Handbook of Thin Film Materials

Handbook of Thin Film Materials Volume 1 Deposition and Processing of Thin Films Edited by Hari Singh Nalwa, M.Sc, Ph.D. Stanford Scientific Corporation Los Angeles, California, USA Formerly at Hitachi Research Laboratory Hitachi Ltd., Ibaraki, Japan ACADEMIC PRESS A Division of Harcourt, Inc. San Diego San Francisco New York Boston London Sydney Tokyo

Contents About the Editor List of Contributors Volume Listing xix xxi xxiii Chapter 1. METHODS OF DEPOSITION OF HYDROGENATED AMORPHOUS SILICON FOR DEVICE APPLICATIONS Wilfried G. J. H. M. van Sark 1. Introduction 2 1.1. Historical Overview 3 1.2. Material Aspects of Hydrogenated Amorphous Silicon 3 2. Research and Industrial Equipment 8 2.1. General Aspects 8 2.2. Reactor Configurations 9 2.3. Scale-Up to Systems of Industrial Size 10 2.4. ASTER, a Research System 11 3. Physics and Chemistry of PECVD 14 3.1. General Introduction 14 3.2. Plasma Physics 15 3.3. Plasma Chemistry 18 4. Plasma Modeling 21 4.1. ID Fluid Discharge Model 21 4.2. 2D Fluid Discharge Model 30 4.3. Particle-in-Cell Discharge Models 33 5. Plasma Analysis 39 5.1. Optical Emission 39 5.2. Electrostatic Probes 40 5.3. Mass Spectrometry 42 5.4. Ellipsometry 51 6. Relation between Plasma Parameters and Material Properties 53 6.1. External Parameters 53 6.2. Internal Parameters 55 7. Deposition Models 63 7.1. Surface Adsorption 64 7.2. Solubility of Hydrogen in Silicon 65 7.3. Elimination of Hydrogen from a-si:h 65 7.4. Dangling-Bond and Weak-Bond Density 67 8. Modifications of PECVD 67 8.1. VHF 68 8.2. Chemical Annealing 73 8.3. RF Modulation 74 9. Hot Wire Chemical Vapor Deposition 76 9.1. General Description 76 9.2. Experimental Setup 77 9.3. Material Properties and Deposition Conditions 78 9.4. Deposition Model 79 10. Expanding Thermal Plasma Chemical Vapor Deposition 79 10.1. General Description 79 10.2. Experimental Setup 80 10.3. Material Properties and Deposition Conditions 81 XI

xii CONTENTS 10.4. Deposition Model 82 11. Applications 82 11.1. SolarCells 82 11.2. Thin Film Transistors 86 11.3. Light Sensors 87 11.4. Chemical Sensors 88 11.5. Other Applications 89 12. Conclusion 91 Acknowledgments 92 References 92 Chapter 2. ATOMIC LAYER DEPOSITION Mikko Ritala, Магкки Leskelä 1. Introduction 103 2. Alternative Names 104 3. Basic Features of ALD 104 3.1. ALD Cycle 104 3.2. Benefits of ALD 106 3.3. Limitations of ALD 108 4. ALD Reactors 108 4.1. Overview 108 4.2. Flow-Type ALD Reactors with Inert Gas Valving 109 4.3. Flow-Type ALD Reactors with Moving Substrates 112 5. ALD Precursors 113 5.1. Requirements for ALD Precursors 113 5.2. Choice of Precursors 121 5.3. Overview of Precursors and Their Combinations Used in ALD 121 6. Film Materials and Applications 125 6.1. Electroluminescent Display Phosphors 126 6.2. Insulators 128 6.3. Transparent Conductors 133 6.4. Passivating and Protecting Layers 134 6.5. Transition Metal Nitride Diffusion Barriers 135 6.6. Metals 137 6.7. Solar Cell Absorbers 138 6.8. Optical Coatings 138 7. Characterization of ALD Processes 138 7.1. Film Growth Experiments 139 7.2. Reaction Mechanism Studies 144 8. Summary 152 References 153 Chapter 3. LASER APPLICATIONS IN TRANSPARENT CONDUCTING OXIDE THIN FILMS PROCESSING Frederick Ojo Adurodija 1. Introduction 162 1.1. History of Transparent Conducting Films and Applications 162 1.2. Indium Tin Oxide Thin Films 162 1.3. Deposition Techniques 162 1.4. General Remarks 162 2. General Electrical Properties of TCO Films 163 2.1. Conduction Mechanism 163 2.2. Defect Models 164 3. Excimer Lasers 164 3.1. Principles of Excimer Lasers 165 3.2. Principles of Excimer PLD 166 3.3. Major Applications of Excimer Lasers 166 3.4. Advantages and Disadvantages of PLD 166

CONTENTS хш 4. PLD Deposition Technique 167 4.1. ITO Target Ablation and Modification 167 4.2. Background Gas 168 4.3. Growth Rate and Film Thickness 170 4.4. Target to Substrate Distance 170 4.5. Optimization of Deposition Conditions (Background Gas) 171 4.6. Initial Growth of ITO Films 172 4.7. Film Deposition and Characterization 174 5. Properties of PLD Indium Oxide Films 175 5.1. Electrical Properties 175 5.2. Optical Properties 177 5.3. Structural Properties 177 6. Properties of PLD ITO Films 177 6.1. Structural and Other Properties 177 6.2. Electrical Properties of ITO Films 184 6.3. Optical Properties 188 6.4. Chemical States Analysis of ITO Films 191 7. Laser Irradiation 193 7.1. Excimer Laser Irradiation of Thin Films 193 7.2. Laser Irradiation of ITO Films 195 7.3. Film Preparation by Laser Irradiation 196 7.4. Effect of Sn-Doping on the Electrical Properties of Laser-Irradiated ITO Films 196 7.5. Effects of Oxygen Pressure on the Properties of Laser-Irradiated ITO Films 200 7.6. Effect of Substrate Temperature on the Properties of Laser-Irradiated ITO Films 205 8. Other TCO Materials Zinc Oxide (ZnO) Thin Films 208 9. Applications of PLD ITO Films 212 10. Conclusion 213 References 213 Chapter 4. COLD PLASMA PROCESSES IN SURFACE SCIENCE AND TECHNOLOGY Pierangelo Gröning 1. Introduction 219 1.1. Plasma the Fourth State of Matter 219 1.2. Cold Plasma 221 2. Applications 226 2.1. Carbon Thin Films 226 2.2. Plasma Polymerization 236 2.3. Surface Treatments 240 2.4. Surface Termination by H2 Plasma Treatment 253 3. Outlook 257 Acknowledgments 257 References 257 Chapter 5. ELECTROCHEMICAL FORMATION OF THIN FILMS OF BINARY HI-V COMPOUNDS L. Peraldo Bicelli, V. M. Kozlov 1. Introduction 262 2. Group III-V Compounds 263 3. Electrodeposition 266 4. Codeposition: Basic Considerations 266 4.1. Thermodynamic Aspects 266 4.2. Kinetic Aspects 270 5. Codeposition from Aqueous Solutions 271 5.1. Pourbaix's Equilibrium Diagrams 271 5.2. Parasitic Reactions 273 5.3. Classification of Cathodic Codeposition Processes 274 6. Codeposition from Molten Salts 275

XIV CONTENTS 7. Sequential Electrodeposition 276 8. Electrodeposition of Group III-V Compounds 277 8.1. Aluminum Compounds 278 8.2. Gallium Phosphide 279 8.3. Indium Phosphide 280 8.4. Gallium Arsenide 283 8.5. Indium Arsenide 293 8.6. Gallium Antimonide 297 8.7. Indium Antimonide 299 8.8. Indium-Bismuth Compounds 303 9. Diffusion Process and Formation of Group III-V Compounds, 304 9.1. The Indium-Bismuth System 304 9.2. The Indium-Antimony System 308 10. Influence of the Substrate Structure and Morphology on the Diffusion Process 310 10.1. The Indium-Antimony System 310 10.2. The Gallium-Antimony System 312 10.3. Amorphous Antimony Crystallization 313 11. Conclusions 313 Acknowledgments 315 References 315 Chapter 6. FUNDAMENTALS FOR THE FORMATION AND STRUCTURE CONTROL OF THIN FILMS: NUCLEATION, GROWTH, SOLID-STATE TRANSFORMATIONS Hideya Kumomi, Frank G. Shi 1. Introduction 319 1.1. Structures and Properties 319 1.2. Structures and Formation Process 320 1.3. Nucleation, Growth, and Solid-State Transformations 320 1.4. Scope of This Chapter 320 2. Theory of Nucleation and Growth 321 2.1. Thermodynamics of Nucleation and Growth 321 2.2. Kinetics of Nucleation and Growth 323 2.3. Observables in Nucleation and Growth 333 3. Measurement of Nucleation and Growth 338 3.1. Dimensions 338 3.2. Ratios 342 3.3. Rates 345 3.4. Characteristic Time 347 3.5. Energy Barriers 347 4. Control of Nucleation and Growth 352 4.1. Grain Size 352 4.2. Size Distribution of Grains 361 4.3. Grain Locations 362 Acknowledgments 369 References 370 Chapter 7. ION IMPLANT DOPING AND ISOLATION OF GaN AND RELATED MATERIALS S. J. Pearton 1. Introduction 375 2. Range Statistics 375 3. Donor Implants (Si, O, S, Se, and Те) 376 4. Acceptor Implants 380 5. Damage Removal 381 6. High Temperature Annealing 385 6.1. Surface Protection 385 6.2. Susceptors 387

CONTENTS xv 6.3. A1N Encapsulant 388 6.4. NH 3 Annealing 392 7. Diffusivity of Implanted Species 393 8. p-n Junction Formation 396 9. Isolation 397 10. Devices 405 Acknowledgment 406 References 406 Chapter 8. PLASMA ETCHING OF GaN AND RELATED MATERIALS S. J. Pearton, R. J. Shut 1. Introduction 409 2. Plasma Reactors 410 2.1. Reactive Ion Etching 410 2.2. High-Density Plasmas 410 2.3. Chemically Assisted Ion Beam Etching 412 2.4. Reactive Ion Beam Etching 412 2.5. Low-Energy Electron-Enhanced Etching 412 3. Plasma Chemistries 413 3.1. Cl 2 -Based 413 3.2. I 2 -and Br 2 -Based 418 3.3. CH 4 /H 2 /Ar 422 4. Etch Profile And Etched Surface Morphology 424 5. Plasma-Induced Damage 425 5.1. n-gan 426 5.2. p-gan 430 5.3. Schotfky Diodes 434 5.4. p-n Junctions 438 6. Device Processing 441 6.1. Microdisk Lasers 441 6.2. Ridge Waveguide Lasers 441 6.3. Heterojunction Bipolar Transistors 443 6.4. Field Effect Transistors 446 6.5. UV Detectors 448 Acknowledgments 450 References 450 Chapter 9. RESIDUAL STRESSES IN PHYSICALLY VAPOR-DEPOSITED THIN FILMS Yves Pauleau 1. Introduction 455 2. Microstructure and Morphology of PVD Thin Films 457 2.1. Nucleation and Growth Modes of PVD Thin Films 457 2.2. Effect of Energetic Particle Condensation and/or Bombardment on Nucleation and Early Stages of the Growth of Films 458 2.3. Structure-Zone Models 459 2.4. Major Physical Parameters Affecting the Microstructure of PVD Films 462 3. Magnitude of Residual Stresses in PVD Thin Films 470 3.1. Determination of Residual Stresses from the Radius of Curvature of Substrates 470 3.2. Determination of Residual Stresses Using X-Ray Diffraction Techniques... 474 3.3. Magnitude of Residual Stresses in Multilayer Structures 477 3.4. Mechanical Stability of PVD Thin Films 478 4. Origin of Residual Stresses in PVD Thin Films 482 4.1. Thermal Stresses 482 4.2. Intrinsic Stresses 484 4.3. Extrinsic Stresses 490 5. Effect of Major Process Parameters on the Intrinsic Stress 492 5.1. Pressure Effect 493

XVI CONTENTS 5.2. Substrate Bias Voltage Effect 494 5.3. Substrate Temperature Effect 495 6. Data on Residual Stresses in PVD Thin Films 497 6.1. Residual Stresses in Silicon Dioxide Films Prepared by Thermal Evaporation 497 6.2. Residual Stresses in Silicon Dioxide Films Produced by Ion-Assisted Deposition 505 6.3. Residual Stresses in Silicon Oxynitride Films Produced by Dual Ion Beam Sputtering 507 6.4. Amorphous Carbon Films Deposited by Conventional Magnetron Sputtering on Grounded Substrates 510 6.5. Amorphous Carbon Films Deposited by Conventional and Unbalanced Magnetron Sputtering on Biased Substrates 515 7. Summary and Conclusion 519 References 520 Chapter 10. LANGMUIR-BLODGETT FILMS OF BIOLOGICAL MOLECULES Victor Erokhin 1. Introduction 523 2. Principles of the Langmuir-Blodgett Technique 524 2.1. Monolayers at the Air-Water Interface 524 2.2. Monolayer Transfer onto Solid Substrates 526 3. Techniques for Studying Monolayers and LB Films 528 3.1. Monolayers at the Air-Water Interface 528 3.2. LB Films on Solid Supports 529 4. Protein Films 533 4.1. Protein Monolayers at the Air-Water Interface 533 4.2. Monolayer Transfer 538 4.3. Protein Layers on Solid Substrates 538 4.4. Thermal Stability of Proteins in LB Films 543 5. Conclusions 544 Acknowledgment 545 References 545 Chapter 11. STRUCTURE FORMATION DURING ELECTROCRYSTALLIZATION OF METAL FILMS V. M. Kozlov, L. Peraldo Bicelli 1. Introduction 559 2. Classification of the Structural Defects in Electrodeposits 560 3. Mechanism of Formation of Structural Defects during Noncoherent Nucleation 563 4. Classical Theory of Noncoherent Nucleation 566 5. Atomistic Analysis of Noncoherent Nucleation 570 6. Factors Influencing the Structure of Electrodeposits (Theoretical and Experimental Results) 574 6.1. Influence of the Crystallization Overvoltage on the Structure of Electrodeposits 574 6.2. Influence of the Foreign Particle Adsorption on the Structure of Electrodeposits 576 6.3. Influence of the Nature of Metals on the Formation of the Polycrystalline Structure of the Deposit during Electrocrystallization 580 7. Mechanism of Multitwinning 582 8. Conclusions 584 Acknowledgment 585 References 585 Chapter 12. EPITAXIAL THIN FILMS OF INTERMETALLIC COMPOUNDS Michael Huth 1. Introduction 587 2. MBE Growth of Intermetallic Compounds 588 2.1. Intermetallic Compounds: Definition of Terms 588 2.2. Equipment 588

CONTENTS xvii 2.3. General Considerations in Compound Growth 593 2.4. Phase Stabilization and Orientation Selection 594 2.5. Epitaxial Strain 601 2.6. Morphological Aspects 604 3. Selected Applications in Basic and Applied Research 608 3.1. Superconductivity in UPd2Al3 608 3.2. Magnetoelastic Coupling Effects in RFe2 611 3.3. Magnetization Reversal of Ultrathin Co-Pt Heterostructures 615 3.4. Intermetallic Compounds for Magnetooptics 618 3.5. Exchange Anisotropy with Metallic Antiferromagnets 618 3.6. Antiferromagnetic Order Parameter Nucleation on a Thin Film Surface 619 3.7. Order-Disorder Phenomena 620 4. Outlook 623 Acknowledgments 623 References 624 Chapter 13. PULSED LASER DEPOSITION OF THIN FILMS: EXPECTATIONS AND REALITY Leonid R. Shaginyan 1. Introduction 627 2. Composition of Pulsed Laser-Deposited Films 629 2.1. Dependence of the Composition of PLD Films on Laser and Deposition Processing Parameters 630 2.2. Dependence of the Composition of PLD Films on the Evaporating Material 631 2.3. Experimental Details of Pilyankevich et al 634 2.4. Formation of PLD Film Composition 643 2.5. Conclusions 650 3. Structure of PLD Films 651 3.1. Factors Influencing the PLD Film Structure 651 3.2. Role of Molecules and Larger Clusters 651 3.3. Gas-Phase Clustering 652 3.4. Crystallization Temperature as an Index of Film Structure "Perfection" 653 3.5. Influence of Laser Parameters and Substrate Temperature on Epitaxial Growth of PLD Films 655 3.6. Ways to Control the PLD Film Structure 658 3.7. Conclusions 659 4. Polymorphism in PLD Films 659 4.1. Polymorphism of PLD Carbon Films 659 4.2. Polymorphism of Boron Nitride Films 660 4.3. Polymorphism of Silicon Carbide Films 661 4.4. Conclusions 661 5. Macrodefects in PLD Films 661 5.1. Mechanisms of Splashing 661 5.2. Elimination of Particulates 662 5.3. Determination of Vapor Portion in Products of Laser-Ablated Metals 662 5.4. Conclusions 666 6. Influence of Target Properties on Some Features of PLD Compound Films 666 6.1. Role of Target Thermal Conductivity in Compound Film Property Formation 667 6.2. Powder Targets: Mechanisms of Particulate Generation 668 6.3. Conclusions 670 7. General Conclusions 670 Acknowledgments 671 References 671 Chapter 14. SINGLE-CRYSTAL ß'-ALUMINA FILMS Chu Кип Kuo, Patrick S. Nicholson 1. Introduction 675 2. Review of the Literature on Large-Area Thin Films of ^'Iß-AliO^ 677

XVlll CONTENTS 3. Na-/S"-Al 2 0 3 Single-Crystal Film Growth 677 3.1. Sapphire Substrate 678 3.2. Vaporization Source 679 3.3. Alkali Vapor-Sapphire Substrate Reactions 679 3.4. у8"-а1 2 Оз Film Growth Kinetics 681 4. Single-Crystal Film Characterization 681 4.1. X-Ray Diffraction 682 4.2. Microscopy 682 4.3. Structural Transformation from a-to ^"-А^Оз 684 5. Na-/S"-Al 2 0 3 -Coated, a-al 2 0 3 Single-Crystal Platelets 687 6. The Growth of К-уб'-А^Оз Single-Crystal Films 688 7. Ion Exchange Preparation of Other ^"-А^Оз Isomorphs in Single-Crystal Film Form... 689 7.1. Ion Exchange 689 7.2. The Optical Refractivity of ^"-А^Оз Isomorphs 691 8. Luminescence Investigation of Cu + -Doped, Single-Crystal ^"-АЬЮз Films 691 8.1. Luminescence 691 8.2. Luminescence Patterning of Single-Crystal ^"-А^Оз Films 692 9. Summary 694 10. Appendix 694 10.1. ß"- and /S-A1 2 0 3 Isomorphs 694 10.2. Optical Refractivity of ß" - and /S-A1 2 0 3 695 10.3. Luminescence of Activated ^"(^-А^Оз 697 Acknowledgment 697 References 697 Index 699