Physics and Technology of Crystalline Oxide Semiconductor CAAC-IGZO

Noboru Kimizuka, Kimizuka Institute for Natural Philosophy, PolandNoboru Kimizuka: director of Kimizuka Institute for Natural Philosophy in Poland and adviser of Semiconductor Energy Laboratory, Co., Ltd. He received a Doctor of Science degree from Tokyo Institute of Technology. He joined in the National Institute for Research in Inorganic Materials (NIRIM) of Science and Technology Agency in 1967 (The institute later became the National Institute for Materials Science.) In 1985, he synthesized crystalline IGZO for the first time in the world at NIRIM. Since then, he devoted himself for developing homologous IGZO for about ten years. After he left NIRIM, he served as a researcher and a visiting professor, teaching young people at universities in the U.S., Britain, Mexico, Taiwan, South Korea, and Japan. He is a member of the Chemical Society of Japan, the Ceramic Society of Japan, the Physical Society of Japan, and American Ceramic Society.Shunpei Yamazaki, Semiconductor Energy Laboratory Co., Ltd., Kanagawa, JapanDr. Shunpei Yamazaki is an authority on semiconductors, memory devices, and liquid crystal displays. Listed on over 4,000 US utility patents, Dr. Yamazaki was named in the Guinness Book of World Records as holding the most patents in the world; hailed the most prolific inventor in history by USA Today (in 2005). His most notable work is on the thin-film transistor -- a significant discovery being a crystalline structure in Indium gallium zinc oxide (IGZO) material, which he discovered "by chance" in 2009. Today Dr. Yamazaki is President of the Semiconductor Energy Laboratory (SEL), where he and his team pioneered the unique development of ultra-low-power devices using CAAC-IGZO technology. A joint venture with the Sharp Corporation manufacturing smartphones using crystalline oxide semiconductors (IGZO) is a global first. In 2015 Dr. Yamazaki received the SID (Society for Information Display) Special Recognition Award for "discovering CAAC-IGZO semiconductors, leading its practical application, and paving the way to next-generation displays." His paper on CAAC-IGZO ranked in the top 15 most downloaded papers of Wiley Electrical Engineering and Communications Technology journals, 2014. Dr. Yamazaki is also an IEEE Life Fellow.

• About the Editors ixList of Contributors xiSeries Editor’s Foreword xiiPreface xivAcknowledgments xviiIntroduction xviii1 Layered Compounds in the In 2 O 3 –Ga 2 O 3 –ZnO System and Related Compounds in the Ternary System 11.1 Introduction 11.2 Syntheses and Phase Equilibrium Diagrams 31.2.1 Phase Equilibrium Diagrams in the System R 2 O 3 −Fe 2 O 3 −FeO (R = Y and Yb) 41.2.2 Phase Equilibrium Diagram for the System In 2 O 3 −A 2 O 3 −BO (A = Ga and Fe; B = Zn, Mg, Cu, and Co) 61.2.3 Phase Equilibrium Diagram of the System In 2 O 3 –A 2 O 3 –ZnO (A = Fe and Al) 121.2.4 Other Layered-Structure Compounds 161.3 Crystal Structures 161.3.1 Crystal Structures of InGaO 3 (ZnO) m (m = 1, 2, 3, and 4) 171.3.2 Lattice Constants of InAO 3 (ZnO) m (A = In, Fe, Ga, and Al) 301.3.3 Structural Characteristics of RAO 3 (BO) m Crystals 351.4 Latest Topics in Crystalline IGZO 371.4.1 Interest in Non-conventional Compounds, InGaO3 (ZnO) m(m: non-integral number) 371.4.2 Crystal Structures and Local Structures 381.4.3 Atomic Distribution in Crystalline IGZO(1:1:1.5) 411.4.4 Influence of Composition of Crystalline IGZO 41Appendix 1.A High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy and Annular Bright-Field Scanning Transmission Electron Microscopy 431.a.1 Transmission Electron Microscopy 431.a.2 Scanning Transmission Electron Microscopy 44References 462 Systematic View of CAAC-IGZO and Other Crystalline IGZO Thin Films 502.1 Introduction 502.2 Fabrication Process 532.2.1 Features of CAAC-IGZO 542.2.2 Relation between Deposition Conditions and Crystallinity 542.2.3 Comparison with Other Apparatus 612.2.4 2D-XRD Analysis 622.2.5 Inhibition of Crystal Growth by Impurities 662.2.6 Summary 692.3 Structural Analysis 702.3.1 Features of CAAC-IGZO 702.3.2 Structural Analysis by TEM 722.3.3 Evaluation of Crystal Morphology in CAAC-IGZO 772.3.4 Summary 832.4 Deposition Mechanism 842.4.1 Introduction 842.4.2 Formation of Nanoclusters in CAAC-IGZO Thin Films 882.4.3 Lateral Growth Model of IGZO Nanoclusters 912.4.4 Discussion on Growth Mechanism 942.4.5 Summary 982.5 Structural Stability 982.5.1 Introduction 982.5.2 Electron Diffraction Analysis of CAAC-IGZO and nc-IGZO Films 992.5.3 NBED Analysis of Nanoscale Region in nc-IGZO Film 1002.5.4 Stability Against Electron-Beam Irradiation 1022.5.5 Measurement of Nanoclusters in CAAC-IGZO and nc-IGZO Films 1042.5.6 Influence of Deposition Pressure on Density of IGZO Film 1082.5.7 Chemical Stability 1122.5.8 Summary 1142.6 Single-Crystal and Polycrystalline IGZO 1152.6.1 Introduction 1152.6.2 Crystalline IGZO Formed by Thermal Annealing 1152.6.3 Crystalline IGZO Fabricated by Laser Annealing 1182.7 Researching More Highly Functional IGZO Material 1252.7.1 Homologous Series of IGZO 1252.7.2 Constituent Elements of IGZO and their Influence on Properties 1292.7.3 Selection of High-Mobility IGZO Material in Terms of Solid-Solution Region 1302.7.4 Evaluation Results of IGZO (In : Ga : Zn = 4 : 2 : 3) Film 1302.7.5 CAAC-IGZO FET Characteristics of IGZO(4:2:3) 1342.7.6 Summary 134Appendix 2.A Discovery of CAAC-IGZO 135Appendix 2.B Selected-Area Electron Diffraction and Nano-Beam Electron Diffraction 1372.b.1 Diffraction Method 1372.b.2 Electron Diffraction 138Appendix 2.C Electron Diffraction Simulation of IGZO 142Appendix 2.D Quantitative Evaluation of Alignment of IGZO Using NBED Method 143Appendix 2.E Crystallinity of IGZO Thin Film Deposited by Pulsed Laser Deposition 1472.e.1 Introduction 1472.e.2 Crystallinity of IGZO Thin Film Deposited by Pulsed Laser Deposition 148References 1503 Fundamental Properties of IGZO 1533.1 Introduction 1533.2 Band Structure 1553.2.1 Introduction 1553.2.2 Optical Characteristics and Bandgap 1553.2.3 Band Structure and Effective Mass 1583.2.4 Summary 1613.3 Defect Levels in IGZO Bandgaps 1613.3.1 Introduction 1613.3.2 Evaluation of Oxygen Vacancy and Defect Levels in IGZO Thin Films 1623.3.3 Low-Temperature Photoluminescence 1633.3.4 Constant Photocurrent Method 1633.3.5 Deep Defect Level by Calculation 1673.3.6 Oxygen Vacancy and Crystallinity of IGZO 1703.3.7 Observations of Oxygen in IGZO 1743.3.8 Summary 1773.4 Origin of Main Donor 1793.4.1 Introduction 1793.4.2 Relationship between Hydrogen Concentration and Conductivity 1793.4.3 Quantitative Relationship between Carrier and Hydrogen Concentrations 1823.4.4 Stable Structure for Coexistence of Oxygen Vacancy and Hydrogen 1833.4.5 Energy Level of Donor States 1843.4.6 Thermal Stability of Hydrogen Substituting Oxygen 1853.4.7 Summary 1893.5 Electrical Conduction Mechanisms 1903.5.1 Introduction 1903.5.2 Dominant Scattering Center in Crystalline IGZO 1913.5.3 Theoretical Model of Electron Mobility for In-Rich IGZO 1943.5.4 Conclusion and Some Ideas for Conduction Mechanisms in IGZO 1983.6 Summary 199Appendix 3.A X-Ray Reflectivity and Constant Photocurrent Method 2003.a.1 X-Ray Reflectivity 2003.a.2 Constant Photocurrent Method 202Appendix 3.B First-Principles Calculation Methods 2053.b.1 Search for Stable Distribution of Ga and Zn Atoms in InGaZnO 4 2063.b.2 Formation of Amorphous IGZO Model 2093.b.3 Defect Valuation by Calculation 211References 2144 CAAC-IGZO Field-Effect Transistor 2164.1 Physics of MOSFETs 2164.1.1 Classification of MOSFETs 2174.1.2 Operating Mechanism of CAAC-IGZO FET 2194.1.3 FET Characteristics and Performance Indexes 2294.2 Electrical Characteristics of CAAC-IGZO FET 2324.2.1 Current–Voltage Characteristics of CAAC-IGZO FET 2324.2.2 Normally-Off Threshold Voltage of CAAC-IGZO FET 2354.2.3 Extremely Low Off-State Current of CAAC-IGZO FET 2374.2.4 Frequency Characteristics of CAAC-IGZO FET 2544.3 Comparison between CAAC-IGZO and Si FETs 2584.3.1 Off-State Current 2594.3.2 Saturation Characteristics 2604.3.3 Short-Channel Effects 2634.4 Advantages of CAAC-IGZO as FET Material 2664.4.1 Effects of CAAC Morphology on IGZO Thin-Film and FET Characteristics 2664.4.2 Application to Large-Sized Devices 2724.4.3 Multi-layered CAAC-IGZO 2744.4.4 Impurity Blocking Effects of CAAC-IGZO 2804.5 Summary 281References 2825 Device Application Using CAAC-IGZO 2855.1 Introduction 2855.2 CAAC-IGZO FETs 2865.2.1 Bottom-Gate Top-Contact Structure 2875.2.2 Top-Gate Top-Contact Structure 2925.2.3 Top-Gate Self-aligned Structure 2935.2.4 Summary 2975.3 Application to LSI 2985.4 Application to Displays 3045.5 Market Prospects 309References 309Appendix: Unit Prefix 311Index 312