MEMS Materials and Processes Handbook - Home - …978-0-387-47318-5/1.pdf · MEMS Materials and Processes Handbook 123. Editors ... microturbine, Analog Devices ... culminated in

MEMS Materials and Processes Handbook

MEMS Reference ShelfSeries Editors:

Stephen D. Senturia Roger T. HoweProfessor of Electrical Professor Department

Engineering, Emeritus of Electrical EngineeringMassachusetts Institute Stanford University

of Technology Stanford, CaliforniaCambridge, Massachusetts

Antonio J. RiccoSmall Satellite DivisionNASA Ames Research CenterMoffett Field, California

For other titles in this series, go to:www.springer.com/series/7724

Reza Ghodssi · Pinyen LinEditors

MEMS Materialsand Processes Handbook

123

EditorsReza GhodssiDepartment of Electrical and Computer

EngineeringInstitute for Systems ResearchMEMS Sensors and Actuators LaboratoryUniversity of MarylandCollege Park, [email protected]

Pinyen LinTouch Micro-system Technology Corp.TaoyuanTaiwanand

Walsin Lihwa [email protected]

ISSN 1936-4407ISBN 978-0-387-47316-1 e-ISBN 978-0-387-47318-5DOI 10.1007/978-0-387-47318-5Springer New York Dordrecht Heidelberg London

Library of Congress Control Number: 2011921730

© Springer Science+Business Media, LLC 2011All rights reserved. This work may not be translated or copied in whole or in part without the writtenpermission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York,NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis. Usein connection with any form of information storage and retrieval, electronic adaptation, computersoft-ware, or by similar or dissimilar methodology now known or hereafter developed is forbidden.The use in this publication of trade names, trademarks, service marks, and similar terms, even if they arenot identified as such, is not to be taken as an expression of opinion as to whether or not they are subjectto proprietary rights.

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Springer is part of Springer Science+Business Media (www.springer.com)

Foreword

The field that is affectionately known as “MEMS” (an acronym for Micro-Electro-Mechanical Systems) is a descendant of the integrated circuits industry, but adescendent that has developed in ways and directions never anticipated by its par-ent. Now a highly specialized discipline in its own right, MEMS draws not only onall of conventional microelectronics but also on novel fabrication methods and usesof non-microelectronic materials to create devices that are mechanical, or fluidic, orbiochemical, or optical, many without any transistors in sight. The key words aresensors and actuators, sometimes combined with (or without) microelectronics tocreate complete microsystems. MEMS devices and microsystems are now foundeverywhere – in automobiles, in ink-jet printers, in computer games, in mobiletelephones, in forensic labs, in factories, in sophisticated instrumentation systemslaunched into space, in the operating room and in the clinic. The genie is out of thebottle. MEMS devices are everywhere.

Because of this immense diversity, no single book can capture the essence ofthe entire field. But all MEMS devices represent highly specific answers to twocritical questions: “How shall I make it? And from what materials shall I make it?”Processes and materials. Materials and processes. Because these two challenges arecommon to all MEMS devices, it makes sense to gather the wisdom of the leastseveral decades on “how to make it” and “from what materials” into a single data-rich, process-detail-rich compendium. That is the raison d’etre for this volume, andthat is its goal: to document MEMS processes and materials at a sufficient level ofdetail to be of significant practical use.

I congratulate the co-Editors, Reza Ghodssi and Pinyen Lin, as well as our con-sulting editors and all of the contributors, for their diligence, persistence, care, andskill in bringing this material to published form, and I invite the MEMS commu-nity world-wide to benefit from the knowledge, wisdom and cumulative expertisegathered into these pages.

Brookline, Massachusetts Stephen D. SenturiaJune 2010

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Preface

Throughout the relatively short history of microelectromechanical systems(MEMS), there have been numerous advances and inventions directly related todevice fabrication. From humble beginnings using borrowed and modified IC fabri-cation techniques to current MEMS-specific tools such as deep reactive ion etching(DRIE) using inductively coupled plasma (ICP) sources, MEMS researchers havecontinually advanced and augmented the capabilities of wafer-based fabricationtechnologies. These advances have been instrumental in the demonstration of newdevices and applications – Texas Instruments’ Digital Micromirror Device, the MITmicroturbine, Analog Devices’ accelerometers – and even in the creation of newfields of research and development: bioMEMS, microfluidic devices, and opticalMEMS.

To date, a number of books have been written about these new fabrication tech-nologies and materials in general, but discussion of their relationship to MEMSdesign has been minimal. As a particularly diverse and multidisciplinary area ofresearch, the field of MEMS offers a vastly different set of challenges relative totypical IC fabrication and design. Much effort is often focused on characterizationruns and developing in-house recipes and specific processes to develop and man-ufacture MEMS structures, each time at the risk of wasting research efforts and“reinventing the wheel.” A wealth of knowledge exists in the MEMS community,but much of this expertise is most readily accessed by informal, nonmethodologicalmeans such as discussions with colleagues at conferences. The authors of this bookhave observed an unnecessarily steep learning curve for the development of com-mon MEMS processes, and believe the time spent traversing this curve would bebetter spent brainstorming new ideas and uncovering new applications. This bookwas conceived and born of this belief.

A fundamental and comprehensive MEMS-focused reference book will be animportant asset for current and future research scientists and engineers. It wasdecided early in the brainstorming sessions for this book to include materials aswell as processes in the discussion, as MEMS utilizes a wide variety of each incommon applications. We intend this book to provide the reader with the basics ofMEMS materials and processes, but beyond this goal, we intend for it to give prac-tical insight into the workings and standard procedures carried out in research labs

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and production facilities on a daily basis. To this end, each chapter has an extendedsection with case studies, giving step-by-step examples and recipes prepared byexperts in industry and academia. Particularly, the effect of processing conditionson material properties are covered where applicable, illustrating the interdepen-dence and multidisciplinary nature of MEMS fabrication. The chapters are meantto be a springboard of sorts, providing basic information about each topic, with alarge number of classic and contemporary literature references to provide in-depthknowledge. Ultimately, it is our goal to provide a useful design reference volume forthe seasoned researcher and the MEMS newcomer alike. We hope this book consol-idates important information for readers and thereby spurs the creation of many newdevices and processes.

MEMS devices are essentially microsystems that have structures and emptyspace built together. The authors of this book view the materials and processesas the fundamental building blocks for making those structures and empty spaces.Keeping this in mind, the book is divided into two main sections: Chapters 2, 3, 4,5, and 6 covering materials and Chapters 7, 8, 9, 10, 11, 12, and 13 covering fab-rication techniques. These two general thrusts are bookended by Chapter 1, whichdiscusses general MEMS design, and Chapter 14, which deals with MEMS processintegration.

Chapter 1 provides a basic framework for the design of MEMS systems and pro-cesses, which we highly recommend reading before diving into the materials andprocess sections of the book. Chapter 2 presents an overview of the recipes andmethods used in the deposition of semiconductor and dielectric thin-films, partic-ularly those most commonly used in the fabrication of MEMS. The basics hereinclude chemical vapor deposition, epitaxy, physical vapor deposition, atomic layerdeposition, and spin-on techniques. Additive processes for depositing metal filmsare discussed in detail in Chapter 3, where particular attention is paid to thickmetal deposition with significant coverage devoted to electrochemical and electro-less plating processes that are often required for MEMS fabrication. The entirety ofChapter 4 is devoted to the use of polymeric materials for MEMS. Polymers, such aspolydimethylsiloxane (PDMS), are important materials for a vast array of devices,as encapsulants for tactile sensors and as an integral enabling technology for theemerging field of bioMEMS. The piezoelectric films detailed in Chapter 5 are animportant part of MEMS technology, serving as both sensor and actuator elements.The basic properties of these materials and the physics of operation are describedin detail as well as practical deposition and fabrication methods. Chapter 6 focuseson the fabrication and integration of shape memory alloy (SMA) materials, whichprovide high-force and high-displacement actuator mechanisms for MEMS.

Chapter 7 begins the section on processing of materials for MEMS applicationsby covering the very important area of dry etching methods (including DRIE),particularly the influence of different parameters on the etch recipe developmentprocess. Complementing the coverage of dry etching, wet etching processes forMEMS micromachining are covered in Chapter 8 with a comprehensive recipe andreference list included in this chapter to aid in finding etch rates and etch selectivitiesfor a wide range of materials from silicon to III–V compound semiconductors.

Preface ix

Chapter 9 describes the technology of lithography and related techniques, cov-ering traditional contact lithography, projection and X-ray lithography, and moreexotic direct-write and printing lithographic techniques. Doping processes typical inand for MEMS applications for electrical purposes and etching control are reviewedin Chapter 10, along with diagnostic techniques for these methods. Wafer bond-ing, a crucial fabrication technique for silicon MEMS encapsulation and structurefabrication, is covered in detail in Chapter 11 with emphasis placed on direct andintermediate layer bonding methods.

Chapter 12 discusses the still-evolving field of MEMS packaging, pointing outdifferences with current microcircuit packaging techniques; this chapter in partic-ular highlights how MEMS devices present very unique challenges as comparedto traditional microcircuits. Surface treatments for MEMS devices are discussed inChapter 13, covering antistiction and planarization coatings, functionalization ofsurfaces for biological and optical applications, and chemical mechanical polishing(CMP). Chapter 14 concludes the book with a discussion of the integration of anynumber of the above processes and materials into a compatible and efficient pro-cess flow, referred to here as process integration. The final chapter also discusseseconomic and practical aspects of process integration, citing some commerciallysuccessful examples of MEMS devices.

This reference volume would not have been possible without the help of many ofour colleagues in the MEMS fields, from both academia and industry. We would liketo extend words of thanks and gratitude to Stephen (Steve) Senturia for providingthe vision, support, and guidance to our team over the past five years in navigatingthe completion of the chapters and for reviewing them diligently, and to the SeriesAssociate Editors Roger Howe and Antonio (Tony) Ricco for carefully reviewingthe chapters, providing helpful comments, and for recommending prospective con-tributing authors. We thank Steven (Steve) Elliot, from Springer, for his patience indealing with thirty-five unique and independent experts, and his persistence in con-tacting each of us in order to develop the logistics for the book publishing process.Last but not least, we acknowledge all thirty-five contributing authors, who self-lessly gave time, expertise, effort, and creativity to make this book a one-of-a-kindcontribution to the current and future MEMS community, including industry andgovernment professionals, academic faculty and staff, and students.

The idea for this book was born at the Transducers 2005 Conference in Seoul,South Korea, and it was finalized and finished at The Hilton Head 2010 Workshopon Hilton Head Island, South Carolina. The five years of cooperative activity thatculminated in this handbook prove that great ideas can become reality when col-leagues work collaboratively to achieve a common goal. This message, which wehave tried to convey by writing this book, is what the greater MEMS community isall about.

College Park, Maryland Reza GhodssiTaoyuan, Taiwan Pinyen Lin

Contents

1 The MEMS Design Process . . . . . . . . . . . . . . . . . . . . . . 11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.1 Design Process . . . . . . . . . . . . . . . . . . . . . 51.2 Design Methods for MEMS . . . . . . . . . . . . . . . . . . . 7

1.2.1 History of Design Methodologies . . . . . . . . . . . 71.2.2 Structured Design Methods for MEMS . . . . . . . . 8

1.3 Brainstorming . . . . . . . . . . . . . . . . . . . . . . . . . . 91.4 Microphone Case Studies . . . . . . . . . . . . . . . . . . . . 10

1.4.1 Microphone Background . . . . . . . . . . . . . . . 101.4.2 The Avago Story . . . . . . . . . . . . . . . . . . . . 11

1.4.2.1 Design Process and Methods . . . . . . . 111.4.3 The Knowles Story . . . . . . . . . . . . . . . . . . 201.4.4 Summary of Key Concepts . . . . . . . . . . . . . . 22

1.5 Materials and Process Selection . . . . . . . . . . . . . . . . . 231.5.1 Materials Selection . . . . . . . . . . . . . . . . . . . 231.5.2 Process Selection . . . . . . . . . . . . . . . . . . . 23

1.6 Evaluate Concepts . . . . . . . . . . . . . . . . . . . . . . . . 301.6.1 Modeling . . . . . . . . . . . . . . . . . . . . . . . . 30

1.7 Optimization and Other Design Methods . . . . . . . . . . . . 311.7.1 Design Optimization . . . . . . . . . . . . . . . . . . 311.7.2 Uncertainty Analysis . . . . . . . . . . . . . . . . . . 311.7.3 FMEA . . . . . . . . . . . . . . . . . . . . . . . . . 311.7.4 Design Method Timing . . . . . . . . . . . . . . . . 32

1.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

2 Additive Processes for Semiconductors and DielectricMaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372.2 Thermal Conversion . . . . . . . . . . . . . . . . . . . . . . . 38

2.2.1 Process Overview . . . . . . . . . . . . . . . . . . . 38

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2.2.2 Material Properties and Process SelectionGuide for Thermal Oxidation of Silicon . . . . . . . . 43

2.2.3 Case Studies . . . . . . . . . . . . . . . . . . . . . . 452.3 Chemical Vapor Deposition . . . . . . . . . . . . . . . . . . . 45

2.3.1 Process Overviews . . . . . . . . . . . . . . . . . . . 452.3.1.1 Introduction . . . . . . . . . . . . . . . . 452.3.1.2 Low Pressure Chemical Vapor

Deposition . . . . . . . . . . . . . . . . . 472.3.1.3 Plasma-Enhanced Chemical

Vapor Deposition . . . . . . . . . . . . . 502.3.1.4 Atmospheric Pressure Chemical

Vapor Deposition . . . . . . . . . . . . . 522.3.1.5 Hot Filament Chemical Vapor

Deposition . . . . . . . . . . . . . . . . . 532.3.1.6 Microwave Plasma Chemical

Vapor Deposition . . . . . . . . . . . . . 532.3.2 LPCVD Polycrystalline Silicon . . . . . . . . . . . . 53

2.3.2.1 Material Properties and ProcessGeneralities . . . . . . . . . . . . . . . . 53

2.3.2.2 Process Selection Guidelines . . . . . . . 552.3.2.3 Case Studies . . . . . . . . . . . . . . . . 56

2.3.3 LPCVD Silicon Dioxide . . . . . . . . . . . . . . . . 652.3.3.1 Material Properties and Process

Generalities . . . . . . . . . . . . . . . . 652.3.3.2 Process Selection Guidelines . . . . . . . 662.3.3.3 Case Studies . . . . . . . . . . . . . . . . 67

2.3.4 LPCVD Silicon Nitride . . . . . . . . . . . . . . . . 692.3.4.1 Material Properties and Process


2.3.5 LPCVD Polycrystalline SiGe and Ge . . . . . . . . . 732.3.5.1 Material Properties and Process

Generalities . . . . . . . . . . . . . . . . 732.3.5.2 Process Selection Guidelines . . . . . . . 75

2.3.6 LPCVD Polycrystalline Silicon Carbide . . . . . . . 752.3.6.1 Material Properties and Process


2.3.7 LPCVD Diamond . . . . . . . . . . . . . . . . . . . 852.3.7.1 Material Properties and Process


Contents xiii

2.3.8 APCVD Polycrystalline Silicon Carbide . . . . . . . 892.3.8.1 Material Properties and Process


2.3.9 PECVD Silicon . . . . . . . . . . . . . . . . . . . . 892.3.9.1 Material Properties and Process


2.3.10 PECVD Silicon Dioxide . . . . . . . . . . . . . . . . 912.3.10.1 Material Properties and Process


2.3.11 PECVD Silicon Nitride . . . . . . . . . . . . . . . . 952.3.11.1 Material Properties and Process


2.3.12 PECVD Silicon Germanium . . . . . . . . . . . . . . 952.3.12.1 Material Properties and Process


2.3.13 PECVD Silicon Carbide . . . . . . . . . . . . . . . . 1012.3.13.1 Material Properties and Process


2.3.14 PECVD Carbon-Based Films . . . . . . . . . . . . . 1042.3.14.1 Material Properties and Process


2.4 Epitaxy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1052.4.1 Process Overviews . . . . . . . . . . . . . . . . . . . 1052.4.2 Epi-Polysilicon . . . . . . . . . . . . . . . . . . . . . 106



2.4.3 Epitaxial Silicon Carbide . . . . . . . . . . . . . . . 1082.4.3.1 Material Properties and Process


2.4.4 III-V Materials and Gallium Nitride . . . . . . . . . . 1112.4.4.1 Material Properties and Process

Generalities . . . . . . . . . . . . . . . . 111

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2.5 Physical Vapor Deposition . . . . . . . . . . . . . . . . . . . 1142.5.1 Process Overviews . . . . . . . . . . . . . . . . . . . 1142.5.2 Sputter-Deposited Si . . . . . . . . . . . . . . . . . . 115


2.5.2.2 Process Selection Guidelines . . . . . . . 1162.5.3 Sputter-Deposited SiC . . . . . . . . . . . . . . . . . 1162.5.4 Sputter-Deposited SiO2 . . . . . . . . . . . . . . . . 1172.5.5 Sputter-Deposited Diamondlike Carbon . . . . . . . . 1182.5.6 Carbon Films Deposited by Pulsed Laser Deposition . 118

2.6 Atomic Layer Deposition . . . . . . . . . . . . . . . . . . . . 1192.6.1 Process Overview . . . . . . . . . . . . . . . . . . . 1192.6.2 Process Selection Guidelines and Material Properties . 120

2.7 Spin-On Films . . . . . . . . . . . . . . . . . . . . . . . . . . 121References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

3 Additive Processes for Metals . . . . . . . . . . . . . . . . . . . . 1373.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

3.1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . 1383.1.2 Fabrication Tradeoffs . . . . . . . . . . . . . . . . . 139

3.2 Physical Vapor Deposition . . . . . . . . . . . . . . . . . . . 1403.2.1 Evaporation . . . . . . . . . . . . . . . . . . . . . . 140

3.2.1.1 Thermal Evaporation . . . . . . . . . . . 1413.2.1.2 E-Beam Evaporation . . . . . . . . . . . 1423.2.1.3 Issues with Alloys . . . . . . . . . . . . . 142

3.2.2 Sputtering . . . . . . . . . . . . . . . . . . . . . . . 1423.2.2.1 DC Sputtering . . . . . . . . . . . . . . . 1433.2.2.2 RF Sputtering . . . . . . . . . . . . . . . 1443.2.2.3 Step Coverage . . . . . . . . . . . . . . . 1443.2.2.4 Other Issues in Sputtering . . . . . . . . . 145

3.2.3 Pulsed Laser Deposition . . . . . . . . . . . . . . . . 1463.3 Electrochemical Deposition . . . . . . . . . . . . . . . . . . . 147

3.3.1 Electroplating . . . . . . . . . . . . . . . . . . . . . 1473.3.1.1 Electrochemical Reactions . . . . . . . . 1473.3.1.2 Deposition Process . . . . . . . . . . . . 1493.3.1.3 Overpotential . . . . . . . . . . . . . . . 1523.3.1.4 Bath Composition . . . . . . . . . . . . . 1533.3.1.5 Current Waveform . . . . . . . . . . . . . 1533.3.1.6 Equipment . . . . . . . . . . . . . . . . . 1553.3.1.7 Process Flow . . . . . . . . . . . . . . . 1573.3.1.8 Nickel . . . . . . . . . . . . . . . . . . . 1583.3.1.9 Copper . . . . . . . . . . . . . . . . . . . 1593.3.1.10 Gold . . . . . . . . . . . . . . . . . . . . 159

Contents xv

3.3.1.11 Nickel Alloys . . . . . . . . . . . . . . . 1613.3.2 Electroless Plating . . . . . . . . . . . . . . . . . . . 162

3.3.2.1 Nickel . . . . . . . . . . . . . . . . . . . 1643.3.2.2 Copper . . . . . . . . . . . . . . . . . . . 1663.3.2.3 Gold . . . . . . . . . . . . . . . . . . . . 168

3.3.3 Comparison of Electroplating and ElectrolessPlating . . . . . . . . . . . . . . . . . . . . . . . . . 169

3.4 LIGA and UV-LIGA Processes . . . . . . . . . . . . . . . . . 1693.4.1 Process Explanation . . . . . . . . . . . . . . . . . . 1703.4.2 Electroplating in LIGA and UV-LIGA

Microstructures . . . . . . . . . . . . . . . . . . . . 1713.4.3 Multilevel Metal Structures . . . . . . . . . . . . . . 173

3.5 Materials Properties and Process Selection Guidelinesfor Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1793.5.1 Adhesion . . . . . . . . . . . . . . . . . . . . . . . . 1793.5.2 Electrical Properties . . . . . . . . . . . . . . . . . . 1803.5.3 Mechanical Properties . . . . . . . . . . . . . . . . . 1823.5.4 Thermal Properties . . . . . . . . . . . . . . . . . . . 1833.5.5 Magnetic Properties . . . . . . . . . . . . . . . . . . 184

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

4 Additive Processes for Polymeric Materials . . . . . . . . . . . . . 1934.1 SU-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

4.1.1 Material Properties . . . . . . . . . . . . . . . . . . . 1954.1.2 Processing Variations . . . . . . . . . . . . . . . . . 196

4.1.2.1 Partial Exposure . . . . . . . . . . . . . . 1964.1.2.2 Direct Writing . . . . . . . . . . . . . . . 1974.1.2.3 Removal of SU-8 . . . . . . . . . . . . . 1974.1.2.4 Release of SU-8 . . . . . . . . . . . . . . 1984.1.2.5 Bonding . . . . . . . . . . . . . . . . . . 1984.1.2.6 Transfer . . . . . . . . . . . . . . . . . . 1994.1.2.7 SU-8 as an Etch Mask . . . . . . . . . . . 199

4.1.3 Lessons Learned . . . . . . . . . . . . . . . . . . . . 1994.1.4 Examples of SU-8 Application . . . . . . . . . . . . 201

4.2 PDMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2014.2.1 Material Properties . . . . . . . . . . . . . . . . . . . 2024.2.2 Processing Techniques . . . . . . . . . . . . . . . . . 2034.2.3 Biological Application Guide . . . . . . . . . . . . . 205

4.2.3.1 Stamp Material for ProteinTransfer: Microcontact Printing . . . . . . 206

4.2.3.2 Microfluidic Devices . . . . . . . . . . . 2064.2.4 Case Study . . . . . . . . . . . . . . . . . . . . . . . 208

4.3 Polyimide . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2124.3.1 Material Properties . . . . . . . . . . . . . . . . . . . 2124.3.2 Processing Variations . . . . . . . . . . . . . . . . . 213

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4.3.2.1 Removal of Polyimide . . . . . . . . . . 2134.3.2.2 Release of Polyimide . . . . . . . . . . . 2134.3.2.3 Bonding . . . . . . . . . . . . . . . . . . 215

4.3.3 Lessons Learned . . . . . . . . . . . . . . . . . . . . 2154.3.4 Case Study . . . . . . . . . . . . . . . . . . . . . . . 216

4.4 Hydrogels . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2164.4.1 Gelatin . . . . . . . . . . . . . . . . . . . . . . . . . 2164.4.2 Chitosan . . . . . . . . . . . . . . . . . . . . . . . . 2184.4.3 Polyethylene Glycol . . . . . . . . . . . . . . . . . . 2204.4.4 Case Studies . . . . . . . . . . . . . . . . . . . . . . 222

4.5 Parylene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2234.5.1 Material Properties . . . . . . . . . . . . . . . . . . . 2244.5.2 Processing Techniques . . . . . . . . . . . . . . . . . 2254.5.3 Lessons Learned . . . . . . . . . . . . . . . . . . . . 2264.5.4 Case Study . . . . . . . . . . . . . . . . . . . . . . . 226

4.6 Conductive Polymers . . . . . . . . . . . . . . . . . . . . . . 2274.6.1 Material Properties . . . . . . . . . . . . . . . . . . . 2284.6.2 Actuation Mechanism and Theories . . . . . . . . . . 2294.6.3 Applications . . . . . . . . . . . . . . . . . . . . . . 230

4.6.3.1 Actuators . . . . . . . . . . . . . . . . . 2304.6.3.2 Conducting Polymer as a Strain

Gauge Material . . . . . . . . . . . . . . 2314.6.4 Processing Techniques . . . . . . . . . . . . . . . . . 231

4.6.4.1 Deposition . . . . . . . . . . . . . . . . . 2314.6.4.2 Patterning . . . . . . . . . . . . . . . . . 2324.6.4.3 Release . . . . . . . . . . . . . . . . . . 2324.6.4.4 Process Considerations . . . . . . . . . . 233

4.6.5 Case Study . . . . . . . . . . . . . . . . . . . . . . . 2334.7 Other Polymers . . . . . . . . . . . . . . . . . . . . . . . . . 235

4.7.1 Benzocyclobutene . . . . . . . . . . . . . . . . . . . 2354.7.2 Liquid Crystal Polymer . . . . . . . . . . . . . . . . 238

4.8 Polymers for Embossing and Molding . . . . . . . . . . . . . 2394.8.1 Technical Overview . . . . . . . . . . . . . . . . . . 2394.8.2 Substrate Material Selection . . . . . . . . . . . . . . 241

4.8.2.1 Polymethylmethacrylate . . . . . . . . . 2414.8.2.2 Polycarbonate . . . . . . . . . . . . . . . 2424.8.2.3 Polytetrafluoroethylene . . . . . . . . . . 2424.8.2.4 Cyclic Olefin Copolymer . . . . . . . . . 242

4.8.3 Tool Selection . . . . . . . . . . . . . . . . . . . . . 2424.8.4 Mold Material Selection and Fabrication . . . . . . . 243

4.8.4.1 Silicon . . . . . . . . . . . . . . . . . . . 2434.8.4.2 Nickel . . . . . . . . . . . . . . . . . . . 2444.8.4.3 SU-8 . . . . . . . . . . . . . . . . . . . . 245

4.8.5 Conventional Machining of Molds . . . . . . . . . . 2464.8.5.1 Milling . . . . . . . . . . . . . . . . . . 246

Contents xvii

4.8.5.2 Laser . . . . . . . . . . . . . . . . . . . . 2474.8.5.3 Focused Ion Beam . . . . . . . . . . . . . 2474.8.5.4 Fixture of Molds . . . . . . . . . . . . . 2474.8.5.5 Release Coatings . . . . . . . . . . . . . 247

4.8.6 Process Development . . . . . . . . . . . . . . . . . 2474.8.7 Minimum Substrate Thickness . . . . . . . . . . . . 249

4.9 Materials Properties . . . . . . . . . . . . . . . . . . . . . . . 250References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250

5 Additive Processes for Piezoelectric Materials:Piezoelectric MEMS . . . . . . . . . . . . . . . . . . . . . . . . . . 2735.1 Introduction to Piezoelectric Thin Films . . . . . . . . . . . . 273

5.1.1 Direct and Converse Piezoelectricity . . . . . . . . . 2755.1.2 Materials – Ferroelectrics and Nonferroelectrics . . . 2765.1.3 Fundamental Design Equations and Models . . . . . . 281

5.1.3.1 Linear Constitutive Equations ofPiezoelectricity . . . . . . . . . . . . . . 281

5.1.3.2 Electromechanical Coupling Factors . . . 2825.1.3.3 Influence of Boundary Conditions . . . . 2845.1.3.4 Device Configurations . . . . . . . . . . 2855.1.3.5 Free Strain and Blocking Force . . . . . . 2875.1.3.6 Cantilever Unimorph Model . . . . . . . 2885.1.3.7 Actuator Force Generation

Against External Loads . . . . . . . . . . 2915.1.3.8 Piezoelectric Sensing . . . . . . . . . . . 2925.1.3.9 Equivalent Circuit Models . . . . . . . . 2945.1.3.10 Thin-Film Ferroelectric Nonlinearity . . . 2955.1.3.11 Heat Generation . . . . . . . . . . . . . . 299

5.1.4 Materials Selection Guide . . . . . . . . . . . . . . . 2995.1.5 Applications . . . . . . . . . . . . . . . . . . . . . . 300

5.2 Polar Materials: AlN and ZnO . . . . . . . . . . . . . . . . . 3015.2.1 Material Deposition . . . . . . . . . . . . . . . . . . 3015.2.2 Patterning Techniques . . . . . . . . . . . . . . . . . 3055.2.3 Device-Design Concerns . . . . . . . . . . . . . . . . 3075.2.4 Device Examples . . . . . . . . . . . . . . . . . . . 3095.2.5 Case Study . . . . . . . . . . . . . . . . . . . . . . . 313

5.3 Ferroelectrics: PZT . . . . . . . . . . . . . . . . . . . . . . . 3185.3.1 Material Deposition . . . . . . . . . . . . . . . . . . 3185.3.2 Patterning Techniques . . . . . . . . . . . . . . . . . 3245.3.3 Device Design Concerns . . . . . . . . . . . . . . . . 3285.3.4 Device Examples . . . . . . . . . . . . . . . . . . . 3335.3.5 Case Study on the Design and Processing of a

RF MEMS Switch Using PZT Thin-Film Actuators . 3385.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344

xviii Contents

6 Materials and Processes in Shape Memory Alloy . . . . . . . . . . 3556.1 Introduction and Principle . . . . . . . . . . . . . . . . . . . . 355

6.1.1 Basic Principle . . . . . . . . . . . . . . . . . . . . . 3556.1.2 Introduction of TiNi and TiNi-Base Ternary Alloys . . 3576.1.3 Super-Elasticity . . . . . . . . . . . . . . . . . . . . 3596.1.4 One-Way Type, Two-Way Type,

All-Round-Way Type . . . . . . . . . . . . . . . . . 3596.2 Materials Properties and Fabrication Process

of SMA Actuators . . . . . . . . . . . . . . . . . . . . . . . . 3606.2.1 Bulk Material . . . . . . . . . . . . . . . . . . . . . 3616.2.2 Thin Film . . . . . . . . . . . . . . . . . . . . . . . 361

6.2.2.1 Sputtering . . . . . . . . . . . . . . . . . 3626.2.2.2 Evaporation . . . . . . . . . . . . . . . . 3636.2.2.3 Non-planar Thin Film Deposition . . . . . 363

6.2.3 Micromachining . . . . . . . . . . . . . . . . . . . . 3646.2.4 Etching and Lift-Off . . . . . . . . . . . . . . . . . . 365

6.2.4.1 Case and Example . . . . . . . . . . . . . 3656.2.5 Assembly . . . . . . . . . . . . . . . . . . . . . . . . 369

6.2.5.1 Mechanical Fixation . . . . . . . . . . . . 3696.2.5.2 Adhesion . . . . . . . . . . . . . . . . . 3696.2.5.3 Welding . . . . . . . . . . . . . . . . . . 3696.2.5.4 Soldering . . . . . . . . . . . . . . . . . 371

6.2.6 Materials and Processes Selection Guidance . . . . . 3716.2.6.1 Materials (Bulk/Thin Film) . . . . . . . . 3716.2.6.2 Process . . . . . . . . . . . . . . . . . . 375

6.3 Applications and Devices . . . . . . . . . . . . . . . . . . . . 3786.3.1 Medical . . . . . . . . . . . . . . . . . . . . . . . . 378

6.3.1.1 Stents . . . . . . . . . . . . . . . . . . . 3786.3.1.2 Endoscopes . . . . . . . . . . . . . . . . 3786.3.1.3 Catheters . . . . . . . . . . . . . . . . . 3796.3.1.4 Micro Clips and Grippers . . . . . . . . . 384

6.3.2 Fluidic Devices . . . . . . . . . . . . . . . . . . . . 3876.3.3 Optical Fiber Switch . . . . . . . . . . . . . . . . . . 3906.3.4 Tactile Pin Display . . . . . . . . . . . . . . . . . . . 3906.3.5 AFM Cantilever . . . . . . . . . . . . . . . . . . . . 3926.3.6 Case Studies and Lessons Learned . . . . . . . . . . 393

6.3.6.1 Designs . . . . . . . . . . . . . . . . . . 3936.3.6.2 Heating and Cooling . . . . . . . . . . . 394


7 Dry Etching for Micromachining Applications . . . . . . . . . . . 4037.1 Dry Etching . . . . . . . . . . . . . . . . . . . . . . . . . . . 404

7.1.1 Etch Metrics . . . . . . . . . . . . . . . . . . . . . . 4047.2 Plasma Etching . . . . . . . . . . . . . . . . . . . . . . . . . 407

Contents xix

7.2.1 Types of Etching . . . . . . . . . . . . . . . . . . . . 4087.2.2 Plasma Sources . . . . . . . . . . . . . . . . . . . . 412

7.3 Plasma Process Parameters and Control . . . . . . . . . . . . 4187.3.1 Energy-Driven Anisotropy . . . . . . . . . . . . . . . 4197.3.2 Inhibitor-Driven Anisotropy . . . . . . . . . . . . . . 4207.3.3 Selectivity in Plasma Etching . . . . . . . . . . . . . 421

7.4 Case Study: Etching Silicon, Silicon Dioxide,and Silicon Nitride . . . . . . . . . . . . . . . . . . . . . . . 422

7.5 Case Study: High-Aspect-Ratio Silicon Etch Process . . . . . 4277.5.1 Cryogenic Dry Etching . . . . . . . . . . . . . . . . 4287.5.2 Bosch Process . . . . . . . . . . . . . . . . . . . . . 4297.5.3 Understanding Trends for DRIE Recipe

Development . . . . . . . . . . . . . . . . . . . . . . 4327.6 High-Aspect-Ratio Etching of Piezoelectric Materials . . . . . 434

7.6.1 Case Study: High-Aspect-Ratio Etching ofGlass (Pyrex R©) and Quartz . . . . . . . . . . . . . . 434

7.6.2 High-Aspect-Ratio Etching of PiezoelectricMaterials . . . . . . . . . . . . . . . . . . . . . . . . 438

7.7 Etching of Compound Semiconductors . . . . . . . . . . . . . 4417.7.1 Case Study: Etching of GaAs and AlGaAs . . . . . . 4417.7.2 Case Study: Etching of InP, InGaAs, InSb,

and InAs . . . . . . . . . . . . . . . . . . . . . . . . 4447.8 Case Study: Ion Beam Etching . . . . . . . . . . . . . . . . . 4467.9 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 452

8 MEMS Wet-Etch Processes and Procedures . . . . . . . . . . . . 4578.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 4588.2 Principles and Process Architectures for Wet Etching . . . . . 460

8.2.1 Surface Reactions and Reactant/Product Transport . . 4648.2.2 Etchant Selectivity and Masking Considerations . . . 4678.2.3 Direct Etching and Liftoff Techniques . . . . . . . . . 4698.2.4 Sacrificial Layer Removal . . . . . . . . . . . . . . . 4708.2.5 Substrate Thinning and Removal . . . . . . . . . . . 4718.2.6 Impact on Process Architecture . . . . . . . . . . . . 4728.2.7 Process Development for Wet Etches . . . . . . . . . 4738.2.8 Additional Considerations and Alternatives . . . . . . 476

8.3 Evaluation and Development of Wet-Etch Facilitiesand Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 4798.3.1 Facility Requirements . . . . . . . . . . . . . . . . . 479

8.3.1.1 General Facilities . . . . . . . . . . . . . 4798.3.1.2 Wet-Bench Services . . . . . . . . . . . . 4808.3.1.3 Wet-Bench Equipment . . . . . . . . . . 4808.3.1.4 Safety . . . . . . . . . . . . . . . . . . . 481

8.3.2 Wafer Handling Considerations . . . . . . . . . . . . 482

xx Contents

8.3.3 Safety Concerns . . . . . . . . . . . . . . . . . . . . 4838.3.4 Training . . . . . . . . . . . . . . . . . . . . . . . . 483

8.4 IC-Compatible Materials and Wet Etching . . . . . . . . . . . 4848.4.1 Oxide and Dielectric Etching . . . . . . . . . . . . . 4848.4.2 Silicon, Polysilicon, and Germanium Isotropic

Etching . . . . . . . . . . . . . . . . . . . . . . . . . 4928.4.3 Standard Metal Etching . . . . . . . . . . . . . . . . 4958.4.4 Photoresist Removal Techniques and Wafer

Cleaning Processes . . . . . . . . . . . . . . . . . . . 5018.4.5 Examples: Wet Chemical Etching of

IC-Compatible Materials . . . . . . . . . . . . . . . 5138.4.5.1 Example 1: Wet Etch of

Low-Temperature Oxide . . . . . . . . . 5148.4.5.2 Example 2: Wet Etch of Silicon

Nitride on Silicon . . . . . . . . . . . . . 5158.4.5.3 Example 3: Sacrificial Etch of

Deposited Polysilicon Undera Structural Layer ofStress-Controlled Silicon Nitride . . . . . 515

8.4.5.4 Example 4: Aluminum Etchingover Patterned Nitride, Oxide,and Silicon . . . . . . . . . . . . . . . . 515

8.4.5.5 Example 5: Junction DepthDetermination for an IntegratedMEMS Device . . . . . . . . . . . . . . 515

8.5 Nonstandard Materials and Wet Etching . . . . . . . . . . . . 5168.5.1 Nonstandard Dielectric, Semiconductor, and

Metal Etching . . . . . . . . . . . . . . . . . . . . . 5178.5.2 Plastic and Polymer Etching . . . . . . . . . . . . . . 5178.5.3 Examples: Wet Chemical Etching of

Nonstandard Materials . . . . . . . . . . . . . . . . . 5708.5.3.1 Example 1: BCB Patterning and Etching . 5708.5.3.2 Example 2: COC Patterning and

Solvent Bonding . . . . . . . . . . . . . . 5798.5.3.3 Example 3: LIGA Mold Removal . . . . . 579

8.6 Anisotropic Silicon Etching and Silicon Etch Stops . . . . . . 5798.6.1 Anisotropic Etching of Silicon . . . . . . . . . . . . . 5818.6.2 Heavily Doped Silicon Etch Stops . . . . . . . . . . . 5828.6.3 Lightly Doped Silicon and Silicon–Germanium

Etch Stops . . . . . . . . . . . . . . . . . . . . . . . 5898.6.4 Ion-Implanted Silicon Etch Stops . . . . . . . . . . . 5898.6.5 Electrochemical Etching and Electrochemical

Etch Stops . . . . . . . . . . . . . . . . . . . . . . . 5958.6.6 Photoassisted Silicon Etching and Etch Stops . . . . . 5978.6.7 Thin-Film Etch Stops . . . . . . . . . . . . . . . . . 601

Contents xxi

8.6.8 Examples: Wet Chemical and ElectrochemicalEtch Stops . . . . . . . . . . . . . . . . . . . . . . . 6038.6.8.1 Example 1: Anisotropic Silicon

Etching of an SOI Wafer . . . . . . . . . 6038.6.8.2 Example 2: Heavy Boron-Doped

Etch Stop . . . . . . . . . . . . . . . . . 6048.6.8.3 Example 3: Electrochemical Etch Stop . . 604

8.7 Sacrificial Layer Etching . . . . . . . . . . . . . . . . . . . . 6088.7.1 Sacrificial Layer Removal Techniques . . . . . . . . . 6108.7.2 Sacrificial Oxide Removal for Polysilicon

Microstructures . . . . . . . . . . . . . . . . . . . . 6118.7.3 Alternative Sacrificial and Structural Layer

Combinations . . . . . . . . . . . . . . . . . . . . . 6118.7.4 Etch Accelerator Layers for Enhanced

Sacrificial Layer Removal . . . . . . . . . . . . . . . 6178.7.5 Rinse Liquid Removal and Antistiction Coatings . . . 6198.7.6 Examples: Sacrificial Layer Removal and

Structural Layer Release . . . . . . . . . . . . . . . . 6208.7.6.1 Example 1: Fine-Grain Stress-

Controlled Polysilicon with anOxide Sacrificial Layer . . . . . . . . . . 620

8.7.6.2 Example 2: Poly-SiGe on aPatterned Oxide/Nitride Laminate . . . . 620

8.7.6.3 Example 3: Silicon Nitride on aPolysilicon Sacrificial Layer . . . . . . . 623

8.7.6.4 Example 4: Aluminum on Photoresist . . 6238.8 Porous Silicon Formation with Wet Chemistry . . . . . . . . . 623

8.8.1 Nanoporous, Mesoporous, and MacroporousSilicon Formation . . . . . . . . . . . . . . . . . . . 624

8.8.2 Selective Porous Silicon Removal . . . . . . . . . . . 6258.8.3 Examples: Porous Silicon Formation . . . . . . . . . 625

8.8.3.1 Example 1: Chemical PorousSilicon Formation . . . . . . . . . . . . . 625

8.8.3.2 Example 2: Nanoporous SiliconFormation . . . . . . . . . . . . . . . . . 628

8.8.3.3 Example 3: Mesoporous SiliconFormation . . . . . . . . . . . . . . . . . 628

8.8.3.4 Example 4: Macroporous SiliconFormation . . . . . . . . . . . . . . . . . 629

8.9 Layer Delineation and Defect Determinationwith Wet Etchants . . . . . . . . . . . . . . . . . . . . . . . . 6298.9.1 Dopant Level and Defect Determination with

Wet Etchants . . . . . . . . . . . . . . . . . . . . . . 6308.9.2 Layer Delineation with Wet Etchants . . . . . . . . . 636

xxii Contents

8.9.3 Examples: Layer Delineation and DefectDetermination . . . . . . . . . . . . . . . . . . . . . 6378.9.3.1 Example 1: Metallurgical Junction

Determination . . . . . . . . . . . . . . . 6378.9.3.2 Example 2: Cross-Sectioning and

Layer Delineation . . . . . . . . . . . . . 637References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 638

9 MEMS Lithography and Micromachining Techniques . . . . . . . 6679.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6679.2 UV Lithography . . . . . . . . . . . . . . . . . . . . . . . . . 672

9.2.1 Photo Masks . . . . . . . . . . . . . . . . . . . . . . 6729.2.2 Optical Projection Systems . . . . . . . . . . . . . . 677

9.2.2.1 Contact Aligner . . . . . . . . . . . . . . 6779.2.2.2 Stepper . . . . . . . . . . . . . . . . . . 681

9.2.3 Photoresist . . . . . . . . . . . . . . . . . . . . . . . 6829.2.3.1 Positive Photoresist . . . . . . . . . . . . 6849.2.3.2 Negative Photoresist . . . . . . . . . . . . 6869.2.3.3 Image Reversal for Positive

Resist (Converting Positive Resistinto a Negative Resist) . . . . . . . . . . 687

9.2.4 Substrate . . . . . . . . . . . . . . . . . . . . . . . . 6889.2.5 Processing Steps for UV Lithography . . . . . . . . . 688

9.2.5.1 Deposit Photoresist . . . . . . . . . . . . 6889.2.5.2 Expose Photoresist . . . . . . . . . . . . 6909.2.5.3 Develop Photoresist . . . . . . . . . . . . 6919.2.5.4 Transfer Pattern . . . . . . . . . . . . . . 6919.2.5.5 Remove Photoresist . . . . . . . . . . . . 692

9.3 Grayscale Lithography . . . . . . . . . . . . . . . . . . . . . 6939.3.1 Photomask Pixelation . . . . . . . . . . . . . . . . . 6969.3.2 Photoresist Properties for Grayscale Lithography . . . 697

9.3.2.1 Contrast and Thickness . . . . . . . . . . 6979.3.2.2 Exposure and Developing Times . . . . . 6979.3.2.3 Etch Selectivity . . . . . . . . . . . . . . 698

9.4 X-Ray Lithography . . . . . . . . . . . . . . . . . . . . . . . 6989.4.1 X-Ray Masks . . . . . . . . . . . . . . . . . . . . . 7009.4.2 X-Ray Photoresists . . . . . . . . . . . . . . . . . . . 7029.4.3 Exposure . . . . . . . . . . . . . . . . . . . . . . . . 7029.4.4 Development . . . . . . . . . . . . . . . . . . . . . . 703

9.5 Direct-Write Lithography . . . . . . . . . . . . . . . . . . . . 7049.5.1 E-Beam Lithography . . . . . . . . . . . . . . . . . . 7049.5.2 Ion Beam Lithography and Focused Ion Beam (FIB) . 7089.5.3 Gas-Assisted Electron and Ion Beam Lithography . . 7109.5.4 Dip-Pen Lithography (DPN) . . . . . . . . . . . . . . 711

Contents xxiii

9.5.5 Direct-Write Laser . . . . . . . . . . . . . . . . . . . 7129.5.6 Stereolithography and Microstereolithography . . . . 714

9.6 Print/Imprint Lithography . . . . . . . . . . . . . . . . . . . . 7169.6.1 Inkjet Printing . . . . . . . . . . . . . . . . . . . . . 7199.6.2 Soft Lithography . . . . . . . . . . . . . . . . . . . . 7209.6.3 Nanoimprint Lithography (NIL) . . . . . . . . . . . . 7209.6.4 Transfer Printing . . . . . . . . . . . . . . . . . . . . 722

9.7 Case Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . 7259.7.1 Case Study 1: Substrate Cleaning-RCA Clean(s) . . . 725

9.7.1.1 Recipe Steps . . . . . . . . . . . . . . . . 7269.7.1.2 Notes . . . . . . . . . . . . . . . . . . . 727

9.7.2 Case Study 2: Substrate Cleaning, O2 Plasma Clean . 7279.7.2.1 Recipe Steps . . . . . . . . . . . . . . . . 7279.7.2.2 Note . . . . . . . . . . . . . . . . . . . . 727

9.7.3 Case Study 3: Substrate Cleaning, Solvent Clean . . . 7289.7.3.1 Recipe Steps . . . . . . . . . . . . . . . . 7289.7.3.2 Note . . . . . . . . . . . . . . . . . . . . 728

9.7.4 Case Study 4: Positive Photoresist Processing:General Processing for Shipley 1800 SeriesPhotoresist . . . . . . . . . . . . . . . . . . . . . . . 7289.7.4.1 Recipe Steps . . . . . . . . . . . . . . . . 728

9.7.5 Case Study 5: Positive Photoresist Processing:Specific Processing for Shipley S1813 . . . . . . . . 7299.7.5.1 Recipe Steps . . . . . . . . . . . . . . . . 729

9.7.6 Case Study 6: Positive Photoresist Processing:Specific Processing for OiR 906-10 . . . . . . . . . . 7309.7.6.1 Recipe Steps . . . . . . . . . . . . . . . . 7309.7.6.2 Notes . . . . . . . . . . . . . . . . . . . 731

9.7.7 Case Study 7: Negative PhotoresistProcessing: Specific Processing for NR7-1500PY . . 7319.7.7.1 Recipe Steps . . . . . . . . . . . . . . . . 7319.7.7.2 Note 1 . . . . . . . . . . . . . . . . . . . 7329.7.7.3 Note 2 . . . . . . . . . . . . . . . . . . . 733

9.7.8 Case Study 8: E-Beam Lithography . . . . . . . . . . 7339.7.8.1 Notes on Using the NPGS Software . . . 735

9.7.9 Case Study 9: Fabrication of PDMS Templates . . . . 7359.7.10 Case Study 10: Photomask Fabrication [226, 227] . . 736

9.7.10.1 Photomask Defects . . . . . . . . . . . . 7389.7.10.2 Grayscale Lithography Pixelated

Photomasks . . . . . . . . . . . . . . . . 7399.7.10.3 Mask Manufacturers . . . . . . . . . . . 740

9.7.11 Case Study 11: Multiphoton AbsorptionPolymerization (MAP) . . . . . . . . . . . . . . . . . 740

xxiv Contents

9.7.12 Case Study 12: Lithography Using FocusedIon Beams . . . . . . . . . . . . . . . . . . . . . . . 741

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 743

10 Doping Processes for MEMS . . . . . . . . . . . . . . . . . . . . . 75510.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75510.2 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . 756

10.2.1 Electrical Properties . . . . . . . . . . . . . . . . . . 75610.2.2 Etch Stop Techniques . . . . . . . . . . . . . . . . . 76510.2.3 Materials and Process Selection Guidelines:

Etch Stop Techniques . . . . . . . . . . . . . . . . . 77110.3 In Situ Doping . . . . . . . . . . . . . . . . . . . . . . . . . . 774

10.3.1 Chemical Vapor Deposition . . . . . . . . . . . . . . 77410.3.2 Crystal Growth and Epitaxy . . . . . . . . . . . . . . 777

10.4 Diffusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78110.4.1 Gas Phase Diffusion . . . . . . . . . . . . . . . . . . 78310.4.2 Solid State Diffusion . . . . . . . . . . . . . . . . . . 78410.4.3 Masking Materials . . . . . . . . . . . . . . . . . . . 78610.4.4 Modeling . . . . . . . . . . . . . . . . . . . . . . . . 787

10.5 Ion Implantation . . . . . . . . . . . . . . . . . . . . . . . . . 78810.5.1 Equipment . . . . . . . . . . . . . . . . . . . . . . . 79010.5.2 Masking Materials . . . . . . . . . . . . . . . . . . . 79210.5.3 Modeling . . . . . . . . . . . . . . . . . . . . . . . . 79310.5.4 Crystal Damage . . . . . . . . . . . . . . . . . . . . 79310.5.5 Buried Insulator Layers . . . . . . . . . . . . . . . . 79510.5.6 Case Study: Heavily Doped Polysilicon . . . . . . . . 795

10.6 Plasma Doping Processes . . . . . . . . . . . . . . . . . . . . 79810.7 Dopant Activation Methods . . . . . . . . . . . . . . . . . . . 800

10.7.1 Conventional Annealing Methods . . . . . . . . . . . 80010.7.2 Rapid Thermal Processes . . . . . . . . . . . . . . . 80210.7.3 Low-Temperature Activation . . . . . . . . . . . . . 80310.7.4 Process Selection Guide: Dopant Activation . . . . . 80310.7.5 Case Study: Rapid Thermal Anneal Versus

Conventional Thermal Anneal . . . . . . . . . . . . . 80410.8 Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . 805

10.8.1 Electrical Measurements . . . . . . . . . . . . . . . . 80610.8.2 Junction Staining Techniques . . . . . . . . . . . . . 80910.8.3 SIMS . . . . . . . . . . . . . . . . . . . . . . . . . . 81010.8.4 Case Study: Characterizing Junctions and

Diagnosing Implant Anomalies . . . . . . . . . . . . 810References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 812

11 Wafer Bonding . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81711.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 81711.2 Direct Wafer Bonding . . . . . . . . . . . . . . . . . . . . . . 821

11.2.1 Background and Physics . . . . . . . . . . . . . . . . 822

Contents xxv

11.2.2 Parameters for Successful Direct Wafer Bonding . . . 82411.2.2.1 Surface Roughness . . . . . . . . . . . . 82411.2.2.2 Waviness or Nanotopography . . . . . . . 82611.2.2.3 Wafer Shape . . . . . . . . . . . . . . . . 826

11.2.3 Recommendations for Successful DirectWafer Bonding . . . . . . . . . . . . . . . . . . . . . 826

11.2.4 Procedure of Direct Wafer Bonding . . . . . . . . . . 82811.2.4.1 Surface Preparation for Direct

Wafer Bonding . . . . . . . . . . . . . . 82811.2.4.2 Bonding Step – By Hand or by

Using a Wafer Bonding Tool . . . . . . . 83211.2.4.3 Basic Operation Principle of a

Wafer Bonding Tool . . . . . . . . . . . . 83511.2.4.4 Inspection Before Heat Treatment . . . . 83711.2.4.5 Thermal Treatment to Increase the

Bond Strength . . . . . . . . . . . . . . . 83811.2.4.6 Remaining Fabrication Process

for MEMS Device . . . . . . . . . . . . . 84011.2.5 Anodic Bonding . . . . . . . . . . . . . . . . . . . . 84011.2.6 Silicon–Glass Laser Bonding . . . . . . . . . . . . . 845

11.3 Wafer Bonding with Intermediate Material . . . . . . . . . . . 84611.3.1 Thermocompression Bonding . . . . . . . . . . . . . 84611.3.2 Eutectic Bonding . . . . . . . . . . . . . . . . . . . . 84611.3.3 Polymer Bonding . . . . . . . . . . . . . . . . . . . 847

11.4 Direct Comparison of Wafer Bonding Techniques . . . . . . . 85411.5 Bonding of Heterogeneous Compounds . . . . . . . . . . . . 85411.6 Wafer Bonding Process Integration . . . . . . . . . . . . . . . 856

11.6.1 Localized Wafer Bonding . . . . . . . . . . . . . . . 85611.6.2 Through Wafer via Technology . . . . . . . . . . . . 857

11.7 Characterization Techniques for Wafer Bonding . . . . . . . . 86311.8 Existing Wafer Bonding Infrastructure . . . . . . . . . . . . . 866

11.8.1 Wafer Bonding Services . . . . . . . . . . . . . . . . 86711.8.2 Bonding Tool Vendors . . . . . . . . . . . . . . . . . 867

11.8.2.1 Applied Microengineering Ltd(AML), UK . . . . . . . . . . . . . . . . 868

11.8.2.2 EV Group (EVG), Austria . . . . . . . . 86911.8.2.3 Mitsubishi Heavy Industries Ltd.

(MHI), Japan . . . . . . . . . . . . . . . 87011.8.2.4 SUSS MicroTec AG, Germany . . . . . . 871

11.9 Summary and Outlook . . . . . . . . . . . . . . . . . . . . . 872References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 873

12 MEMS Packaging Materials . . . . . . . . . . . . . . . . . . . . . 87912.1 MEMS Packages and Applications . . . . . . . . . . . . . . . 879

12.1.1 Packaging Classes . . . . . . . . . . . . . . . . . . . 880

xxvi Contents

12.1.2 MEMS Versus Microcircuit or IntegratedCircuit Packaging . . . . . . . . . . . . . . . . . . . 881

12.1.3 Application Drivers and Interfaces . . . . . . . . . . 88112.1.4 Interfaces to Other System Components . . . . . . . . 882

12.1.4.1 Power and Signals Interface . . . . . . . . 88312.1.4.2 Optical Interface . . . . . . . . . . . . . . 88312.1.4.3 Microfluidic Interface . . . . . . . . . . . 88412.1.4.4 Environmental Interface . . . . . . . . . . 885

12.2 Package Selection . . . . . . . . . . . . . . . . . . . . . . . . 88512.2.1 Metal . . . . . . . . . . . . . . . . . . . . . . . . . . 88612.2.2 Ceramic . . . . . . . . . . . . . . . . . . . . . . . . 88812.2.3 Plastic . . . . . . . . . . . . . . . . . . . . . . . . . 89112.2.4 Array Packaging Materials/Wafer Level Packaging . . 89212.2.5 Custom Packaging . . . . . . . . . . . . . . . . . . . 89212.2.6 Silicon Encapsulation . . . . . . . . . . . . . . . . . 89212.2.7 Glass Encapsulation . . . . . . . . . . . . . . . . . . 893

12.3 Lids and Lid Seals . . . . . . . . . . . . . . . . . . . . . . . . 89312.3.1 Optical Applications . . . . . . . . . . . . . . . . . . 894

12.4 Die Attach Materials and Processes . . . . . . . . . . . . . . . 89412.4.1 Conductive Die Attach . . . . . . . . . . . . . . . . . 89512.4.2 Metal-Filled Glasses and Epoxies . . . . . . . . . . . 89612.4.3 Other Die Attach Materials . . . . . . . . . . . . . . 89612.4.4 Flip-Chip Bonding . . . . . . . . . . . . . . . . . . . 89712.4.5 Tape Interconnects . . . . . . . . . . . . . . . . . . . 898

12.5 Wire Bonding . . . . . . . . . . . . . . . . . . . . . . . . . . 89912.5.1 Gold Wire Bonding . . . . . . . . . . . . . . . . . . 899

12.5.1.1 Au-Al System . . . . . . . . . . . . . . . 90012.5.1.2 Au-Ag System . . . . . . . . . . . . . . . 90112.5.1.3 Au-Au System . . . . . . . . . . . . . . . 90112.5.1.4 Au-Cu System . . . . . . . . . . . . . . . 901

12.5.2 Aluminum Systems . . . . . . . . . . . . . . . . . . 90112.5.2.1 Al-Al System . . . . . . . . . . . . . . . 90212.5.2.2 Al-Ag System . . . . . . . . . . . . . . . 90212.5.2.3 Al-Ni System . . . . . . . . . . . . . . . 902

12.5.3 Copper Systems . . . . . . . . . . . . . . . . . . . . 90212.6 Electrical Connection Processes . . . . . . . . . . . . . . . . 90212.7 Encapsulation . . . . . . . . . . . . . . . . . . . . . . . . . . 903

12.7.1 Polyurethane . . . . . . . . . . . . . . . . . . . . . . 90312.7.2 Polyimide . . . . . . . . . . . . . . . . . . . . . . . 90312.7.3 Polydimethylsiloxane (PDMS) . . . . . . . . . . . . 90412.7.4 Epoxy . . . . . . . . . . . . . . . . . . . . . . . . . 90412.7.5 Fluorocarbon (Polytetrafluoroethylene) . . . . . . . . 90512.7.6 Acrylic (PMMA) . . . . . . . . . . . . . . . . . . . . 90512.7.7 Parylene . . . . . . . . . . . . . . . . . . . . . . . . 90512.7.8 Liquid Crystal Polymer . . . . . . . . . . . . . . . . 906

Contents xxvii

12.8 Electrical and Thermal Requirements . . . . . . . . . . . . . . 90612.8.1 Electrical Considerations . . . . . . . . . . . . . . . 90612.8.2 Thermal Considerations . . . . . . . . . . . . . . . . 907

12.9 Hermeticity and Getter Materials . . . . . . . . . . . . . . . . 90812.9.1 Hermeticity and Pressurized Packaging . . . . . . . . 90812.9.2 Hermeticity and Vacuum Packaging . . . . . . . . . . 908

12.10 Quality and Reliability . . . . . . . . . . . . . . . . . . . . . 90812.10.1 MEMS Packaging Reliability Concerns . . . . . . . . 909

12.10.1.1 Thermal Effects . . . . . . . . . . . . . . 91012.10.1.2 Shock and Vibration . . . . . . . . . . . . 91112.10.1.3 Humidity . . . . . . . . . . . . . . . . . 911

12.10.2 MEMS Packaging and Quality Assurance . . . . . . . 91212.11 Case Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . 912

12.11.1 MEMS Accelerometer . . . . . . . . . . . . . . . . . 91412.11.2 Micro-mirror Array . . . . . . . . . . . . . . . . . . 91512.11.3 MEMS Microphone . . . . . . . . . . . . . . . . . . 91612.11.4 MEMS Shutters . . . . . . . . . . . . . . . . . . . . 916


13 Surface Treatment and Planarization . . . . . . . . . . . . . . . . 92513.1 Release Processes and Surface Treatments to Prevent Stiction . 926

13.1.1 Wet Chemical Release Techniques . . . . . . . . . . 92813.1.2 Dry Release Techniques . . . . . . . . . . . . . . . . 928

13.2 Surface Analysis . . . . . . . . . . . . . . . . . . . . . . . . 92913.2.1 Surface Chemical Composition . . . . . . . . . . . . 929

13.2.1.1 X-Ray PhotoelectronSpectroscopy (XPS or ESCA) . . . . . . 929

13.2.1.2 Scanning Auger ElectronSpectroscopy (AES) . . . . . . . . . . . . 930

13.2.1.3 Energy Dispersive X-RaySpectroscopy (EDS or EDX) . . . . . . . 931

13.2.1.4 Secondary Ion Mass Spectroscopy(SIMS) . . . . . . . . . . . . . . . . . . . 932

13.2.2 Surface Structure and Morphology . . . . . . . . . . 93213.2.2.1 Atomic Force Microscopy (AFM) . . . . 93213.2.2.2 Scanning Electron Microscopy (SEM) . . 933

13.2.3 Surface Energy Measurements . . . . . . . . . . . . . 93313.3 Adhesion and Friction of MEMS . . . . . . . . . . . . . . . . 934

13.3.1 Measurements of Adhesion and Friction . . . . . . . 93413.3.1.1 Cantilever Beam Array Technique . . . . 93413.3.1.2 Double-Clamped Beam Array Technique . 93513.3.1.3 Friction Test Structures . . . . . . . . . . 936

13.3.2 Effects of Surface Roughness . . . . . . . . . . . . . 93613.4 Chemical Modification of MEMS Surfaces . . . . . . . . . . . 936

xxviii Contents

13.4.1 Treatments for Low Surface Energy . . . . . . . . . . 93613.4.2 Siloxane and Silane Treatments . . . . . . . . . . . . 93713.4.3 Weakly Chemisorbed Surfactant Films . . . . . . . . 93813.4.4 Materials Properties and Process Selection Guidance . 939

13.5 Surface Considerations for Biological Applications . . . . . . 93913.5.1 Surface Modification Techniques . . . . . . . . . . . 94113.5.2 Modification of Pristine Substrate Surfaces . . . . . . 942

13.5.2.1 Plasma Treatment . . . . . . . . . . . . . 94213.5.2.2 Physical Adsorption . . . . . . . . . . . . 94313.5.2.3 Covalent Linkage . . . . . . . . . . . . . 943

13.5.3 Modification of Pre-treated Substrate Surfaces . . . . 94713.5.3.1 Chemistry of Hydroxyl Groups

(R-OH: Alcohols) . . . . . . . . . . . . . 94813.5.3.2 Chemistry of Amino Groups

(R–NH2: Amines) . . . . . . . . . . . . . 95013.5.3.3 Chemistry of Carboxyl Groups

(R–COOH: Carboxylic Acids) . . . . . . 95413.5.3.4 Chemistry of Mercapto Groups

(R–SH; Thiols) . . . . . . . . . . . . . . 95513.5.3.5 Chemistry of Formyl Groups

(R–CHO: Aldehydes) . . . . . . . . . . . 95913.5.4 Case Studies . . . . . . . . . . . . . . . . . . . . . . 962

13.5.4.1 Case Study 1: Promotion ofImmobilized Bioactive Proteins’Biological Activity . . . . . . . . . . . . 963

13.5.4.2 Case Study 2: EffectiveEnhancement of FluorescenceDetection Efficiency UsingAlternative Blocking Process inProtein Microarray Assays . . . . . . . . 964

13.5.4.3 Case Study 3: Control of SpecificReaction Kinetics InvolvingBifunctional Cross-Linkers . . . . . . . . 964

13.5.4.4 Case Study 4: SurfaceModification Using ElaboratelyDerivatized Functional Groups . . . . . . 967

13.5.4.5 Case Study 5: Surface Patterningby Microcontact Printing . . . . . . . . . 968

13.6 Surface Coating for Optical Applications . . . . . . . . . . . . 96913.6.1 Fundamentals of Optical Phenomena on

Surface Coatings . . . . . . . . . . . . . . . . . . . . 97013.6.1.1 Index Variation of Materials

Versus Wavelength [108] . . . . . . . . . 97013.6.1.2 Fresnel Equation for Reflection [108] . . . 97613.6.1.3 Principle of Antireflection (AR) [108] . . 978

Contents xxix

13.6.1.4 Principle of Absorption [108, 109] . . . . 98213.6.1.5 Surface Plasmon Resonance . . . . . . . 983

13.6.2 Material Properties and Process Selection Guidelines . 98513.6.2.1 High Reflection Applications . . . . . . . 98513.6.2.2 Antireflection Applications . . . . . . . . 98613.6.2.3 Considerations for Surface

Smoothness and Roughness . . . . . . . . 99013.6.2.4 Polymer Materials for Optical

Applications . . . . . . . . . . . . . . . . 99213.6.2.5 Surface Coatings for Polymer Materials . 99213.6.2.6 Applications for Light Absorption . . . . 998

13.7 Chemical Mechanical Planarization . . . . . . . . . . . . . . 100213.7.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . 1002

13.7.1.1 Chemistry of CMP . . . . . . . . . . . . 100213.7.1.2 Mechanics of CMP . . . . . . . . . . . . 1004

13.7.2 Applications . . . . . . . . . . . . . . . . . . . . . . 100813.7.2.1 Smoothing and Local Planarization . . . . 100913.7.2.2 Global Planarization . . . . . . . . . . . . 101013.7.2.3 Trench Fill . . . . . . . . . . . . . . . . . 1011

13.7.3 Pads and Slurry . . . . . . . . . . . . . . . . . . . . 101113.7.3.1 Summary of Slurry and Pad . . . . . . . . 1015

13.7.4 Polishing Considerations for Different Materials . . . 101513.7.4.1 Rate Comparison and Selectivity . . . . . 101513.7.4.2 Dielectrics . . . . . . . . . . . . . . . . . 102013.7.4.3 Metals . . . . . . . . . . . . . . . . . . . 102113.7.4.4 Polymers . . . . . . . . . . . . . . . . . 1023

13.7.5 Cleaning and Contamination Control . . . . . . . . . 102313.7.6 Case Study . . . . . . . . . . . . . . . . . . . . . . . 1025

13.7.6.1 Case Study 10: Magnetic Microdevice . . 102613.7.6.2 Case Study 11: A Drug-Delivery

Probe with an In-line Flow Meter . . . . . 102613.7.6.3 Case Study 12: Nanomechanical

Optical Devices . . . . . . . . . . . . . . 102913.7.6.4 Case Study 13: CMP of

SU-8/Permalloy Combination inMEMS Devices . . . . . . . . . . . . . . 1031

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1032

14 MEMS Process Integration . . . . . . . . . . . . . . . . . . . . . . 104514.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 104514.2 What Is Process Integration? . . . . . . . . . . . . . . . . . . 104614.3 What Is an Integrated MEMS Process? . . . . . . . . . . . . . 105014.4 Differences Between IC and MEMS Fabrication . . . . . . . . 105014.5 Challenges of MEMS Process Integration . . . . . . . . . . . 1052

14.5.1 Topography . . . . . . . . . . . . . . . . . . . . . . 1054

xxx Contents

14.5.2 Material Compatibility . . . . . . . . . . . . . . . . . 105614.5.3 Thermal Compatibility . . . . . . . . . . . . . . . . . 105714.5.4 Circuit/MEMS Partitioning of Fabrication . . . . . . 105814.5.5 Tooling Constraints . . . . . . . . . . . . . . . . . . 105914.5.6 Circuit/MEMS Physical Partitioning . . . . . . . . . 106014.5.7 Die Separation, Assembly and Packaging . . . . . . . 1062

14.6 How Is Process Integration Performed? . . . . . . . . . . . . . 106314.6.1 Integrated MEMS Process Integration Strategies . . . 1066

14.7 Design for Manufacturability . . . . . . . . . . . . . . . . . . 106714.7.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . 106714.7.2 Device Design for Manufacturability . . . . . . . . . 106814.7.3 Process Design for Manufacturability . . . . . . . . . 106914.7.4 Precision in MEMS Fabrication . . . . . . . . . . . . 107114.7.5 Package Design and Assembly . . . . . . . . . . . . 107414.7.6 System Design for Manufacturability . . . . . . . . . 107514.7.7 Environmental Variations . . . . . . . . . . . . . . . 107514.7.8 Test Variations . . . . . . . . . . . . . . . . . . . . . 107614.7.9 Recommendations Regarding Design for

Manufacturability . . . . . . . . . . . . . . . . . . . 107614.8 Review of Existing Process Technologies for MEMS . . . . . 1077

14.8.1 Process Selection Guide . . . . . . . . . . . . . . . . 107714.8.2 Nonintegrated MEMS Process Sequences . . . . . . . 1077

14.8.2.1 PolyMUMPSTM (MEMSCAP) . . . . . . 107714.8.2.2 Film Bulk Acoustic-Wave

Resonators (FBARs) (Avago) . . . . . . . 108214.8.2.3 Summit V (Sandia) . . . . . . . . . . . . 108614.8.2.4 Microphone (Knowles) . . . . . . . . . . 109014.8.2.5 Silicon Resonator (SiTime) . . . . . . . . 109414.8.2.6 Gyroscopes (Draper) . . . . . . . . . . . 109814.8.2.7 Bulk Accelerometer (STMicroelectronics) 109914.8.2.8 Pressure Sensor (NovaSensor) . . . . . . 110314.8.2.9 Microelectronics Wafer-Bonded

(Bulk) Accelerometer Process(Ford Microelectronics) . . . . . . . . . . 1106

14.8.2.10 Single-Crystal Reactive Etchingand Metallization (SCREAM)(Cornell University) . . . . . . . . . . . . 1108

14.8.2.11 High-Aspect-Ratio CombinedPoly and Single-Crystal Silicon(HARPSS) MEMS Technology(University of Michigan andGeorgia Tech) . . . . . . . . . . . . . . . 1109

14.8.2.12 Hybrid MEMS (Infotonics) . . . . . . . . 111114.8.2.13 Silicon-On-Glass (University

of Michigan) . . . . . . . . . . . . . . . . 1115

Contents xxxi

14.8.2.14 SOI MUMPSTM (MEMSCap) . . . . . . 111814.8.2.15 LIGA (CAMD, etc.) . . . . . . . . . . . . 111914.8.2.16 RF Switch (MEMStronics) . . . . . . . . 112114.8.2.17 MetalMUMPSTM (MEMSCap) . . . . . . 112414.8.2.18 aMEMSTM (Teledyne) . . . . . . . . . . 112614.8.2.19 Plastic MEMS (University of Michigan) . 113014.8.2.20 Wafer-Level Packaging (ISSYS) . . . . . 1132

14.8.3 Review of Integrated CMOS MEMS ProcessTechnologies . . . . . . . . . . . . . . . . . . . . . . 113414.8.3.1 iMEMS – Analog Devices . . . . . . . . 113414.8.3.2 DLP (Texas Instruments) . . . . . . . . . 113814.8.3.3 Integrated MEMS Pressure Sensor

(Freescale) . . . . . . . . . . . . . . . . . 114114.8.3.4 Thermal Inkjet Printhead (Xerox) . . . . . 114414.8.3.5 Microbolometer (Honeywell) . . . . . . . 114914.8.3.6 ASIMPS and ASIM-X (CMU) . . . . . . 115314.8.3.7 Integrated CMOS+RF MEMS

Process (wiSpry) . . . . . . . . . . . . . 115414.8.3.8 Integrated SiGe MEMS (UCB) . . . . . . 115614.8.3.9 Integrated SUMMiT (Sandia) . . . . . . . 1158

14.9 The Economic Realities of MEMS Process Development . . . 116114.9.1 Cost and Time for MEMS Development . . . . . . . 116114.9.2 Production Cost Models . . . . . . . . . . . . . . . . 1166

14.9.2.1 MEMS Hybrid Versus IntegratedMEMS Production Cost . . . . . . . . . . 1166

14.10 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . 1176References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1177

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1183

This is Blank Page Integra xxxii

Contributors

David P. Arnold Department of Electrical and Computer Engineering, Universityof Florida, Gainesville, FL, USA, [email protected]

Stephen F. Bart Micromachined Products Division, Analog Devices, Inc.,Norwood, MA, USA, [email protected]

William Benard Sensors and Electron Devices Directorate, U.S. Army ResearchLaboratory, Adelphi, MD, USA, [email protected]

David W. Burns Burns Engineering, San Jose, CA, USA, [email protected]

Carlo Carraro Department of Chemical Engineering, University of California atBerkeley, Berkeley, CA, USA, [email protected]

Li Chen Department of Electrical Engineering and Computer Science, CaseWestern Reserve University, Cleveland, OH, USA, [email protected]

Shawn J. Cunningham WiSpry, Inc., Irvine, CA, USA,[email protected]

Ann Garrison Darrin The Johns Hopkins University Applied PhysicsLaboratory, Laurel, MD, USA, [email protected]

Reza Ghodssi Department of Electrical and Computer Engineering, Institute forSystems Research, MEMS Sensors and Actuators Laboratory, University ofMaryland, College Park, Maryland, USA, [email protected]

Yoichi Haga Graduate School of Biomedical Engineering, Tohoku University,Sendai, Japan, [email protected]

Daniel R. Hines Laboratory for Physical Sciences, College Park, MD, USA,[email protected]

Michael A. Huff MEMS and Nanotechnology Exchange, Reston, VA, USA,[email protected]

Mario Kupnik Chair of General Electrical Engineering and MeasurementTechniques, Brandenburg University of Technology, Cottbus, Brandenburg,Germany, [email protected]

xxxiii

xxxiv Contributors

Tina L. Lamers Avago Technologies, Fort Collins, CO, USA,[email protected]

Franz Lärmer Robert Bosch GmbH, Corporate Research Microsystems,Stuttgart, Germany, [email protected]

Yongqing Lan Department of Chemistry, Clarkson University, Potsdam, NY,USA, [email protected]

Pinyen Lin Touch Micro-system Technology Corp., Taoyuan; Walsin LihwaCorporation, Taipei, Taiwan, [email protected]

Roya Maboudian Department of Chemical Engineering, University of Californiaat Berkeley, Berkeley, CA, USA, [email protected]

Ellis Meng Departments of Biomedical and Electrical Engineering, University ofSouthern California, Los Angeles, CA, USA, [email protected]

Takashi Mineta Graduate School of Science and Engineering, YamagataUniversity, Yonezawa, Japan, [email protected]

Lance A. Mosher Lockheed Martin Space Systems Company, Newtown, PA,USA, [email protected]

Robert Osiander The Johns Hopkins University Applied Physics Laboratory,Laurel, MD, USA, [email protected]

Ronald G. Polcawich Micro & Nano Electronic Materials & Devices Branch, USArmy Research Laboratory, Adelphi, MD, USA, [email protected]

Beth L. Pruitt Department of Mechanical Engineering, Stanford University,Stanford, CA, USA, [email protected]

Jeffrey S. Pulskamp Micro & Nano Electronic Materials & Devices Branch, USArmy Research Laboratory, Adelphi, MD, USA, [email protected]

Alan D. Raisanen IT Collaboratory, Rochester Institute of Technology,Rochester, NY, USA, [email protected]

Robert C. Roberts Department of Electrical Engineering and Computer Science,Case Western Reserve University, Cleveland, OH, USA, [email protected]

Monika Saumer Department of Microsystems Technology, University ofApplied Sciences, Kaiserslautern, Germany, [email protected]

Nathan P. Siwak Department of Electrical and Computer Engineering, Institutefor Systems Research, MEMS Sensors and Actuators Laboratory, University ofMaryland, College Park, Maryland, USA, [email protected]

Srinivas Tadigadapa Department of Electrical Engineering, The PennsylvaniaState University, University Park, PA, USA; Materials Research Institute, ThePennsylvania State University, University Park, PA, USA, [email protected]

Contributors xxxv

Fan-Gang Tseng Department of Engineering and System Science, NationalTsing Hua University, Hsinchu, Taiwan, [email protected]

Pen-Cheng Wang Department of Engineering and System Science, NationalTsing Hua University, Hsinchu, Taiwan, [email protected]

Yong-Kyu Yoon Department of Electrical Engineering, University at Buffalo, TheState University of New York, Buffalo, NY, USA, [email protected]

Xin Zhang Department of Mechanical Engineering, Boston University, Boston,MA, USA, [email protected]

Christian A. Zorman Department of Electrical Engineering and ComputerScience, Case Western Reserve University, Cleveland, OH, USA, [email protected]

Documents

MEMS Materials and Processes Handbook - Home - …978-0-387-47318-5/1.pdf · MEMS Materials and Processes Handbook 123. Editors ... microturbine, Analog Devices ... culminated in