RF MEMS and Their Applications

Vijay K. Varadan, K. A. Jose, Udo Zoelzer, K. J. Vinoy9780470843086, 047084308X

The growing requirement for wireless devices with increased functionality and reduced power consumption is driving the development of new RF micro-electro-mechanical systems (RF MEMS).RF MEMS and their Applications sets out to address an increasing need for information by providing a vital overview of this emerging field.This book:* Presents an accessible review of MEMS devices and fabrication techniques.* Discusses the development of RF MEMS switches and the attempts to reduce their actuation voltage.* Outlines the design and development of RF MEMS based inductors, capacitors, filters and phase shifters.* Covers the technology behind micromachined antennas.* Describes integration and packaging techniques for RF MEMS devices.Offering readers a guide to the development of RF MEMS components and systems, this unique reference will appeal to RF and microwave engineers and MEMS experts alike. Graduate students and researchers in the telecommunications and microelectronics field will profit from the detailed overview of current microfabrication techniques. Materials technologists and physicists working in industrial and academic research & development will also find this a valuable reference.

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Table of contents :
TeamLiB……Page 1
Cover……Page 2
Contents……Page 7
Preface……Page 13
1.1 INTRODUCTION……Page 15
1.2 MEMS……Page 16
1.3.1 Bulk micromachining of silicon……Page 19
1.3.2 Surface micromachining of silicon……Page 22
1.3.3 Wafer bonding for MEMS……Page 23
1.3.4 LIGA process……Page 25
1.3.5 Micromachining of polymeric MEMS devices……Page 27
1.3.6 Three- dimensional microfabrications……Page 29
1.4 ELECTROMECHANICAL TRANSDUCERS……Page 30
1.4.1 Piezoelectric transducers……Page 32
1.4.2 Electrostrictive transducers……Page 34
1.4.3 Magnetostrictive transducers……Page 36
1.4.4 Electrostatic actuators……Page 38
1.4.5 Electromagnetic transducers……Page 41
1.4.6 Electrodynamic transducers……Page 43
1.4.7 Electrothermal actuators……Page 46
1.4.8 Comparison of electromechanical actuation schemes……Page 48
1.5.1 Piezoresistive sensing……Page 49
1.5.3 Piezoelectric sensing……Page 51
1.5.5 Surface acoustic wave sensors……Page 52
1.6.2 Polymers for MEMS……Page 56
1.7 SCOPE OF THIS BOOK……Page 58
REFERENCES……Page 59
2.1.1 Evaporation……Page 65
2.1.2 Sputtering……Page 67
2.2.1 Electrical and chemical properties……Page 68
2.2.2 Growth and deposition……Page 71
2.3.1 Oxide . lm formation by thermal oxidation……Page 75
2.3.2 Deposition of silicon dioxide and silicon nitride……Page 76
2.3.4 Ferroelectric thin . lms……Page 78
2.4.1 Classi . cation of polymers……Page 81
2.4.2 UV radiation curing……Page 88
2.4.3 SU- 8 for polymer MEMS……Page 94
2.5.1 Isotropic and orientation- dependent wet etching……Page 98
2.5.3 Buried oxide process……Page 102
2.5.4 Silicon fusion bonding……Page 103
2.5.5 Anodic bonding……Page 104
2.6.1 Sacri . cial layer technology……Page 105
2.6.2 Material systems in sacri . cial layer technology……Page 106
2.6.3 Surface micromachining using plasma etching……Page 107
2.7 MICROSTEREOLITHOGRAPHY FOR POLYMER MEMS……Page 108
2.7.1 Scanning method……Page 109
2.7.2 Two- photon microstereolithography……Page 110
2.7.4 Projection method……Page 111
2.7.5 Polymeric MEMS architecture with silicon, metal and ceramics……Page 116
REFERENCES……Page 119
3.1 INTRODUCTION……Page 123
3.2 SWITCH PARAMETERS……Page 125
Switching transients……Page 126
Insertion loss……Page 127
Resonant frequency……Page 128
3.3 BASICS OF SWITCHING……Page 129
3.3.1 Mechanical switches……Page 130
3.4 SWITCHES FOR RF AND MICROWAVE APPLICATIONS……Page 131
3.4.1 Mechanical RF switches……Page 132
3.4.2 PIN diode RF switches……Page 133
3.4.3 Metal oxide semiconductor . eld effect transistors and monolithic microwave integrated circuits……Page 137
3.4.4 RF MEMS switches……Page 138
3.4.5 Integration and biasing issues for RF switches……Page 139
3.5 ACTUATION MECHANISMS FOR MEMS DEVICES……Page 141
3.5.1 Electrostatic switching……Page 142
3.5.2 Approaches for low- actuation- voltage switches……Page 155
3.5.3 Mercury contact switches……Page 160
3.5.5 Electromagnetic switching……Page 162
3.5.6 Thermal switching……Page 165
3.6.1 Magnetic actuation in micro relays……Page 166
3.6.2 Relay contact force and materials……Page 170
3.7 DYNAMICS OF THE SWITCH OPERATION……Page 171
3.7.1 Switching time and dynamic response……Page 172
3.7.2 Threshold voltage……Page 174
3.8 MEMS SWITCH DESIGN, MODELING AND EVALUATION……Page 176
3.8.1 Electromechanical . nite element analysis……Page 177
3.8.2 RF design……Page 179
3.9 MEMS SWITCH DESIGN CONSIDERATIONS……Page 188
3.10 CONCLUSIONS……Page 189
REFERENCES……Page 192
4.1 INTRODUCTION……Page 197
4.3 MEMS INDUCTORS……Page 198
4.3.1 Self- inductance and mutual inductance……Page 199
4.3.2 Micromachined inductors……Page 202
4.3.3 Effect of inductor layout……Page 208
4.3.4 Reduction of stray capacitance of planar inductors……Page 212
4.3.5 Approaches for improving the quality factor……Page 214
4.3.6 Folded inductors……Page 225
4.3.7 Modeling and design issues of planar inductors……Page 226
4.4 MEMS CAPACITORS……Page 229
4.4.1 MEMS gap- tuning capacitors……Page 231
4.4.2 MEMS area- tuning capacitors……Page 238
4.4.3 Dielectric tunable capacitors……Page 242
4.5 CONCLUSIONS……Page 243
REFERENCES……Page 249
5.1 INTRODUCTION……Page 255
5.2.1 Modeling of resonators……Page 258
5.2.2 Mechanical coupling components……Page 265
5.2.3 General considerations for mechanical . lters……Page 271
5.3.1 Electrostatic comb drive……Page 272
5.3.2 Micromechanical . lters using comb drives……Page 274
5.3.3 Micromechanical . lters using electrostatic coupled beam structures……Page 279
5.4 SURFACE ACOUSTIC WAVE FILTERS……Page 282
5.4.1 Basics of surface acoustic wave . lter operation……Page 283
5.4.2 Wave propagation in piezoelectric substrates……Page 284
5.4.3 Design of interdigital transducers……Page 285
5.4.4 Single- phase unidirectional transducers……Page 288
5.4.5 Surface acoustic wave devices: capabilities, limitations and applications……Page 289
5.5 BULK ACOUSTIC WAVE FILTERS……Page 290
5.6 MICROMACHINED FILTERS FOR MILLIMETER WAVE FREQUENCIES……Page 292
5.7 SUMMARY……Page 296
REFERENCES……Page 297
6.1 INTRODUCTION……Page 299
6.2 TYPES OF PHASE SHIFTERS AND THEIR LIMITATIONS……Page 300
6.2.2 Semiconductor phase shifters……Page 301
6.2.4 Limitations of phase shifters……Page 302
6.3.2 Distributed MEMS phase shifters……Page 303
6.3.3 Polymer- based phase shifters……Page 310
6.4 FERROELECTRIC PHASE SHIFTERS……Page 312
6.4.1 Distributed parallel plate capacitors……Page 313
6.4.2 Bilateral interdigital phase shifters……Page 315
6.4.3 Interdigital capacitor phase shifters……Page 318
6.6 CONCLUSIONS……Page 319
REFERENCES……Page 320
7.1 INTRODUCTION……Page 323
7.2 MICROMACHINED TRANSMISSION LINES……Page 324
7.2.1 Losses in transmission lines……Page 325
7.2.2 Co- planar transmission lines……Page 327
7.2.3 Microshield and membrane- supported transmission lines……Page 330
7.2.4 Microshield circuit components……Page 335
7.2.5 Micromachined waveguide components……Page 338
7.2.7 Micromachined mixer……Page 341
7.2.8 Passive components: resonators and . lters……Page 344
7.2.9 Micromachined antennas……Page 346
7.3 DESIGN, FABRICATION AND MEASUREMENT……Page 348
7.3.3 Evaluation……Page 349
7.4 CONCLUSIONS……Page 351
REFERENCES……Page 352
8.1 INTRODUCTION……Page 357
8.2.1 Basic characteristics of microstrip antennas……Page 358
8.2.2 Design parameters of microstrip antennas……Page 361
8.3 MICROMACHINING TECHNIQUES TO IMPROVE ANTENNA PERFORMANCE……Page 365
8.4 MICROMACHINING AS A FABRICATION PROCESS FOR SMALL ANTENNAS……Page 370
8.5 MICROMACHINED RECONFIGURABLE ANTENNAS……Page 374
8.6 SUMMARY……Page 376
REFERENCES……Page 377
9.1 INTRODUCTION……Page 379
9.2.1 Mechanical support……Page 380
9.3 TYPES OF MEMS PACKAGES……Page 381
9.3.3 Plastic packages……Page 382
9.3.5 Embedded overlay……Page 383
9.3.6 Wafer- level packaging……Page 384
9.3.7 Microshielding and self- packaging……Page 386
9.4 FLIP- CHIP ASSEMBLY……Page 387
9.5 MULTICHIP MODULE PACKAGING……Page 389
9.5.1 Wafer bonding……Page 391
9.6.2 Integration of MEMS devices with microelectronics……Page 394
9.6.4 Reliability and key failure mechanisms……Page 396
9.8 CONCLUSIONS……Page 397
REFERENCES……Page 398
Index……Page 401