Handbook of Wafer Bonding

The focus behind this book on wafer bonding is the fast paced changes in the research and development in three-dimensional (3D) integration, temporary bonding and micro-electro-mechanical systems (MEMS) with new functional layers. Written by authors and edited by a team from microsystems companies and industry-near research organizations, this handbook and reference presents dependable, first-hand information on bonding technologies. Part I sorts the wafer bonding technologies into four categories: Adhesive and Anodic Bonding; Direct Wafer Bonding; Metal Bonding; and Hybrid Metal/Dielectric Bonding. Part II summarizes the key wafer bonding applications developed recently, that is, 3D integration, MEMS, and temporary bonding, to give readers a taste of the significant applications of wafer bonding technologies. This book is aimed at materials scientists, semiconductor physicists, the semiconductor industry, IT engineers, electrical engineers, and libraries.

Table of Contents:
Preface xv Obituary xvii List of Contributors xxi Introduction xxv Part One Technologies 1 A. Adhesive and Anodic Bonding 3 1 Glass Frit Wafer Bonding 3 Roy Knechtel 1.1 Principle of Glass Frit Bonding 3 1.2 Glass Frit Materials 4 1.3 Screen Printing: Process for Bringing Glass Frit Material onto Wafers 5 1.4 Thermal Conditioning: Process for Transforming Printed Paste into Glass for Bonding 8 1.5 Wafer Bond Process: Essential Wafer-to-Wafer Mounting by a Glass Frit Interlayer 11 1.6 Characterization of Glass Frit Bonds 14 1.7 Applications of Glass Frit Wafer Bonding 15 1.8 Conclusions 16 References 17 2 Wafer Bonding Using Spin-On Glass as Bonding Material 19 Viorel Dragoi 2.1 Spin-On Glass Materials 19 2.2 Wafer Bonding with SOG Layers 21 2.2.1 Experimental 21 2.2.2 Wafer Bonding with Silicate SOG Layers 22 2.2.3 Wafer Bonding with Planarization SOG 28 2.2.4 Applications of Adhesive Wafer Bonding with SOG Layers 29 2.2.5 Conclusion 30 References 31 3 Polymer Adhesive Wafer Bonding 33 Frank Niklaus and Jian-Qiang Lu 3.1 Introduction 33 3.2 Polymer Adhesives 34 3.2.1 Polymer Adhesion Mechanisms 34 3.2.2 Properties of Polymer Adhesives 36 3.2.3 Polymer Adhesives for Wafer Bonding 38 3.3 Polymer Adhesive Wafer Bonding Technology 42 3.3.1 Polymer Adhesive Wafer Bonding Process 43 3.3.2 Localized Polymer Adhesive Wafer Bonding 50 3.4 Wafer-to-Wafer Alignment in Polymer Adhesive Wafer Bonding 52 3.5 Examples for Polymer Adhesive Wafer Bonding Processes and Programs 54 3.5.1 Bonding with Thermosetting Polymers for Permanent Wafer Bonds (BCB) or for Temporary Wafer Bonds (mr-I 9000) 54 3.5.2 Bonding with Thermoplastic Polymer (HD-3007) for Temporary and Permanent Wafer Bonds 56 3.6 Summary and Conclusions 57 References 58 4 Anodic Bonding 63 Adriana Cozma Lapadatu and Kari Schjølberg-Henriksen 4.1 Introduction 63 4.2 Mechanism of Anodic Bonding 64 4.2.1 Glass Polarization 64 4.2.2 Achieving Intimate Contact 65 4.2.3 Interface Reactions 66 4.3 Bonding Current 67 4.4 Glasses for Anodic Bonding 68 4.5 Characterization of Bond Quality 69 4.6 Pressure Inside Vacuum-Sealed Cavities 70 4.7 Effect of Anodic Bonding on Flexible Structures 71 4.8 Electrical Degradation of Devices during Anodic Bonding 71 4.8.1 Degradation by Sodium Contamination 72 4.8.2 Degradation by High Electric Fields 73 4.9 Bonding with Thin Films 75 4.10 Conclusions 76 References 77 B. Direct Wafer Bonding 81 5 Direct Wafer Bonding 81 Manfred Reiche and Ulrich Gösele 5.1 Introduction 81 5.2 Surface Chemistry and Physics 82 5.3 Wafer Bonding Techniques 84 5.3.1 Hydrophilic Wafer Bonding 84 5.3.2 Hydrophobic Wafer Bonding 86 5.3.3 Low-Temperature Wafer Bonding 88 5.3.4 Wafer Bonding in Ultrahigh Vacuum 89 5.4 Properties of Bonded Interfaces 90 5.5 Applications of Wafer Bonding 93 5.5.1 Advanced Substrates for Microelectronics 93 5.5.2 MEMS and Nanoelectromechanical Systems 95 5.6 Conclusions 95 References 96 6 Plasma-Activated Bonding 101 Maik Wiemer, Dirk Wuensch, Joerg Braeuer, and Thomas Gessner 6.1 Introduction 101 6.2 Theory 102 6.2.1 (Silicon) Direct Bonding 102 6.2.2 Mechanisms of Plasma on Silicon Surfaces 103 6.2.3 Physical Definition of a Plasma 104 6.3 Classification of PAB 104 6.3.1 Low-Pressure PAB 105 6.3.2 Atmospheric-Pressure PAB 106 6.4 Procedure of PAB 107 6.4.1 Process Flow 107 6.4.2 Characterization Techniques 108 6.4.3 Experiments and Results 110 6.5 Applications for PAB 111 6.5.1 Pressure Sensor 112 6.5.2 Optical Microsystem 112 6.5.3 Microfluidics Packaging 113 6.5.4 Backside-Illuminated CMOS Image Sensor 113 6.5.5 CMOS Compatibility of Low-Pressure PAB 114 6.6 Conclusion 115 References 115 C. Metal Bonding 119 7 Au/Sn Solder 119 Hermann Oppermann and Matthias Hutter 7.1 Introduction 119 7.2 Au/Sn Solder Alloy 120 7.3 Reflow Soldering 127 7.4 Thermode Soldering 130 7.5 Aspects of Three-Dimensional Integration and Wafer-Level Assembly 132 7.6 Summary and Conclusions 135 References 136 8 Eutectic Au–In Bonding 139 Mitsumasa Koyanagi and Makoto Motoyoshi 8.1 Introduction 139 8.2 Organic/Metal Hybrid Bonding 140 8.3 Organic/In–Au Hybrid Bonding 142 8.3.1 In–Au Phase Diagram and Bonding Principle 142 8.3.2 Formation of In–Au Microbumps by a Planarized Liftoff Method 144 8.3.3 Eutectic In–Au Bonding and Epoxy Adhesive Injection 146 8.3.4 Electrical Characteristics of In–Au Microbumps 148 8.4 Three-Dimensional LSI Test Chips Fabricated by Eutectic In–Au Bonding 149 8.5 High-Density and Narrow-Pitch Mircobump Technology 152 8.6 Conclusion 157 Acknowledgment 157 References 157 9 Thermocompression Cu–Cu Bonding of Blanket and Patterned Wafers 161 Kuan-Neng Chen and Chuan Seng Tan 9.1 Introduction 161 9.2 Classification of the Cu Bonding Technique 162 9.2.1 Thermocompression Cu Bonding 162 9.2.2 Surface-Activated Cu Bonding 162 9.3 Fundamental Properties of Cu Bonding 163 9.3.1 Morphology and Oxide Examination of Cu Bonded Layer 163 9.3.2 Microstructure Evolution during Cu Bonding 164 9.3.3 Orientation Evolution during Cu Bonding 165 9.4 Development of Cu Bonding 166 9.4.1 Fabrication and Surface Preparation of Cu Bond Pads 166 9.4.2 Parameters of Cu Bonding 167 9.4.3 Structural Design 168 9.5 Characterization of Cu Bonding Quality 169 9.5.1 Mechanical Tests 169 9.5.2 Image Analysis 170 9.5.3 Electrical Characterization 171 9.5.4 Thermal Reliability 171 9.6 Alignment Accuracy of Cu–Cu Bonding 171 9.7 Reliable Cu Bonding and Multilayer Stacking 172 9.8 Nonblanket Cu–Cu Bonding 174 9.9 Low-Temperature (<300 °C) Cu–Cu Bonding 176 9.10 Applications of Cu Wafer Bonding 178 9.11 Summary 178 References 179 10 Wafer-Level Solid–Liquid Interdiffusion Bonding 181 Nils Hoivik and Knut Aasmundtveit 10.1 Background 181 10.1.1 Solid–Liquid Interdiffusion Bonding Process 181 10.1.2 SLID Bonding Compared with Soldering 182 10.1.3 Material Systems for SLID Bonding 183 10.2 Cu–Sn SLID Bonding 189 10.2.1 Cu–Sn Material Properties and Required Metal Thicknesses 190 10.2.2 Bonding Processes 191 10.2.3 Pretreatment Requirements for SLID Bonding 195 10.2.4 Fluxless Bonding 196 10.3 Au–Sn SLID Bonding 199 10.3.1 Au–Sn Material Properties and Required Metal Thicknesses 199 10.3.2 Bonding Processes 199 10.4 Application of SLID Bonding 201 10.4.1 Cu–Sn Bonding 201 10.4.2 Au–Sn Bonding 204 10.5 Integrity of SLID Bonding 207 10.5.1 Electrical Reliability and Electromigration Testing 207 10.5.2 Mechanical Strength of SLID Bonds 207 10.6 Summary 210 References 212 D. Hybrid Metal/Dielectric Bonding 215 11 Hybrid Metal/Polymer Wafer Bonding Platform 215 Jian-Qiang Lu, J. Jay McMahon, and Ronald J. Gutmann 11.1 Introduction 215 11.2 Three-Dimensional Platform Using Hybrid Cu/BCB Bonding 217 11.3 Baseline Bonding Process for Hybrid Cu/BCB Bonding Platform 220 11.4 Evaluation of Cu/BCB Hybrid Bonding Processing Issues 222 11.4.1 CMP and Bonding of Partially Cured BCB 222 11.4.2 Cu/BCB CMP Surface Profile 223 11.4.3 Hybrid Cu/BCB Bonding Interfaces 224 11.4.4 Topography Accommodation Capability of Partially Cured BCB 227 11.4.5 Electrical Characterization of Hybrid Cu/BCB Bonding 231 11.5 Summary and Conclusions 232 Acknowledgments 233 References 233 12 Cu/SiO2 Hybrid Bonding 237 Léa Di Cioccio 12.1 Introduction 237 12.2 Blanket Cu/SiO2 Direct Bonding Principle 239 12.2.1 Chemical Mechanical Polishing Parameters 239 12.2.2 Bonding Quality and Alignment 243 12.3 Blanket Copper Direct Bonding Principle 245 12.4 Electrical Characterization 251 12.5 Die-to-Wafer Bonding 255 12.5.1 Daisy Chain Structures 256 12.6 Conclusion 257 Acknowledgment 257 References 258 13 Metal/Silicon Oxide Hybrid Bonding 261 Paul Enquist 13.1 Introduction 261 13.2 Metal/Non-adhesive Hybrid Bonding – Metal DBI® 261 13.3 Metal/Silicon Oxide DBI® 262 13.3.1 Metal/Silicon Oxide DBI® Surface Fabrication 263 13.3.2 Metal/Silicon Oxide DBI® Surface Patterning 264 13.3.3 Metal/Silicon Oxide DBI® Surface Topography 264 13.3.4 Metal/Silicon Oxide DBI® Surface Roughness 264 13.3.5 Metal/Silicon Oxide DBI® Surface Activation and Termination 265 13.3.6 Metal/Silicon Oxide DBI® Alignment and Hybrid Surface Contact 265 13.3.7 Metal Parameters Relevant to DBI® Surface Fabrication and Electrical Interconnection 268 13.3.8 DBI® Metal/Silicon Oxide State of the Art 270 13.4 Metal/Silicon Nitride DBI® 271 13.5 Metal/Silicon Oxide DBI® Hybrid Bonding Applications 273 13.5.1 Pixelated 3D ICs 273 13.5.2 Three-Dimensional Heterogeneous Integration 275 13.5.3 CMOS (Ultra) Low-k 3D Integration 276 13.6 Summary 276 References 277 Part Two Applications 279 14 Microelectromechanical Systems 281 Maaike M.V. Taklo 14.1 Introduction 281 14.2 Wafer Bonding for Encapsulation of MEMS 282 14.2.1 Protection during Wafer Dicing 282 14.2.2 Routing of Electrical Signal Lines 282 14.3 Wafer Bonding to Build Advanced MEMS Structures 284 14.3.1 Stacking of Several Wafers 284 14.3.2 Post-processing of Bonded Wafers 285 14.4 Examples of MEMS and Their Requirements for the Bonding Process 286 14.5 Integration of Some Common Wafer Bonding Processes 287 14.5.1 Fusion Bonding of Patterned Wafers 287 14.5.2 Anodic Bonding of Patterned Wafers 290 14.5.3 Eutectic Bonding of Patterned Wafers: AuSn 293 14.6 Summary 297 References 297 15 Three-Dimensional Integration 301 Philip Garrou, James Jian-Qiang Lu, and Peter Ramm 15.1 Definitions 301 15.2 Application of Wafer Bonding for 3D Integration Technology 303 15.3 Motivations for Moving to 3D Integration 305 15.4 Applications of 3D Integration Technology 307 15.4.1 Three-Dimensional Applications by Evolution Not Revolution 307 15.4.2 Microbump Bonding/No TSV 308 15.4.3 TSV Formation/No Stacking 310 15.4.4 Memory 312 15.4.5 Memory on Logic 321 15.4.6 Repartitioning Logic 322 15.4.7 Foundry and OSAT Activity 323 15.4.8 Other 3D Applications 323 15.5 Conclusions 325 References 325 16 Temporary Bonding for Enabling Three-Dimensional Integration and Packaging 329 Rama Puligadda 16.1 Introduction 329 16.2 Temporary Bonding Technology Options 330 16.2.1 Key Requirements 331 16.2.2 Foremost Temporary Wafer Bonding Technologies 332 16.3 Boundary Conditions for Successful Processing 337 16.3.1 Uniform and Void-Free Bonding 337 16.3.2 Protection of Wafer Edges during Thinning and Subsequent Processing 337 16.4 Three-Dimensional Integration Processes Demonstrated with Thermomechanical Debonding Approach 338 16.4.1 Via-Last Process on CMOS Image Sensor Device Wafers 338 16.4.2 Via-Last Process with Aspect Ratio of 2 : 1 341 16.4.3 Via-Last Process with 50 μm Depth Using High-Temperature TEOS Process 341 16.4.4 Die-to-Wafer Stacking Using Interconnect Via Solid–Liquid Interdiffusion Process 342 16.5 Concluding Remarks 343 Acknowledgments 344 References 344 17 Temporary Adhesive Bonding with Reconfiguration of Known Good Dies for Three-Dimensional Integrated Systems 347 Armin Klumpp and Peter Ramm 17.1 Die Assembly with SLID Bonding 347 17.2 Reconfiguration 348 17.3 Wafer-to-Wafer Assembly by SLID Bonding 349 17.4 Reconfiguration with Ultrathin Chips 351 17.5 Conclusion 352 Acknowledgments 353 References 354 18 Thin Wafer Support System for above 250 °C Processing and Cold De-bonding 355 Werner Pamler and Franz Richter 18.1 Introduction 355 18.2 Process Flow 356 18.2.1 Release Layer Processing 357 18.2.2 Carrier Wafer Processing 357 18.2.3 Bonding Process 357 18.2.4 Thinning 359 18.2.5 De-bonding Process 360 18.2.6 Equipment 361 18.3 Properties 361 18.3.1 Device Wafer Thickness 361 18.3.2 Thickness Uniformity 361 18.3.3 Stability 362 18.4 Applications 362 18.4.1 Bonding of Bumped Wafers 363 18.4.2 Packaging of Ultrathin Dies 363 18.4.3 TSV Processing 364 18.4.4 Re-using the Carrier 364 18.5 Conclusions 364 Acknowledgments 365 References 365 19 Temporary Bonding: Electrostatic 367 Christof Landesberger, Armin Klumpp, and Karlheinz Bock 19.1 Basic Principles: Electrostatic Forces between Parallel Plates 367 19.1.1 Electric Fields and Electrostatic Forces in a Plate Capacitor 368 19.1.2 Electrostatic Attraction in a Bipolar Configuration 369 19.1.3 Johnsen–Rahbek Effect 370 19.2 Technological Concept for Manufacture of Mobile Electrostatic Carriers 371 19.2.1 Selection of Substrate Material 371 19.2.2 Selection of Thin-Film Dielectric Layers 372 19.2.3 Electrode Patterns: Materials and Geometry 374 19.2.4 Examples of Mobile Electrostatic Carriers 375 19.3 Characterization of Electrostatic Carriers 376 19.3.1 Electrical and Thermal Properties, Leakage Currents 376 19.3.2 Possible Influence of Electrostatic Fields on CMOS Devices 378 19.4 Electrostatic Carriers for Processing of Thin and Flexible Substrates 379 19.4.1 Handling and Transfer of Thin Semiconductor Wafers 379 19.4.2 Wafer Thinning and Backside Metallization 380 19.4.3 Electrostatic Carriers in Plasma Processing 380 19.4.4 Electrostatic Carriers Enable Bumping of Thin Wafers 380 19.4.5 Electrostatic Carriers in Wet-Chemical Environments 381 19.4.6 Electrostatic Handling of Single Dies 381 19.4.7 Processing of Foils and Insulating Substrates 381 19.5 Summary and Outlook 382 References 383 Index 385