena Occurring during the Sublimation (Physical Vapor Transport) Method 393.1.3 Modeling and Simulation 443.2 Polytype Control in Sublimation Growth 463.3 Defect Evolution and Reduction in Sublimation Growth 503.3.1 Stacking Faults 503.3.2 Micropipe Defects 513.3.3 Threading Screw Dislocation 533.3.4 Threading Edge Dislocation and Basal Plane Dislocation 543.3.5 Defect Reduction 573.4 Doping Control in Sublimation Growth 593.4.1 Impurity Incorporation 593.4.2 n-Type Doping 613.4.3 p-Type Doping 613.4.4 Semi-Insulating 623.5 High-Temperature Chemical Vapor Deposition 643.6 Solution Growth 663.7 3C-SiC Wafers Grown by Chemical Vapor Deposition 673.8 Wafering and Polishing 673.9 Summary 69References 694 Epitaxial Growth of Silicon Carbide 754.1 Fundamentals of SiC Homoepitaxy 754.1.1 Polytype Replication in SiC Epitaxy 754.1.2 Theoretical Model of SiC Homoepitaxy 784.1.3 Growth Rate and Modeling 834.1.4 Surface Morphology and Step Dynamics 874.1.5 Reactor Design for SiC Epitaxy 894.2 Doping Control in SiC CVD 904.2.1 Background Doping 904.2.2 n-Type Doping 914.2.3 p-Type Doping 924.3 Defects in SiC Epitaxial Layers 934.3.1 Extended Defects 934.3.2 Deep Levels 1024.4 Fast Homoepitaxy of SiC 1054.5 SiC Homoepitaxy on Non-standard Planes 1074.5.1 SiC Homoepitaxy on Nearly On-Axis {0001} 1074.5.2 SiC Homoepitaxy on Non-basal Planes 1084.5.3 Embedded Homoepitaxy of SiC 1104.6 SiC Homoepitaxy by Other Techniques 1104.7 Heteroepitaxy of 3C-SiC 1114.7.1 Heteroepitaxial Growth of 3C-SiC on Si 1114.7.2 Heteroepitaxial Growth of 3C-SiC on Hexagonal SiC 1144.8 Summary 114References 1155 Characterization Techniques and Defects in Silicon Carbide 1255.1 Characterization Techniques 1255.1.1 Photoluminescence 1265.1.2 Raman Scattering 1345.1.3 Hall Effect and Capacitance–Voltage Measurements 1365.1.4 Carrier Lifetime Measurements 1375.1.5 Detection of Extended Defects 1425.1.6 Detection of Point Defects 1505.2 Extended Defects in SiC 1555.2.1 Major Extended Defects in SiC 1555.2.2 Bipolar Degradation 1565.2.3 Effects of Extended Defects on SiC Device Performance 1615.3 Point Defects in SiC 1655.3.1 Major Deep Levels in SiC 1655.3.2 Carrier Lifetime Killer 1745.4 Summary 179References 1806 Device Processing of Silicon Carbide 1896.1 Ion Implantation 1896.1.1 Selective Doping Techniques 1906.1.2 Formation of an n-Type Region by Ion Implantation 1916.1.3 Formation of a p-Type Region by Ion Implantation 1976.1.4 Formation of a Semi-Insulating Region by Ion Implantation 2006.1.5 High-Temperature Annealing and Surface Roughening 2016.1.6 Defect Formation by Ion Implantation and Subsequent Annealing 2036.2 Etching 2086.2.1 Reactive Ion Etching 2086.2.2 High-Temperature Gas Etching 2116.2.3 Wet Etching 2126.3 Oxidation and Oxide/SiC Interface Characteristics 2126.3.1 Oxidation Rate 2136.3.2 Dielectric Properties of Oxides 2156.3.3 Structural and Physical Characterization of Thermal Oxides 2176.3.4 Electrical Characterization Techniques and Their Limitations 2196.3.5 Properties of the Oxide/SiC Interface and Their Improvement 2346.3.6 Interface Properties of Oxide/SiC on Various Faces 2416.3.7 Mobility-Limiting Factors 2446.4 Metallization 2486.4.1 Schottky Contacts on n-Type and p-Type SiC 2496.4.2 Ohmic Contacts to n-Type and p-Type SiC 2556.5 Summary 262References 2637 Unipolar and Bipolar Power Diodes 2777.1 Introduction to SiC Power Switching Devices 2777.1.1 Blocking Voltage 2777.1.2 Unipolar Power Device Figure of Merit 2807.1.3 Bipolar Power Device Figure of Merit 2817.2 Schottky Barrier Diodes (SBDs) 2827.3 pn and pin Junction Diodes 2867.3.1 High-Level Injection and the Ambipolar Diffusion Equation 2887.3.2 Carrier Densities in the “i” Region 2907.3.3 Potential Drop across the “i” Region 2927.3.4 Current–Voltage Relationship 2937.4 Junction-Barrier Schottky (JBS) and Merged pin-Schottky (MPS) Diodes 296References 3008 Unipolar Power Switching Devices 3018.1 Junction Field-Effect Transistors (JFETs) 3018.1.1 Pinch-Off Voltage 3028.1.2 Current–Voltage Relationship 3038.1.3 Saturation Drain Voltage 3048.1.4 Specific On-Resistance 3058.1.5 Enhancement-Mode and Depletion-Mode Operation 3088.1.6 Power JFET Implementations 3118.2 Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) 3128.2.1 Review of MOS Electrostatics 3128.2.2 MOS Electrostatics with Split Quasi-Fermi Levels 3158.2.3 MOSFET Current–Voltage Relationship 3168.2.4 Saturation Drain Voltage 3198.2.5 Specific On-Resistance 3198.2.6 Power MOSFET Implementations: DMOSFETs and UMOSFETs 3208.2.7 Advanced DMOSFET Designs 3218.2.8 Advanced UMOS Designs 3248.2.9 Threshold Voltage Control 3268.2.10 Inversion Layer Electron Mobility 3298.2.11 Oxide Reliability 3398.2.12 MOSFET Transient Response 342References 3509 Bipolar Power Switching Devices 3539.1 Bipolar Junction Transistors (BJTs) 3539.1.1 Internal Currents 3539.1.2 Gain Parameters 3559.1.3 Terminal Currents 3579.1.4 Current–Voltage Relationship 3599.1.5 High-Current Effects in the Collector: Saturation and Quasi-Saturation 3609.1.6 High-Current Effects in the Base: the Rittner Effect 3669.1.7 High-Current Effects in the Collector: Second Breakdown and the Kirk Effect 3689.1.8 Common Emitter Current Gain: Temperature Dependence 3709.1.9 Common Emitter Current Gain: the Effect of Recombination 3719.1.10 Blocking Voltage 3739.2 Insulated-Gate Bipolar Transistors (IGBTs) 3739.2.1 Current–Voltage Relationship 3749.2.2 Blocking Voltage 3849.2.3 Switching Characteristics 3859.2.4 Temperature Dependence of Parameters 3919.3 Thyristors 3929.3.1 Forward Conducting Regime 3939.3.2 Forward Blocking Regime and Triggering 3989.3.3 The Turn-On Process 4049.3.4 dV/dt Triggering 4069.3.5 The dI/dt Limitation 4079.3.6 The Turn-Off Process 4079.3.7 Reverse-Blocking Mode 415References 41510 Optimization and Comparison of Power Devices 41710.1 Blocking Voltage and Edge Terminations for SiC Power Devices 41710.1.1 Impact Ionization and Avalanche Breakdown 41810.1.2 Two-Dimensional Field Crowding and Junction Curvature 42310.1.3 Trench Edge Terminations 42410.1.4 Beveled Edge Terminations 42510.1.5 Junction Termination Extensions (JTEs) 42710.1.6 Floating Field-Ring (FFR) Terminations 42910.1.7 Multiple-Floating-Zone (MFZ) JTE and Space-Modulated (SM) JTE 43210.2 Optimum Design of Unipolar Drift Regions 43510.2.1 Vertical Drift Regions 43510.2.2 Lateral Drift Regions 43810.3 Comparison of Device Performance 440References 44311 Applications of Silicon Carbide Devices in Power Systems 44511.1 Introduction to Power Electronic Systems 44511.2 Basic Power Converter Circuits 44611.2.1 Line-Frequency Phase-Controlled Rectifiers and Inverters 44611.2.2 Switch-Mode DC–DC Converters 45011.2.3 Switch-Mode Inverters 45311.3 Power Electronics for Motor Drives 45811.3.1 Introduction to Electric Motors and Motor Drives 45811.3.2 dc Motor Drives 45911.3.3 Induction Motor Drives 46011.3.4 Synchronous Motor Drives 46511.3.5 Motor Drives for Hybrid and Electric Vehicles 46811.4 Power Electronics for Renewable Energy 47111.4.1 Inverters for Photovoltaic Power Sources 47111.4.2 Converters for Wind Turbine Power Sources 47211.5 Power Electronics for Switch-Mode Power Supplies 47611.6 Performance Comparison of SiC and Silicon Power Devices 481References 48612 Specialized Silicon Carbide Devices and Applications 48712.1 Microwave Devices 48712.1.1 Metal-Semiconductor Field-Effect Transistors (MESFETs) 48712.1.2 Static Induction Transistors (SITs) 48912.1.3 Impact Ionization Avalanche Transit-Time (IMPATT) Diodes 49612.2 High-Temperature Integrated Circuits 49712.3 Sensors 49912.3.1 Micro-Electro-Mechanical Sensors (MEMS) 49912.3.2 Gas Sensors 50012.3.3 Optical Detectors 504References 509Appendix A Incomplete Dopant Ionization in 4H-SiC 511References 515Appendix B Properties of the Hyperbolic Functions 517Appendix C Major Physical Properties of Common SiC Polytypes 521C. 1 Properties 521C. 2 Temperature and/or Doping Dependence of Major Physical Properties 522References 523Index 525

“Students or working professionals interested in SiC technology will find this book worth reading.”  (IEEE Electrical Insulation Magazine, 1 November 2015)“If you have any interest in the now emerging SiC semiconductor devices, this book covers it all and in sufficient depth to answer questions that might arise from process engineers, device modelers, or power - circuits and systems designers. It really is the book to have on SiC, and because of its breadth as well as depth, would be a good supplement to solid - state physics or electronics books, device design or SPICE modeling, or to provide a solid foundation for circuit design with SiC devices.”  (How2Power.com, 1 March 2015)