Wafer Manufacturing

Imin Kao, is Professor in the Department of Mechanical Engineering at the State University of New York in Stony Brook, USA. He is Faculty Director of the Undergraduate College in Information and Technology Studies. He holds three patents, and his research foci include robotic manipulation with soft contacts and smart contact surface technology using MEMS. Chunhui Chung, is Associate Professor in the Department of Mechanical Engineering at the National Cheng Kung University in Taiwan.

• Preface xiAcknowledgement xiiiPart I From Crystal to Prime Wafers 11 Wafers and Semiconductors 31.1 Introduction 31.2 Semiconductor Revolution 31.2.1 Classification of Materials 31.2.2 Semiconductor Revolution Today 51.2.3 SiliconWafers and Solar Cells 61.3 SiliconWafers Used in Device Manufacturing (IC and MEMS) 71.3.1 StandardWafer Diameters and Sizes 81.3.2 Crystalline Orientation of SiliconWafers 91.3.3 Moore’s Law 111.4 Surface Properties and Quality Measurements ofWafers 111.4.1 SurfaceWaviness: TTV, Bow, andWarp 111.4.2 Discussion onWarp 161.4.3 Automated Measurements of TTV,Warp, Bow, and Flatness 171.4.4 Wafer Flatness 171.4.5 Nanotopography or Nanotopology 211.4.6 Surface Roughness 221.5 Other Properties and Quality Requirements of SiliconWafers 271.5.1 Mechanical and Material Properties 271.5.2 Property of Silicon with Anisotropy 271.5.3 Gravity-induced Deflection ofWafers 301.5.4 Wafer Edge Properties 311.6 Economics ofWafer Manufacturing 321.6.1 Three Categories ofWafers 321.6.2 Cost of SiliconWafers 341.7 Summary 35References 352 Wafer Manufacturing: Generalized Processes and Flow 392.1 Introduction 392.2 Wafer Manufacturing: Generalized Process Flow 392.3 Crystal Growth 412.3.1 Melt Growth 412.3.2 Vapor Growth 492.3.3 Epitaxial Growth 492.3.4 Casting Polycrystalline Crystal 512.3.5 Other Crystal Growth Methods 512.4 Wafer Forming 522.4.1 Cropping 522.4.2 Trimming 522.4.3 Orientation Identification 522.4.4 Slicing 522.4.5 Slicing Using the Inner-diameter (ID) Saw 532.4.6 Slicing Using a Wiresaw 542.4.7 Other Tools for Slicing 552.4.8 Edge Rounding 562.5 Wafer Polishing 562.5.1 Lapping 572.5.2 Grinding 572.5.3 Etching 582.5.4 Polishing 582.6 Wafer Preparation 582.6.1 Cleaning 582.6.2 Inspection 592.6.3 Packaging 592.7 Industrial Processes ofWafer Manufacturing 592.7.1 Crystal Growth 602.7.2 Wafer Forming 612.7.3 Wafer Lapping and Polishing 632.7.4 Wafer Preparation 662.8 Summary 67References 683 Process Modeling and Manufacturing Processes 713.1 Introduction 713.2 Wafer Manufacturing and Brittle Materials 713.3 Ductile Machining Versus Brittle Machining 733.4 Abrasive Machining inWafer Manufacturing 743.4.1 Bonded Abrasive Machining (BAM) 753.4.2 Free Abrasive Machining (FAM) 753.5 Abrasive Materials 763.5.1 Classification of the Grain Size of Abrasive Materials 773.5.2 Hardness of Abrasive Materials 783.5.3 Commonly Used Abrasive Materials inWafer Manufacturing 813.6 Ductile Machining of Brittle Materials 823.6.1 Research on Ductile Machining and Challenges 833.6.2 Opportunity and Future Research 833.7 Process Modeling ofWafer Manufacturing Processes 843.7.1 Rolling-indenting and Scratching-indenting Process Models of FAM 843.7.2 Comparison Between Wiresawing and Lapping 873.7.3 Other Aspects of Engineering Modeling 883.8 Abrasive Slurry in FAM Processes 893.8.1 Composition of Abrasive Slurry 893.8.2 Comparison ofWater and Glycol as a Carrier Fluid for Slurry 903.8.3 Recycling of Abrasive Grits in Slurry 913.9 Summary 93References 93Part II Wafer Forming 974 Wafer Slicing Using a Modern Slurry Wiresaw and Other Saws 994.1 Introduction 994.2 The Modern Wiresaw Technology 1004.2.1 Historical Perspectives of Saws UsingWire 1004.2.2 The Rise of the PV Industry andWafer Slicing 1024.3 The Three Categories of Saw forWafer Slicing 1034.4 Inner-diameter (ID) Saw 1034.5 The Modern Slurry Wiresaw 1054.5.1 The Control and Program Console 1064.5.2 The Wire Management Unit 1064.5.3 Uni-directional Versus Bi-directional Wire Motion 1104.5.4 The Slicing Compartment 1134.5.5 Directions of Ingot Feeding 1144.5.6 Consumables and Other Operations 1164.6 Comparison Between the ID Saw and Wiresaw 1164.7 Research Issues inWiresaw Manufacturing Processes 1204.8 Summary 121References 1215 Modeling of the Wiresaw Manufacturing Process and Material Characteristics 1275.1 Introduction 1275.2 The Rolling-indenting Model 1295.3 Vibration Modeling and Analysis 1315.3.1 A Historical Perspective on the Vibration ofWire 1325.3.2 Equation of Motion of a Moving Wire 1335.3.3 Modal Analysis of an Undamped Moving Wire 1345.3.4 Response for Point-wise Harmonic Excitation 1345.3.5 Natural Frequency of Vibration and Stability 1355.3.6 Numerical Solution Using Galerkin’s Method 1385.3.7 Response of Multiple-point and Distributed Excitations 1395.3.8 Frequency Response of Multiple Excitations 1415.3.9 Vibration Responses of a Moving Wire with Damping 1435.3.10 Discussions 1445.4 Damping Factor of the Slurry Wiresaw Systems 1455.5 Elasto-hydrodynamic Process Modeling 1475.5.1 Approach of Modeling of EHD in the Wiresawing Process 1485.5.2 Theoretical Modeling 1495.5.3 Results of the EHD Analysis 1505.5.4 Implications Related to Floating Machining and Rolling-indenting Modeling of Modern Slurry Wiresaws 1525.5.5 Important Conclusions from EHD Modeling 1555.6 Thermal Management 1565.7 Wire, WireWeb, and Slurry Management 1565.7.1 Real-time and On-line Monitoring of WireWear 1575.7.2 Monitoring the Pitch of the WireWeb Spacing 1605.7.3 Mixing Ratio of Slurry Consisting of Abrasive Grits and Carrier Fluid 1625.8 Summary 162References 1636 Diamond-Impregnated Wire Saws and the Sawing Process 1696.1 Introduction 1696.2 Manufacturing Processes of Diamond-impregnated Wires 1716.2.1 Resinoid Wires 1726.2.2 Electroplated Wires 1746.2.3 Machines and Operations of Diamond Wire Saws 1756.3 Slicing Mechanism of a Diamond Wire Saw 1776.4 Properties ofWafers Sliced by Diamond Wire Saws 1806.4.1 Wafer Surface 1806.4.2 Wafer Fracture Strength 1816.4.3 Residual Stress and Stress Relaxation 1826.4.4 PVWafer Efficiency 1826.4.5 Cost ofWafering 1826.5 Slicing Performance with Different Process Parameters 1836.5.1 Effect of Wire Speed 1836.5.2 Effect of Feed Rate 1836.5.3 Effect of Grain Density 1846.5.4 Effect of Wire Tension 1846.6 Summary 184References 185Part III Wafer Surface Preparation and Management 1897 Lapping 1917.1 Introduction 1917.2 Fundamentals of Lapping and FAM 1927.3 Various Configurations and Types of Lapping Operation 1957.3.1 Single-sided Lapping 2007.3.2 Double-sided Lapping 2017.3.3 Soft-pad Lapping 2017.3.4 Further References 2027.4 Lapping and Preliminary Planarization 2027.4.1 Quality Driven Needs for Preliminary Planarization 2027.4.2 Cost Driven Needs for Preliminary Planarization 2037.5 Technical Challenges and Advances in Lapping 2047.5.1 Technical Considerations 2057.5.2 Advances in Lapping 2067.6 Summary 206References 2078 Chemical Mechanical Polishing 2098.1 Introduction 2098.2 Chemical Mechanical Polishing (CMP) 2108.2.1 Schematic Illustration of the CMP Process and System 2108.2.2 Measurement and Evaluation of the SiliconWafer after Polishing 2138.2.3 Specifications for Polished SiliconWafers 2148.2.4 Types of CMP Processes 2158.2.5 Challenges of CMP Technology 2158.3 Polishing Pad Technology 2158.3.1 Polishing Pad Conditioning 2168.4 Polishing Slurry Technology 2178.5 Edge Polishing 2188.5.1 Fundamentals of Edge Polishing 2188.5.2 Challenges of Edge Polishing 2188.6 Summary 219References 2199 Grinding, Edge Grinding, Etching, and Surface Cleaning 2239.1 Introduction 2239.2 Wafer Grinding for Surface Processing 2239.2.1 Wafer Grinding Methods 2239.2.2 Grinding Wheel Technology 2269.2.3 Types of Grinding Operations 2279.2.4 Technical Challenges and Advances in Grinding 2289.3 Edge Grinding 2289.3.1 Fundamentals of Edge Grinding 2299.3.2 Technical Challenges in Edge Grinding 2319.4 Etching 2319.4.1 Acid Etching 2329.4.2 Caustic Etching 2329.4.3 Preferential Etching 2329.4.4 Technical Challenges and Advances in Etching 2359.5 Surface Cleaning 2369.5.1 Impurities on the Surface of a SiliconWafer 2369.5.2 Various Cleaning Steps inWafer Process Flow 2379.6 RCA Standard Clean 2389.6.1 Introduction 2389.6.2 RCA Cleaning Protocol 2399.6.3 Techniques and Variations of the RCA Method 2409.6.4 The Evolution of SiliconWafer Cleaning Technology 2419.7 Summary 241References 24210 Wafer Metrology and Optical Techniques 24710.1 Introduction 24710.2 Evaluation and Inspection of theWafer Surface 24710.2.1 Wafer Surface Specifications 24710.3 Wafer Defects and Inspection 25110.3.1 Defect Classification 25110.3.2 Impact ofWafer Defects on Device Yield and Performance 25310.3.3 Defect Inspection Techniques and Systems 25410.4 Measurement of theWafer Surface Using Moiré Optical Metrology 25610.4.1 Measurement of theWafer Surface Using Shadow Moiré with the Talbot Effect 25710.4.2 Enhancing the Resolution of Shadow Moiré with “Phase Shifting” 26210.4.3 WireWeb Management Using Optical Metrology Technology 27310.5 Summary 274References 27411 Conclusion 27911.1 (I) From Crystal to PrimeWafers 27911.2 (II) Wafer Forming 28011.3 (III) Wafer Surface Preparation and Management 28111.4 Final Remarks 282Index 283