Table of Contents
Preface xiii
Acknowledgments xv
Chapter 1 MEMS and NEMS Resonator Technologies 1
1.1 What Is MEMS and What Is NEMS? 1
1.2 Physical Fundamentals of MEMS and NEMS Resonators 5
1.2.1 The Mechanical Damped Harmonic Oscillator 6
1.2.2 Quality Factor and Damping Mechanisms 8
1.2.3 Transduction in MEMS and NEMS Resonators 11
1.2.4 Resonance Frequency, Mode Shaping, and Aspect Ratio 18
1.3 Key Fabrication Technologies 22
1.3.1 The Production Cycle 22
1.3.2 Common to Integrated Circuit (MEMS) 24
1.3.3 Nanofabrication Techniques (NEMS) 31
1.4 Summary 33
References 33
Chapter 2 Acoustic Microresonator Technologies 37
2.1 Introduction to Acoustic Wave Resonators 37
2.1.1 Acoustic Waves 38
2.1.2 Acoustic Microresonators 40
2.2 Fundamentals of Piezoelectricity and Acoustic Wave Propagation 42
2.2.1 Theory of Piezoelectricity 42
2.2.2 Excitation and Vibration Mode Description 44
2.3 Surface Acoustic Wave (SAW) Resonators 46
2.3.1 One-Port and Two-Port Configurations 47
2.3.2 SAW Resonator Design 50
2.3.3 SAW Applications 51
2.4 Bulk Acoustic Wave Resonators 51
2.4.1 Acoustic Wave Propagation in BAW Devices 52
2.4.2 Thin-Film Bulk Acoustic Wave Resonators (FBAR) 54
2.4.3 Solidly Mounted Resonators (SMR) 57
2.4.4 FBAR and SMR Applications 60
2.5 Summary 64
References 65
Chapter 3 Design and Modeling of Micro- and Nanoresonators 69
3.1 The Stages of Resonator Design and Modeling 69
3.2 The Electromechanical Transformer 75
3.2.1 MEMS and NEMS Resonators 76
3.2.2 FBAR and Other Acoustic Resonators 78
3.3 Equivalent-Circuit Models 82
3.3.1 The Resonant LC Tank 82
3.3.2 The Butterworth-Van-Dyke Model 83
3.3.3 Case Study: FBAR Process and Modeling 86
3.4 Finite Element Modeling (FEM) 88
3.4.1 Building the Model 90
3.4.2 Structural, Modal, and Harmonic Analyses 92
3.4.3 Coupled-Domain Analysis 94
3.4.4 Case Study: Modal and Harmonic Analysis of a Resonant Mass Sensor 96
3.5 Summary 99
References 100
Chapter 4 Fabrication Techniques 103
4.1 Process Overview 103
4.2 FBAR Fabrication Techniques 105
4.2.1 Oxidation of Silicon 105
4.2.2 Metallization and Piezoelectric Layer Deposition 106
4.2.3 Surface-Micromachining-Based Process 108
4.2.4 Bulk-Micromachining-Based Processes 109
4.3 Instrumentation and Materials for Fabrication 110
4.4 Process Compatibility and Characterization 112
4.4.1 Thin-Film Attributes 112
4.4.2 Crystallography 114
4.4.3 Etching Performance 118
4.4.4 Structural Performance 121
4.5 Summary 123
References 125
Chapter 5 Characterization Techniques 127
5.1 Low- and High-Frequency Electrical Characterization 127
5.1.1 Short-Open DC and Low-Frequency Measurements 128
5.1.2 Microwave Network Theory and the Scattering-Parameter Description 130
5.1.3 High-Frequency Measurement Setup 131
5.1.4 Quality Factor Extraction 133
5.2 Determination of Elastic, Dielectric, and Piezoelectric Constants 140
5.2.1 Elastic Constants 140
5.2.2 Dielectric Constants 143
5.2.3 Piezoelectric Properties 144
5.3 Equivalent-Circuit-Parameter Extraction 146
5.3.1 Parameter-Extraction Algorithm 147
5.3.2 Case Study: Equivalent-Circuit-Parameter Extraction of an FBAR 150
5.4 AFM, Optical, and Electron-Beam-Induced Characterization 151
5.4.1 AFM-Based Characterization with Optical Detection 151
5.4.2 Optical Microscope Interferometry with Piezoelectric Actuation 154
5.4.3 Fabry-Pérot Interferometry 155
5.4.4 Electron-Beam Excitation 157
5.5 Summary 158
References 158
Chapter 6 Performance Optimization 163
6.1 Frequency Stability 163
6.1.1 Thin-Film Thickness Tolerance 164
6.1.2 Layout Design Effects 165
6.1.3 Time and Frequency Stability 165
6.1.4 Temperature Stability and Thermal Coefficient Factor (TCF) 168
6.2 Temperature Compensation 169
6.2.1 TCFBAR Fabrication Processes 170
6.2.2 Behavioral Description and Modeling of a TCFBAR 171
6.3 Frequency Tuning 172
6.3.1 DC Tuning 174
6.3.2 Uniform-Film Deposition 175
6.3.3 FIB-Assisted Tuning Technique 177
6.3.3 Milling of FBAR as Another FIB-Tuning Procedure 179
6.3.4 Frequency-Tuning Sensitivity and Responsivity 180
6.3.5 Quality Factor 181
6.4 Summary 183
References 184
Chapter 7 Integration of Resonator to CMOS Technologies 187
7.1 Integration Strategies 187
7.1.1 Hybrid Integration 188
7.1.2 Monolithic Integration 191
7.1.3 Heterogeneous Integration 194
7.2 State-of-the-Art Integrated Applications 195
7.2.1 MEMS and NEMS Resonators 196
7.2.2 SAW and FBAR 200
7.2.3 Advanced 3D Integration Technologies: Wafer Level Transfer 204
7.3 Wafer-Level-Transfer-Based FBAR-to-CMOS Integration 204
7.3.1 The Resonator Process 207
7.3.2 The CMOS Process 209
7.3.3 The Wafer-Level-Transfer Process 213
7.3.4 Characterization and Technology Optimization 215
7.4 Summary 219
References 221
Chapter 8 Sensor Applications 225
8.1 Resonant Sensing Performance 225
8.1.1 The Role of the Q Factor on Resolution 226
8.1.2 Performance Features and Parameters 227
8.2 Mass Sensors 229
8.2.1 MEMS-Based Microbalances 229
8.2.2 Ultrasensitive NEMS Mass Sensors 234
8.2.3 Acoustic Resonator Distributed-Mass Sensors 238
8.2.4 FBAR-Based Localized-Mass Detection 242
8.3 Mechanical Sensors 245
8.3.1 Pressure Sensors 246
8.3.2 Accelerometers 248
8.4 Atomic Force Detection 251
8.5 Magnetic Sensors 254
8.6 Summary 259
References 260
Chapter 9 Radio Frequency Applications 265
9.1 Introduction 266
9.2 Passive-Circuit Applications 269
9.2.1 SAW, BAW, and FBAR-Based Band-Selection Filters 269
9.2.2 Duplexers, Triplexers, and More 271
9.2.3 Microelectromechanical Filters 277
9.2.4 RF MEMS Switches 282
9.3 Active-Circuit Applications 285
9.3.1 Oscillators 285
9.3.2 Mixers and Mixlers 289
9.3.3 Tuned Low-Noise Amplifiers 292
9.3.4 RF Front-End Systems 293
9.4 Summary 297
References 298
Chapter 10 Case Studies: Modeling, Design, and Fabrication of FBAR and MEMS-Based Systems 303
10.1 Methodological Approach for MEMS-IC Integration 304
10.2 Case I: Compatibility of FBAR and Silicon Technologies 306
10.2.1 Compatibility Testing 306
10.2.2 Front-Side, Reactive-Ion-Etching-Based Process 312
10.2.3 Back-Side Wet-Etching Process 317
10.3 Case II: High-Level Design of a Temperature-Compensated (TC) Oscillator 319
10.3.1 The Temperature Stability Issue in Oscillators 320
10.3.2 Low Phase Noise FBAR-Based Oscillators 322
10.3.3 Codesign of an FBAR-Based TC Oscillator 323
10.4 Case III: Read-Out Circuit Design of a 434-MHz MEMS Resonator 330
10.4.1 MEMS-CMOS Integration Technology 331
10.4.2 Read-Out Circuit Specification and Circuit Architecture 332
10.4.3 Read-Out Implementation and Characterization 333
10.5 Summary 334
References 335
About the Author 337
Index 339
