本书全面论述了微机电系统（MEMS）的基础知识，涵盖了MEMS技术的主要方面，同时引用了经典的MEMS研究论文和前沿的研究论文，为学生深入学习MEMS技术提供了指引。书中提炼出了四个典型的传感器实例：惯性传感器、压力传感器、流量传感器和触觉传感器，并介绍了利用不同原理、材料和工艺制造这些传感器的方法，既便于比较，又可以启发学生的创新意识并提高创新能力。

微机电系统基础
Chang Liu（刘昶） 美国西北大学工程学院终身教授。他领导的西北大学 MEDX实验室主要的科研方向为传感器、仿生传感器、微机电系统和纳米加工技术、流体传感器、触觉传感器及各种传感器的应用。他同时也是西北大学超净加工（cleanroom）NuFab的主任。 他于1996年在美国加州理工学院电机系获得博士学位，是中国大陆地区留美学习微机电系统并在美国大学担任教授职位的第一人。之后他一直在美国从事微机电系统和传感器方面的科研和教学工作。加入西北大学前，刘昶还曾任教于美国伊利诺伊大学香槟分校并获终身教职（1996－2007）。赴美前他曾就读于中国北京清华大学精密仪器系。
作者简介
本书全面论述了微机电系统（MEMS）的基础知识，涵盖了MEMS技术的主要方面，同时引用了经典的MEMS研究论文和前沿的技术论文，为学生深入学习MEMS技术提供了指引。书中提炼出了四个典型的传感器实例：惯性传感器、压力传感器、流量传感器和触觉传感器，并介绍了利用不同原理、材料和工艺制造这些传感器的方法，既便于比较，又可以启发学生的创新意识并提高创新能力。
本书被美国斯坦福大学、伊利诺伊大学等选为教材。
本版的改进主要包括：
加强对MEMS设计、制造和材料问题的讨论。
根据新的进展，更新了相关内容。
增加了习题，更新了实例和插图，使第2版内容更加丰富。
提供配套的资源网站（http://www.memscentral.com），为读者提供补充阅读材料、补充教学材料、与MEMS领域相关的网址资源以及勘误表。

Five years have passed since the first edition of this book was published. Over the five years,

the world has witnessed a technological revolution headlined by an array of exciting consumer and
industrial products such as the Nintendo Wii, Apple iPod/iPad, sensor-rich smart phones,
phones with cameras, new operating systems for mobile phones and apps, e-books, WiFi, voice-
over-IP calls, social networking, 3D animated movies, and cloud computing, to name the major
ones that affect everyday living. These new entries were practically nonexistent in the main
stream when the first edition of this book was published in 2005. World news in 2010 is dominated

by such themes as alternative energy, scarcity of resources, manufacturing outsourcing,
budget and credit crisis, economic growth in some parts of the world, and reforms in financial
management, health care, and education.
This book has been warmly welcomed since its first edition. It is adapted in over 50 universities

world wide, and has been translated into three international editions (simplified Chinese,
traditional Chinese, and Korean). In preparing for the second edition, I am very encouraged by
feedback from editors, students, and teachers who use this book. The objectives of the second
edition are the following:
1. To strengthen the book’s discussion about MEMS design, processing, and materials.
2. To update course materials by including new insights and new developments. Many changes
have happened in the MEMS field. New ideas, new capabilities, and new case studies of
product successes are available today. This book reflects these new trends in development.
3. To enrich this book by providing new homework problems, updated examples, figures, etc.
4. To correct known mistakes.
5. To provide an enduring infrastructure to support teaching activities and MEMS education to a

broader audience.
Readers will find the following major update features:
New contents, concepts, and insight. The MEMS field has changed dramatically in the past five
years. This book captures new contents (generated in academia and industry), new concepts
(e.g., packaging and integration), and insights. This should provide more value for the reader.
New homework problems. New homework problems have been added to facilitate teaching
and student learning. Homework solutions can be provided to teachers upon request.
Added analytical examples for design and process selection. This new edition provides
teachers with new materials to discuss design and process analytically.
New beginner-friendly materials for teaching processes. Beginning students may be amazed
by the array of processing-related information.A number of new tables are provided to make it
easier for students to climb the learning curve. These tables (in the appendix section) provide
first-time students a simplified summary of the most commonly encountered materials and
etching methods. An easy-to-understand table summarizing their interactions is also provided.
Deeper case studies added to challenge the readers understanding about the subject. The
overall structural of the book is maintained. A new chapter (Chapter 15) is added, dealing with
in-depth case discussion of successful MEMS products in the market place. I believe these
commercialized MEMS devices, conceived for and tested in the real-life business world, are
good examples to illustrate principles of design, fabrication, and integration. A discussion of
most essential fabrication technology is added in Chapter 2. The discussion is meant to provide
essential and qualitative review of processing methods. Other changes can be found in various
chapters, especially Chapters 1, 2, and 12.
A new dedicated companion Web site for teachers and students. The Web site is a permanent
home to the book and will serve the readers of this book in the new era of internet and online
communication. On this Web site, a reader can find supplemental chapters, supplemental
teaching materials, links to resources pertaining to the MEMS field, and errata. Teachers will
find teaching aid materials such as PowerPoint files, figures, homework solutions, etc. The Web
site serves a number of important purposes. It is originally driven by the desire to not make

this book too large while still maintain its ability to satisfy a varied audience. It will help

the user community in a way that is more enduring than a single print.
The Web site dedicated to this book is www.memscentral.com.
Student and instructor resources for the International Edition are available at www.
pearsoninternationaleditions.com/liu
Chapter line-up and flow is streamlined. The chapter on optical MEMS is now moved to the
Web site as a supplement. This and other chapters dealing with specialty topics (such as RF
MEMS, BioMEMS) will be hosted in the Web site so that I can keep the book small and still
satisfy the needs of teachers who wish to discuss about these exciting areas in class. Moving the
chapters to the Web site also makes it possible to update frequently.
May the MEMS field continue to grow! I hope you enjoy reading and using this book.

CHANG LIU
Evanston, IL
September 2010

工程机械

本书全面论述了微机电系统（MEMS）的基础知识，涵盖了MEMS技术的主要方面，同时引用了经典的MEMS研究论文和前沿的技术论文，为学生深入学习MEMS技术提供了指引。书中提炼出了四个典型的传感器实例：惯性传感器、压力传感器、流量传感器和触觉传感器，并介绍了利用不同原理、材料和工艺制造这些传感器的方法，既便于比较，又可以启发学生的创新意识并提高创新能力。
本书被美国斯坦福大学、伊利诺伊大学等选为教材。
本版的改进主要包括：
 加强对MEMS设计、制造和材料问题的讨论。
 根据新的进展，更新了相关内容。
 增加了习题，更新了实例和插图，使第2版内容更加丰富。
 提供配套的资源网站（http://www.memscentral.com），为读者提供补充阅读材料、补充教学材料、与MEMS领域相关的网址资源以及勘误表。

(美)Chang Liu(刘昶) 著　　　　　　　　　　　　　　　　西北大学：Chang Liu（刘昶） 美国西北大学工程学院终身教授。他领导的西北大学 MEDX实验室主要的科研方向为传感器、仿生传感器、微机电系统(MEMS)和纳米加工技术、流体传感器、触觉传感器及各种传感器的应用。他同时也是西北大学超净加工（cleanroom）NuFab的主任。 他于1996年在美国加州理工学院电机系获得博士学位，是中国大陆地区留美学习微机电系统并在美国大学担任教授职位的第一人。之后他一直在美国从事微机电系统和传感器方面的科研和教学工作。加入西北大学前，刘昶还曾任教于美国伊利诺伊大学香槟分校并获终身教职（1996－2007）。赴美前他曾就读于中国北京清华大学精密仪器系。

PREFACE 3
A NOTE TO INSTRUCTORS 5
NOTATIONAL CONVENTIONS 7
Chapter 1 Introduction 15
1.0 Preview 15
1.1 The History of MEMS Development 15
1.1.1 From the Beginning to 1990 15
1.1.2 From 1990 to 2001 19
1.1.3 2002 to Present 25
1.1.4 Future Trends 26
1.2 The Intrinsic Characteristics of MEMS 27
1.2.1 Miniaturization 27
1.2.2 Microelectronics Integration 29
1.2.3 Parallel Fabrication with Precision 29
1.3 Devices: Sensors and Actuators 30
1.3.1 Energy Domains and Transducers 30
1.3.2 Sensors Considerations 32
13.3 Sensor Noise and Design Complexity 34
1.3.4 Actuators Considerations 35
Summary 36
Problems 37
References 41
Chapter 2 First-Pass Introduction to Microfabrication 47
2.0 Preview 47
2.1 Overview of Microfabrication 47
2.2 Essential Overview of Frequently Used Microfabrication Processes 51
2.2.1 Photolithography 51
2.2.2 Thin Film Deposition 51
2.2.3 Thermal Oxidation of Silicon 55
2.2.4 Wet Etching 55
2.2.5 Silicon Anisotropic Etching 57
2.2.6 Plasma Etching and Reactive Ion Etching 57
2.2.7 Doping 58
2.2.8 Wafer Dicing 59
2.2.9 Wafer Bonding 60
2.3 The Microelectronics Fabrication Process Flow 61
2.4 Silicon-Based MEMS Processes 63
2.5 Packaging and Integration 69
2.5.1 Integration Options 69
2.5.2 Encapsulation 71
2.6 New Materials and Fabrication Processes 71
2.7 Process Selection and Design 73
2.7.1 Points of Consideration for Deposition Processes 73
2.7.2 Points of Consideration for Etching Processes 73
2.7.3 Ideal Rules for Building a Process Flow 75
2.7.4 Rules for Building a Robust Process 75
Summary 77
Problems 77
References 79
Chapter 3 Review of Essential Electrical and Mechanical Concepts 84
3.0 Preview 84
3.1 Conductivity of Semiconductors 85
3.1.1 Semiconductor Materials 85
3.1.2 Calculation of Charge Carrier Concentration 86
3.1.3 Conductivity and Resistivity 89
3.2 Crystal Planes and Orientations 93
3.3 Stress and Strain 96
3.3.1 Internal Force Analysis: Newton’s Laws of Motion 96
3.3.2 Definitions of Stress and Strain 98
3.3.3 General Scalar Relation Between Tensile Stress and Strain 101
3.3.4 Mechanical Properties of Silicon and Related Thin Films 103
3.3.5 General Stress—Strain Relations 105
3.4 Flexural Beam Bending Analysis Under Simple Loading Conditions 107
3.4.1 Types of Beams 108
3.4.2 Longitudinal Strain Under Pure Bending 110
3.4.3 Deflection of Beams 112
3.4.4 Finding the Spring Constants 113
3.5 Torsional Deflections 118
3.6 Intrinsic Stress 120
3.7 Dynamic System, Resonant Frequency, and Quality Factor 125
3.7.1 Dynamic System and Governing Equation 125
3.7.2 Response Under Sinusoidal Resonant Input 126
3.7.3 Damping and Quality Factor 128
3.7.4 Resonant Frequency and Bandwidth 128
3.8 Active Tuning of Spring Constant and Resonant Frequency 129
3.9 A List of Suggested Courses and Books 130
Summary 131
Problems 132
References 136
Chapter 4 Electrostatic Sensing and Actuation 141
4.0 Preview 141
4.1 Introduction to Electrostatic Sensors and Actuators 141
4.2 Parallel-Plate Capacitor 143
4.2.1 Capacitance of Parallel Plates 143
4.2.2 Equilibrium Position of Electrostatic Actuator under Bias 146
4.2.3 Pull-in Effect of Parallel-Plate Actuators 149
4.3 Applications of Parallel-Plate Capacitors 154
4.3.1 Inertia Sensor 155
4.3.2 Pressure Sensor 160
4.3.3 Flow Sensor 165
4.3.4 Tactile Sensor 168
4.3.5 Parallel-Plate Actuators 170
4.4 Interdigitated Finger Capacitors 171
4.5 Applications of Comb-Drive Devices 176
4.5.1 Inertia Sensors 176
4.5.2 Actuators 180
Summary 182
Problems 182
References 186
Chapter 5 Thermal Sensing and Actuation 190
5.0 Preview 190
5.1 Introduction 190
5.1.1 Thermal Sensors 190
5.1.2 Thermal Actuators 191
5.1.3 Fundamentals of Thermal Transfer 191
5.2 Sensors and Actuators Based on Thermal Expansion 196
5.2.1 Thermal Bimorph Principle 198
5.2.2 Thermal Actuators with a Single Material 205
5.3 Thermal Couples 207
5.4 Thermal Resistors 210
5.5 Applications 212
5.5.1 Inertia Sensors 213
5.5.2 Flow Sensors 215
5.5.3 Infrared Sensors 228
5.5.4 Other Sensors 231
Summary 236
Problems 236
References 241
Chapter 6 Piezoresistive Sensors 245
6.0 Preview 245
6.1 Origin and Expression of Piezoresistivity 245
6.2 Piezoresistive Sensor Materials 248
6.2.1 Metal Strain Gauges 248
6.2.2 Single Crystal Silicon 249
6.2.3 Polycrystalline Silicon 252
6.3 Stress Analysis of Mechanical Elements 252
6.3.1 Stress in Flexural Cantilevers 252
6.3.2 Stress and Deformation in Membrane 258
6.4 Applications of Piezoresistive Sensors 260
6.4.1 Inertial Sensors 260
6.4.2 Pressure Sensors 266
6.4.3 Tactile Sensor 268
6.4.4 Flow Sensor 271
Summary 276
Problems 277
References 281
Chapter 7 Piezoelectric Sensing and Actuation 283
7.0 Preview 283
7.1 Introduction 283
7.1.1 Background 283
7.1.2 Mathematical Description of Piezoelectric Effects 285
7.1.3 Cantilever Piezoelectric Actuator Model 287
7.2 Properties of Piezoelectric Materials 290
7.2.1 Quartz 290
7.2.2 PZT 292
7.2.3 PVDF 293
7.2.4 ZnO 294
7.2.5 Other Materials 298
7.3 Applications 299
7.3.1 Inertia Sensors 299
7.3.2 Acoustic Sensors 303
7.3.3 Tactile Sensors 306
7.3.4 Flow Sensors 307
7.3.5 Surface Elastic Waves 309
Summary 311
Problems 311
References 315
Chapter 8 Magnetic Actuation 317
8.0 Preview 317
8.1 Essential Concepts and Principles 317
8.1.1 Magnetization and Nomenclatures 317
8.1.3 Selected Principles of Micro Magnetic Actuators 321
8.2 Fabrication of Micro Magnetic Components 326
8.2.1 Deposition of Magnetic Materials 326
8.2.2 Design and Fabrication of Magnetic Coil 328
8.3 Case Studies of MEMS Magnetic Actuators 331
Summary 342
Problems 342
References 344
Chapter 9 Summary of Sensing and Actuation Methods 346
9.0 Preview 346
9.1 Comparison of Major Sensing and Actuation Methods 346
9.2 Other Sensing and Actuation Methods 348
9.2.1 Tunneling Sensing 348
9.2.3 Optical Sensing 350
9.2.4 Field Effect Transistors 356
9.2.5 Radio Frequency Resonance Sensing 359
Summary 360
Problems 361
References 362
Chapter 10 Bulk Micromachining and Silicon Anisotropic Etching 365
10.0 Preview 365
10.1 Introduction 365
10.2 Anisotropic Wet Etching 367
10.2.1 Introduction 367
10.2.2 Rules of Anisotropic Etching—Simplest Case 367
10.2.3 Rules of Anisotropic Etching—Complex Structures 373
10.2.4 Forming Protrusions 381
10.2.5 Interaction of Etching Profiles from Isolated Patterns 381
10.2.6 Summary of Design Methodology 383
10.2.7 Chemicals for Wet Anisotropic Etching 385
10.3 Dry Etching and Deep Reactive Ion Etching 390
10.4 Isotropic Wet Etching 391
10.5 Gas Phase Etchants 391
10.6 Native Oxide 392
10.7 Special Wafers and Techniques 393
Summary 393
Problems 394
References 400
Chapter 11 Surface Micromachining 403
11.0 Preview 403
11.1 Basic Surface Micromachining Processes 403
11.1.1 Sacrificial Etching Process 403
11.1.2 Micro Motor Fabrication Process—A First Pass 404
11.2.3 Micro Motor Fabrication Process—A Second Pass 405
11.1.4 Micro Motor Fabrication Process—Third Pass 406
11.2 Structural and Sacrificial Materials 409
11.2.1 Material Selection Criteria for a Two-layer Process 409
11.2.2 Thin Films by Low Pressure Chemical Vapor Deposition 410
11.2.3 Other Surface Micromachining Materials and Processes 413
11.3 Acceleration of Sacrificial Etch 414
11.4 Stiction and Anti-stiction Methods 416
Summary 417
Problems 418
References 420
Chapter 12 Process Synthesis: Putting It All Together 424
12.0 Preview 424
12.1 Process for Suspension Beams 426
12.2 Process for Membranes 432
12.3 Process for Cantilevers 437
12.3.1 SPM Technologies Case Motivation 437
12.3.2 General Fabrication Methods for Tips 439
12.3.3 Cantilevers with Integrated Tips 441
12.3.4 Cantilevers with Integrated Sensors 446
12.3.5 SPM Probes with Actuators 452
12.4 Practical Factors Affecting Yield of MEMS 457
Summary 458
Problems 458
References 462
Chapter 13 Polymer MEMS 465
13.0 Preview 465
13.1 Introduction 465
13.2 Polymers in MEMS 467
13.2.1 Polyimide 469
13.2.2 SU-8 469
13.2.3 Liquid Crystal Polymer (LCP) 470
13.2.4 PDMS 471
13.2.5 PMMA 473
13.2.6 Parylene 473
13.2.7 Fluorocarbon 474
13.2.8 Other Polymers 474
13.3 Representative Applications 475
13.3.1 Acceleration Sensors 475
13.3.2 Pressure Sensors 477
13.3.3 Flow Sensors 481
13.3.4 Tactile Sensors 483
Summary 486
Problems 486
References 487
Chapter 14 Micro Fluidics Applications 491
14.0 Preview 491
14.1 Motivation for Microfluidics 491
14.2 Essential Biology Concepts 492
14.3 Basic Fluid Mechanics Concepts 495
14.3.1 The Reynolds Number and Viscosity 495
14.3.2 Methods for Fluid Movement in Channels 497
14.3.3 Pressure Driven Flow 497
14.3.4 Electrokinetic Flow 500
14.3.5 Electrophoresis and Dielectrophoresis 501
14.4 Design and Fabrication of Selective Components 503
14.4.1 Channels 503
14.4.2 Valves 515
Summary 518
Problems 518
References 520
Chapter 15 Case Studies of Selected MEMS Products 525
15.0 Preview 525
15.1 Case Studies: Blood Pressure (BP) Sensor 526
15.1.1 Background and History 526
15.1.2 Device Design Considerations 527
15.1.3 Commercial Case: NovaSensor BP Sensor 528
15.2 Case Studies: Microphone 530
15.2.1 Background and History 530
15.2.2 Design Considerations 531
15.2.3 Commercial Case: Knowles Microphone 532
15.3 Case Studies: Acceleration Sensors 533
15.3.1 Background and History 533
15.3.2 Design Considerations 533
15.3.3 Commercial Case: Analog Devices and MEMSIC 537
15.4 Case Studies: Gyros 538
15.4.1 Background and History 538
15.4.2 The Coriolis Force 538
15.4.3 MEMS Gyro Design 540
15.4.4 Single Axis Gyro Dynamics 542
15.4.5 Commercial Case: InvenSense Gyro 544
15.5 Summary of Top Concerns for MEMS Product Development 545
15.5.1 Performance and Accuracy 546
15.5.2 Repeatability and Reliability 546
15.5.3 Managing the Cost of MEMS Products 547
15.5.4 Market Uncertainties, Investment, and Competition 547
Summary 548
Problems 548
References 552
Appendix 1 Characteristics of Selected MEMS Materials 553
Appendix 2 Frequently Used Formula for Beams, Cantilevers, and Plates 556
Appendix 3 Basic Tools for Dealing with a Mechanical Second-order Dynamic System 558
Appendix 4 Most Commonly Encountered Materials 562
Appendix 5 Most Commonly Encountered Material Removal Process Steps 563
Appendix 6 A List of General Compatibility between General Materials and Processes 564
Appendix 7 Comparison of Commercial Inertial Sensors 567
Answers to Selected Problems 569
Index 571