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
