Piezoelectric MEMS Resonators (eBook)

Harmeet "Mitu" Bhugra lead the development of the world's first PiezoElectric MEMS timing and sensor products at IDT. He holds 22 US patents and has published multiple technical papers and given multiple talks on MEMS technology.Prof. Gianluca Piazza is an Associate Professor in the Electrical and Computer Engineering Department at Carnegie Mellon University.

Preface 5
Contents 8
Contributors 10
Part I Materials for Piezoelectric MEMS Resonators 12
1 AlN Thin Film Processing and Basic Properties 13
1.1 Introduction 13
1.2 Growth of AlN Thin Films by Reactive Magnetron Sputter Deposition 19
1.2.1 Process for c-Axis Textured, Piezoelectric Thin Films 19
1.2.2 The Impact of Substrate Roughness: Film Evolution with Thickness 28
1.2.3 Further Growth Issues: Oxygen Impuritiesand Regrowth Issue 30
1.3 Properties and Characterization 31
1.3.1 Efforts in Ab Initio Calculations 40
1.4 AlN-ScN Alloy Thin Films 40
References 43
2 Lead Zirconate Titanate (PZT) for M/NEMS 48
2.1 PZT Thin Films 48
2.1.1 Deposition 49
2.1.2 Patterning Techniques 55
2.1.3 Device Design Concerns 59
2.1.4 PZT-Based Resonant Devices 62
2.1.5 Summary 73
References 75
3 Gallium Nitride for M/NEMS 81
3.1 Introduction 81
3.1.1 A Bit of History 81
3.1.2 GaN Technology Enabling MEMS 82
3.1.3 Benefits of GaN 83
3.2 Transduction Mechanisms in Resonant GaN Devices 85
3.2.1 Passive Piezoelectric Transduction 85
Passive Piezoelectric GaN Resonators with Top and Bottom Electrodes 85
Lateral Excitation of GaN Resonators 86
Metal-Free Transduction with 2DEG 88
3.2.2 Piezoresistive Transduction 88
3.2.3 GaN Resonant Body Transistors 91
Transistor Sensing in Piezoelectric Resonators 92
Flexural Resonant Body Transistors 93
Bulk Wave Resonant Body Transistors 93
3.3 Applications 94
3.3.1 GAN-Based Physical Resonant Sensors 94
3.3.2 Frequency Synthesizers and Timing 97
3.4 Future Outlook 98
References 102
4 Lithium Niobate for M/NEMS Resonators 107
4.1 Historical Development of Lithium Niobate Material and Thin Films 108
4.2 Material Properties of Lithium Niobate 111
4.3 Bulk Acoustic Modes in Lithium Niobate Thin Films 113
4.4 Micromachining Lithium Niobate Thin Films 119
4.5 Design and Performance of Lithium Niobate Devices 126
4.6 Discussion and Potential Applications of LithiumNiobate Devices 131
References 133
Part II Design of Piezoelectric MEMS Resonators 138
5 Quality Factor and Coupling in Piezoelectric MEMS Resonators 139
5.1 Introduction 139
5.2 Quality Factor 139
5.2.1 Sources of Loss 141
Intrinsic Losses 142
Extrinsic Losses 146
5.2.2 Discussion on Loss 149
5.3 Coupling Factor 150
5.3.1 Piezoelectric Coupling Factor 150
5.3.2 Effective Electromechanical Coupling Factor 151
5.3.3 Discussion on Coupling Factor 153
5.4 Conclusion (Figure of Merit) 154
References 154
6 Flexural Piezoelectric Resonators 159
6.1 Introduction 159
6.2 Mechanics of Laminates 159
6.2.1 Natural Frequencies 161
6.2.2 Thin-Film Piezo-Coefficient 161
6.3 Vibration Analysis via Energy Methods 162
6.4 One-Dimensional Resonators 164
6.4.1 Clamped-Clamped Bean Analysis 166
6.4.2 Natural Frequencies 168
6.4.3 Two-Port Resonators 168
6.5 Two-Dimensional Resonators 170
6.5.1 Square Plates 171
6.5.2 Round Plates 174
6.5.3 7 Example – Predicting Coupling to Multiple Vibration Modes 176
References 178
7 Laterally Vibrating Piezoelectric MEMS Resonators 180
7.1 Introduction 180
7.2 Operating Principle 181
7.3 Materials 188
7.4 Frequency Scaling 190
7.5 Fabrication Techniques 191
7.6 Examples of Demonstrated Prototypes 193
References 202
8 BAW Piezoelectric Resonators 208
8.1 Introduction 208
8.2 BVD Model 209
8.3 Mason's Equivalent Circuit Model 214
8.4 Resonator Structures 217
8.5 Material Choice 219
8.6 Lateral Wave Propagation 220
8.7 Summary 223
References 223
9 Shear Piezoelectric MEMS Resonators 226
9.1 Introduction to MEMS Resonators 226
9.2 Piezoelectric Shear Modes 228
9.3 Piezoelectric Thickness-Shear Principles 228
9.4 Quartz Crystal Cut Angles 232
9.5 Frequency Dependence on Plate Dimensions 233
9.6 Thickness-Shear-Mode Simulation 234
9.7 Frequency Dependence on Temperature 235
9.8 The Equivalent Circuit 237
9.9 Fabrication of Thickness-Shear Devices 240
9.10 Examples of Prototype Devices 242
9.11 Future Development 246
9.12 Summary 246
References 247
10 Temperature Compensation of Piezo-MEMS Resonators 248
10.1 Introduction 248
10.2 Temperature Sensitivity of Resonance Frequency 249
10.3 Passive Compensation Techniques 250
10.3.1 Compensation by Resonator Composition Design 250
10.3.2 Compensation by Material Properties Engineering 253
10.3.3 Other Passive Compensation Techniques 256
10.4 Active Compensation Techniques 257
References 260
11 Computational Modeling Challenges 262
11.1 Introduction 262
11.2 Challenges in Computing the Frequency Response 263
11.2.1 Motivation 263
11.2.2 Computing the Frequency Response 265
11.3 Modeling Energy Loss Mechanisms 270
11.3.1 Anchor Loss 271
11.3.2 Thermoelastic Dissipation 274
11.3.3 Fluid Damping 276
11.4 Static and Dynamic Nonlinearity 278
11.4.1 Residual Stress 279
11.4.2 Nonlinearity from High Power 280
11.5 Conclusion 281
References 281
Part III Manufacturing and Reliability of Piezoelectric MEMS Resonators 285
12 Fabrication Process Flows for Implementation of Piezoelectric MEMS Resonators 286
12.1 Introduction 287
12.2 Deposition of Piezoelectric AlN 288
12.3 Fabrication Process Flow of Piezo-Only Resonators 291
12.4 Fabrication Process Flow of Piezo-on-Substrate Resonators 292
12.5 Sidewall AlN Process for 3D Transduction of MEMS Resonators 295
12.6 Fabrication Process Flow for AlGaN/GaN Resonators with Integrated HEMT Read-Out 297
References 299
13 Reliability and Quality Assessment (Stability and Packages) 302
13.1 A Long and Demanding History Sets the Demands for the Resonators 302
13.2 The Challenges of FCP Devices: Longevity and Critical Applications Are Common 303
13.3 Where Did the Rules of Evaluation Come from? 304
13.4 The Challenges of an IC and Electromechanical Device 304
13.5 With FCP Long History, So Much Is a Level of Expectation 305
13.6 US Military Standards 306
13.7 JEDEC Standards 307
13.8 Other Standards 307
13.9 In-Process and Production Monitoring 308
13.10 Other Specifications for Frequency Control Products 309
13.10.1 Response to Temperature Change 309
13.10.2 Perturbations 309
13.10.3 Power Supply Noise Sensitivity 309
13.10.4 System-Injected Noise 310
13.10.5 Low-Frequency Wander 310
13.10.6 Long-Term Aging 310
13.10.7 EMI Radiation 312
13.11 What Are the Expectations of the Future? 312
13.11.1 The Device Sizes 312
13.11.2 The Device Supply Voltages and Power 312
13.11.3 The Device Cost 313
13.11.4 Self-Test 313
14 Large Volume Testing and Calibration 314
14.1 Purpose of Testing in Manufacturing 316
14.2 Considerations in Testing in Manufacturing 316
14.3 Forming a Testing Strategy 317
14.4 Methods of Rejection 318
14.4.1 Electrical Rejections 318
Resonance Check 318
Spec Limits Rejection 319
Dynamic Spec Limits Rejection 320
Yield Limit Rejection 321
Geographical Rejection Including Expansion 322
Rejection by Electrical Signature 322
Rejection Beyond Resonance Parameters 324
14.4.2 Visual Rejections 324
Seal Defect Rejection 324
Delaminated Cap Rejection 325
Bond Void Rejection 326
Edge Die Rejection 327
Delaminated Metal Pad Rejection 327
14.5 Test and Rejection Analyses Flow 328
14.6 Consideration in Test Implementation 328
14.6.1 Defect Coding System 328
14.6.2 Interface Design for Test Programs 329
14.6.3 Calibration of Prober Setup 330
14.6.4 Data Processing and Automation 330
14.7 Test Time Reduction 331
14.7.1 Multi-site Testing 331
14.7.2 Test Program Optimization 332
14.7.3 Hardware or Software 332
14.7.4 Data File Formats 333
14.8 Calibration 333
14.9 Conclusion 334
References 334
Part IV Real World Implementations 335
15 High Frequency Oscillators for Mobile Devices 336
15.1 Understanding the Diversity of Timing Requirements in Mobile Devices 339
15.2 Significance of Acoustic Devices 341
15.2.1 The Significance of Resonator Q 341
15.2.2 What Is Preventing Us Today From Using an Integrated Circuit Solution to Provide Time and Frequency 343
15.3 Phase Noise in Oscillators 343
15.4 Historical Developments of the Sand 9 Piezoelectric MEMS Resonator 347
15.4.1 Early Prototypes 349
15.4.2 A Chip-Scale Package VC-TCXO Replacement Using Piezoelectric MEMS Resonators 350
15.4.3 Piezoelectric MEMS Concept for a 125 MHz VC-TCXO 357
15.5 Integrated MEMS Resonator 367
15.5.1 Integrated Cellular Transceiver 369
15.6 Results 371
15.7 Understanding the MEMS Timing Business 373
15.8 The Business Case for MEMS Cellular Timing Devices 376
15.9 Where Are We Today? 379
15.9.1 When Is the MEMS Timing Revolution Going to Happen? 380
15.9.2 How to Imitate a Xtal with an LLQ? 380
15.10 The Value of MEMS Timing 382
15.11 Conclusions 382
References 384
16 BAW Filters and Duplexers for Mobile Communication 387
16.1 Introduction 387
16.2 Short History of BAW 388
16.3 Types of Filters Used in Smartphones 390
16.4 Evolution of Size and Performance 392
16.5 Insertion Loss 394
16.6 Port Impedance and Matching 395
16.7 Rejection and Isolation 399
16.8 Power Handling and Reliability 402
16.9 Temperature Effects 404
16.10 Group Delay 405
16.11 Linearity of Filters and Duplexers 406
16.12 Packaging and RF Module Integration 407
16.13 Filter Design Methodology 409
16.14 Solutions for Carrier Aggregation in Long-Term Evolution (LTE) 412
References 413
Index 414