3D and Circuit Integration of MEMS Explore heterogeneous circuit integration and the packaging needed for practical applications of microsystems MEMS and system integration are important building blocks for the “More-Than-Moore” paradigm described in the International Technology Roadmap for Semiconductors. And, in 3D and Circuit Integration of MEMS, distinguished editor Dr. Masayoshi Esashi delivers a comprehensive and systematic exploration of the technologies for microsystem packaging and heterogeneous integration. The book focuses on the silicon MEMS that have been used extensively and the technologies surrounding system integration. You’ll learn about topics as varied as bulk micromachining, surface micromachining, CMOS-MEMS, wafer interconnection, wafer bonding, and sealing. Highly relevant for researchers involved in microsystem technologies, the book is also ideal for anyone working in the microsystems industry. It demonstrates the key technologies that will assist researchers and professionals deal with current and future application bottlenecks. Readers will also benefit from the inclusion of: A thorough introduction to enhanced bulk micromachining on MIS process, including pressure sensor fabrication and the extension of MIS process for various advanced MEMS devices An exploration of epitaxial poly Si surface micromachining, including process condition of epi-poly Si, and MEMS devices using epi-poly Si Practical discussions of Poly SiGe surface micromachining, including SiGe deposition and LP CVD polycrystalline SiGe A concise treatment of heterogeneously integrated aluminum nitride MEMS resonators and filters Perfect for materials scientists, electronics engineers, and electrical and mechanical engineers, 3D and Circuit Integration of MEMS will also earn a place in the libraries of semiconductor physicists seeking a one-stop reference for circuit integration and the practical application of microsystems.

Table of Contents:
Part I Introduction 1 1 Overview 3 Masayoshi Esashi References 10 Part II System on Chip 13 2 Bulk Micromachining 15 Xinxin Li and Heng Yang 2.1 Process Basis of Bulk Micromachining Technologies 16 2.2 Bulk Micromachining Based on Wafer Bonding 20 2.2.1 SOI MEMS 20 2.2.2 Cavity SOI Technology 27 2.2.3 Silicon on Glass Processes: Dissolved Wafer Process (DWP) 29 2.3 Single-Wafer Single-Side Processes 34 2.3.1 Single-Crystal Reactive Etching and Metallization Process (SCREAM) 34 2.3.2 Sacrificial Bulk Micromachining (SBM) 38 2.3.3 Silicon on Nothing (SON) 40 References 45 3 Enhanced Bulk Micromachining Based on MIS Process 49 Xinxin Li and Heng Yang 3.1 Repeating MIS Cycle for Multilayer 3D structures or Multi-sensor Integration 49 3.1.1 Pressure Sensors with PS3 Structure 49 3.1.2 P+G Integrated Sensors 52 3.2 Pressure Sensor Fabrication – From MIS Updated to TUB 54 3.3 Extension of MIS Process for Various Advanced MEMS Devices 58 References 58 4 Epitaxial Poly Si Surface Micromachining 61 Masayoshi Esashi 4.1 Process Condition of Epi-poly Si 61 4.2 MEMS Devices Using Epi-poly Si 61 References 67 5 Poly-SiGe Surface Micromachining 69 Carrie W. Low, Sergio F. Almeida, Emmanuel P. Quévy, and Roger T. Howe 5.1 Introduction 69 5.1.1 SiGe Applications in IC and MEMS 70 5.1.2 Desired SiGe Properties for MEMS 70 5.2 SiGe Deposition 70 5.2.1 Deposition Methods 70 5.2.2 Material Properties Comparison 71 5.2.3 Cost Analysis 72 5.3 LPCVD Polycrystalline SiGe 73 5.3.1 Vertical Furnace 73 5.3.2 Particle Control 75 5.3.3 Process Monitoring and Maintenance 75 5.3.4 In-line Metrology for Film Thickness and Ge Content 76 5.3.5 Process Space Mapping 77 5.4 CMEMS® Process 78 5.4.1 CMOS Interface Challenges 79 5.4.2 CMEMS Process Flow 80 5.4.2.1 Top Metal Module 80 5.4.2.2 Plug Module 84 5.4.2.3 Structural SiGe Module 85 5.4.2.4 Slit Module 85 5.4.2.5 Structure Module 85 5.4.2.6 Spacer Module 85 5.4.2.7 Electrode Module 85 5.4.2.8 Pad Module 86 5.4.3 Release 86 5.4.4 Al–Ge Bonding for Microcaps 87 5.5 Poly-SiGe Applications 88 5.5.1 Resonator for Electronic Timing 88 5.5.2 Nano-electro-mechanical Switches 92 References 94 6 Metal Surface Micromachining 99 Minoru Sasaki 6.1 Background of Surface Micromachining 99 6.2 Static Device 100 6.3 Static Structure Fixed after the Single Movement 101 6.4 Dynamic Device 103 6.4.1 MEMS Switch 103 6.4.2 Digital Micromirror Device 104 6.5 Summary 111 References 111 7 Heterogeneously Integrated Aluminum Nitride MEMS  Resonators and Filters 113 Enes Calayir, Srinivas Merugu, Jaewung Lee, Navab Singh, and Gianluca Piazza 7.1 Overview of Integrated Aluminum Nitride MEMS 113 7.2 Heterogeneous Integration of Aluminum Nitride MEMS Resonators with CMOS Circuits 114 7.2.1 Aluminum Nitride MEMS Process Flow 115 7.2.2 Encapsulation of Aluminum Nitride MEMS Resonators and Filters 116 7.2.3 Redistribution Layers on Top of Encapsulated Aluminum Nitride MEMS 118 7.2.4 Selected Individual Resonator and Filter Frequency Responses 119 7.2.5 Flip-chip Bonding of Aluminum Nitride MEMS with CMOS 121 7.3 Heterogeneously Integrated Self-Healing Filters 123 7.3.1 Application of Statistical Element Selection (SES) to AlN MEMS Filters with CMOS Circuits 123 7.3.2 Measurement of 3D Hybrid Integrated Chip Stack 124 References 127 8 MEMS Using CMOS Wafer 131 Weileun Fang, Sheng-Shian Li, Yi Chiu, and Ming-Huang Li 8.1 Introduction: CMOS MEMS Architectures and Advantages 131 8.2 Process Modules for CMOS MEMS 139 8.2.1 Process Modules for Thin Films 140 8.2.1.1 Metal Sacrificial 140 8.2.1.2 Oxide Sacrificial 142 8.2.1.3 TiN-composite (TiN-C) 143 8.2.2 Process Modules for the Substrate 145 8.2.2.1 SF6 and XeF2 (Dry Isotropic) 145 8.2.2.2 KOH and TMAH (Wet Anisotropic) 146 8.2.2.3 RIE and DRIE (Front-side RIE, Backside DRIE) 146 8.3 The 2P4M CMOS Platform (0.35 μm) 148 8.3.1 Accelerometer 148 8.3.2 Pressure Sensor 149 8.3.3 Resonators 150 8.3.4 Others 152 8.4 The 1P6M CMOS Platform (0.18 μm) 154 8.4.1 Tactile Sensors 154 8.4.2 IR Sensor 156 8.4.3 Resonators 158 8.4.4 Others 160 8.5 CMOS MEMS with Add-on Materials 164 8.5.1 Gas and Humidity Sensors 164 8.5.1.1 Metal Oxide 164 8.5.1.2 Polymer 170 8.5.2 Biochemical Sensors 173 8.5.3 Pressure and Acoustic Sensors 175 8.5.3.1 Microfluidic Structures 178 8.6 Monolithic Integration of Circuits and Sensors 180 8.6.1 Multi-sensor Integration 180 8.6.1.1 Gas Sensors 180 8.6.1.2 Physical Sensors 181 8.6.2 Readout Circuit Integration 183 8.6.2.1 Resistive Sensors 183 8.6.2.2 Capacitive Sensors 184 8.6.2.3 Inductive Sensors 188 8.6.2.4 Resonant Sensors 190 8.7 Issues and Concerns 191 8.7.1 Residual Stresses, CTE Mismatch, and Creep of Thin Films 192 8.7.1.1 Initial Deformation – Residual Stress 192 8.7.1.2 Thermal Deformation – Thermal Expansion Coefficient Mismatch 195 8.7.1.3 Long-time Stability – Creep 197 8.7.2 Quality Factor, Materials Loss, and Temperature Stability 199 8.7.2.1 Anchor Loss 201 8.7.2.2 Thermoelastic Damping (TED) 201 8.7.2.3 Material and Interface Loss 201 8.7.3 Dielectric Charging 203 8.7.4 Nonlinearity and Phase Noise in Oscillators 204 8.8 Concluding Remarks 205 References 207 9 Wafer Transfer 221 Masayoshi Esashi 9.1 Introduction 221 9.2 Film Transfer 223 9.3 Device Transfer (via-last) 228 9.4 Device Transfer (Via-First) 231 9.5 Chip Level Transfer 236 References 241 10 Piezoelectric MEMS 243 T Takeshi Kobayashi (AIST) 10.1 Introduction 243 10.1.1 Fundamental 243 10.1.2 PZT Thin Films Property as an Actuator 244 10.1.3 PZT Thin Film Composition and Orientation 246 10.2 PZT Thin Film Deposition 246 10.2.1 Sputtering 246 10.2.2 Sol–Gel 248 10.2.2.1 Orientation Control 248 10.2.2.2 Thick Film Deposition 249 10.2.3 Electrode Materials and Lifetime of PZT Thin Films 250 10.3 PZT–MEMS Fabrication Process 251 10.3.1 Cantilever and Microscanner 251 10.3.2 Poling 254 References 255 Part III Bonding, Sealing and Interconnection 257 11 Anodic Bonding 259 Masayoshi Esashi 11.1 Principle 259 11.2 Distortion 262 11.3 Influence of Anodic Bonding to Circuits 263 11.4 Anodic Bonding with Various Materials, Structures and Conditions 265 11.4.1 Various Combinations 265 11.4.2 Anodic Bonding with Intermediate Thin Films 269 11.4.3 Variation of Anodic Bonding 271 11.4.4 Glass Reflow Process 274 References 276 12 Direct Bonding 279 Hideki Takagi 12.1 Wafer Direct Bonding 279 12.2 Hydrophilic Wafer Bonding 279 12.3 Surface Activated Bonding at Room Temperature 283 References 286 13 Metal Bonding 289 Joerg Froemel 13.1 Solid Liquid Interdiffusion Bonding (SLID) 290 13.1.1 Au/In and Cu/In 291 13.1.2 Au/Ga and Cu/Ga 294 13.1.3 Au/Sn and Cu/Sn 297 13.1.4 Void Formation 297 13.2 Metal Thermocompression Bonding 298 13.2.1.1 Interface Formation 299 13.2.1.2 Grain Reorientation 299 13.2.1.3 Grain Growth 300 13.3 Eutectic Bonding 301 13.3.1 Au/Si 302 13.3.2 Al/Ge 302 13.3.3 Au/Sn 304 References 304 14 Reactive Bonding 309 Klaus Vogel, Silvia Hertel, Christian Hofmann, Mathias Weiser, Maik Wiemer, Thomas Otto, and Harald Kuhn 14.1 Motivation 309 14.2 Fundamentals of Reactive Bonding 309 14.3 Material Systems 311 14.4 State of the Art 312 14.5 Deposition Concepts of Reactive Material Systems 313 14.5.1 Physical Vapor Deposition 313 14.5.1.1 Conclusion Physical Vapor Deposition and Patterning 315 14.5.2 Electrochemical Deposition of Reactive Material Systems 315 14.5.2.1 Dual Bath Technology 316 14.5.2.2 Single Bath Technology 318 14.5.2.3 Conclusion DBT and SBT 319 14.5.3 Vertical Reactive Material Systems With 1D Periodicity 319 14.5.3.1 Dimensioning 320 14.5.3.2 Fabrication 321 14.5.3.3 Conclusion 323 14.6 Bonding With RMS 323 14.7 Conclusion 326 References 326 15 Polymer Bonding 331 Xiaojing Wang and Frank Niklaus 15.1 Introduction 331 15.2 Materials for Polymer Wafer Bonding 332 15.2.1 Polymer Adhesion Mechanisms 332 15.2.2 Properties of Polymers for Wafer Bonding 335 15.2.3 Polymers Used in Wafer Bonding 337 15.3 Polymer Wafer Bonding Technology 341 15.3.1 Process Parameters in Polymer Wafer Bonding 341 15.3.2 Localized Polymer Wafer Bonding 348 15.4 Precise Wafer-to-Wafer Alignment in Polymer Wafer Bonding 350 15.5 Practical Examples of Polymer Wafer Bonding Processes 351 15.6 Summary and Conclusions 354 References 354 16 Soldering by Local Heating 361 Yu-Ting Cheng and Liwei Lin 16.1 Soldering in MEMS Packaging 361 16.2 Laser Soldering 362 16.3 Resistive Heating and Soldering 365 16.4 Inductive Heating and Soldering 368 16.5 Other Localized Soldering Processes 370 16.5.1 Self-propagative Reaction Heating 370 16.5.2 Ultrasonic Frictional Heating 371 References 374 17 Packaging, Sealing, and Interconnection 377 Masayoshi Esashi 17.1 Wafer Level Packaging 377 17.2 Sealing 378 17.2.1 Reaction Sealing 378 17.2.2 Deposition Sealing (Shell Packaging) 380 17.2.3 Metal Compression Sealing 385 17.3 Interconnection 388 17.3.1 Vertical Feedthrough Interconnection 388 17.3.1.1 Through Glass via (TGV) Interconnection 388 17.3.1.2 Through Si via (TSiV) Interconnection 393 17.3.2 Lateral Feedthrough Interconnection 395 17.3.3 Interconnection by Electroplating 401 References 404 18 Vacuum Packaging 409 Masayoshi Esashi 18.1 Problems of Vacuum Packaging 409 18.2 Vacuum Packaging by Anodic Bonding 409 18.3 Packaging by Anodic Bonding with Controlled Cavity Pressure 414 18.4 Vacuum Packaging by Metal Bonding 416 18.5 Vacuum Packaging by Deposition 417 18.6 Hermeticity Testing 417 References 420 19 Buried Channels in Monolithic Si 423 Kazusuke Maenaka 19.1 Buried Channel/Cavity in LSI and MEMS 423 19.2 Monolithic SON Technology and Related Technologies 425 19.3 Applications of SON 435 References 439 20 Through-substrate Vias 443 Zhyao Wang 20.1 Configurations of TSVs 444 20.1.1 Solid TSVs 444 20.1.2 Hollow TSVs 445 20.1.3 Air-gap TSVs 445 20.2 TSV Applications in MEMS 445 20.2.1 Signal Conduction to the Wafer Backside 446 20.2.2 CMOS-MEMS 3D Integration 446 20.2.3 MEMS and CMOS 2.5D Integration 447 20.2.4 Wafer-level Vacuum Packaging 448 20.2.5 Other Applications 450 20.3 Considerations for TSV in MEMS 450 20.4 Fundamental TSV Fabrication Technologies 450 20.4.1 Deep Hole Etching 451 20.4.1.1 Deep Reactive Ion Etching 451 20.4.1.2 Laser Ablation 452 20.4.2 Insulator Formation 454 20.4.2.1 Silicon Dioxide Insulators 454 20.4.2.2 Polymer Insulators 455 20.4.2.3 Air-gaps 455 20.4.3 Conductor Formation 455 20.4.3.1 Polysilicon 456 20.4.3.2 Single Crystalline Silicon 456 20.4.3.3 Tungsten 457 20.4.3.4 Copper 457 20.4.3.5 Other Conductor Materials 459 20.5 Polysilicon TSVs 460 20.5.1 Solid Polysilicon TSVs 460 20.5.2 Air-gap Polysilicon TSVs 463 20.6 Silicon TSVs 464 20.6.1 Solid Silicon TSVs 465 20.6.2 Air-gap Silicon TSVs 467 20.7 Metal TSVs 469 20.7.1 Solid Metal TSVs 470 20.7.2 Hollow Metal TSVs 474 20.7.3 Air-gap Metal TSVs 480 References 481 Index 493