Tài liệu An Introduction to Microelectromechanical Systems Engineering P1 pdf

Written in a no-nonsense, clear style, the book bringsthe practicing engineer and student alike to an understanding of how MEMS aredesigned and fabricated.. at Stanford University, Dr.Ma

An Introduction to Microelectromechanical Systems Engineering

Second Edition

For a listing of recent titles in the Artech House Microelectromechanical

Systems (MEMS) Series, turn to the back of this book.

An Introduction to Microelectromechanical Systems Engineering

Second Edition

Nadim Maluf Kirt Williams

Artech House, Inc.

Boston • London www.artechhouse.com

Library of Congress Cataloging-in-Publication Data

A catalog record for this book is available from the U.S Library of Congress

British Library Cataloguing in Publication Data

Cover design by Igor Valdman

© 2004 ARTECH HOUSE, INC.

685 Canton Street

Norwood, MA 02062

All rights reserved Printed and bound in the United States of America No part of this bookmay be reproduced or utilized in any form or by any means, electronic or mechanical, includ-ing photocopying, recording, or by any information storage and retrieval system, withoutpermission in writing from the publisher

All terms mentioned in this book that are known to be trademarks or service marks havebeen appropriately capitalized Artech House cannot attest to the accuracy of this informa-tion Use of a term in this book should not be regarded as affecting the validity of any trade-mark or service mark

International Standard Book Number: 1-58053-590-9

10 9 8 7 6 5 4 3 2 1

To our families

Tanya, Ella, and Jad Erika, Gordon, Brynn, and Reed

.

CHAPTER 2

Gallium Arsenide and Other Group III-V Compound Semiconductors 22

vii

Grinding, Polishing, and Chemical-Mechanical Polishing 57

Combining Silicon Fusion Bonding with Reactive Ion Etching 71

CHAPTER 4

MEM Structures and Systems in Industrial and Automotive Applications 79

Projection Display with the Digital Micromirror DeviceTM

135

Beam-Steering Micromirror for Photonic Switches and Cross Connects 156

CHAPTER 6

The Structure of DNA 172

CHAPTER 7

Passive Electrical Components: Capacitors and Inductors 190Quality Factor and Parasitics in Passive Components 190

CHAPTER 8

Types of Packaging Solutions 233

.

According to my best recollection, the acronym for microelectromechanical systems(MEMS) was officially adopted by a group of about 80 zealots at a crowded meet-ing in Salt Lake City in 1989 called the Micro Tele-Operated Robotics Workshop Iwas there to present an invited paper that claimed MEMS should be used to fabri-cate resonant structures for the purposes of timekeeping, and I was privileged to bepart of this group of visionaries for one and a half exciting days The proceedingsmay not be in print any longer However, I recall that they were given an Institute ofElectrical and Electronic Engineers (IEEE) catalog number of 89TH0249-3 Discus-sion at the workshop about the name of this new field of research raged for over anhour, and several acronyms were offered, debated, and rejected When the dust set-tled, I recall that Professor Roger Howe of the University of California at Berkeleystood up and announced, “Well, then, the name is MEMS.” In this way, the groupcame to consensus The research they conducted, unique to any currently being con-ducted in the United States (or the world for that matter) would hereafter be known

as “MEMS.”

In those early, heady, exciting, and terribly uncertain days, many issues facedthose in the nascent field that researchers today would find hard to remember Forexample, our hearty band constantly worried if any scholarly journal would publishthe papers we wrote Sources of research funding were hard to find and difficult tomaintain MEMS fabrication was itself a major issue Topics of conversation werefrequently about the nature, properties, and standardization of the polysilicon thatthe pioneering band of researchers was using to demonstrate the early, elementarystructures of the day Even the most daring and idealistic of students occasionallyturned down the offer to work with the faculty of that era: the work sometimesappeared too farfetched for the taste of even the green-eyed zealots among thegraduate student population

In the 10 years since the momentous events of that watershed workshop, theNational Science Foundation (NSF) funded a set of MEMS projects under its

“Emerging Technologies Initiative,” headed at the time by George Hazelrigg NSFfunding continues to this day The Defense Advanced Projects Research Agency(DARPA) put nearly $200 million into MEMS research Numerous MEMS journalshave sprung up, and the rate of filing of MEMS patents has reached over 160 percalendar year in 1997 The skeptics that predicted the collapse of the field in 1990are now confronted with the fact that, in 1997, 80 U.S were companies in theMEMS field The combined total world market of MEMS reached approximately

$2 billion as well In addition, the most conservative market studies predict a worldMEMS market in excess of $8 billion in 2003 In a phrase, MEMS has arrived

xiii

Despite all the rosy news, there remain significant challenges facing the MEMSfield One of these I call the challenge of the “500 MEMS Companies” and the other,the “10,000 MEMS Designers.” For the field to fully take root and become ubiqui-tous, there must be an unprecedented training of tens of thousands of MEMS engi-neers Already, the demand for MEMS experts has far outstripped the ability ofacademia to train them The only hope is for existing engineers to learn the basics ofMEMS and then go up the MEMS learning curve in the traditional way (i.e., learn-ing by doing).

Here is where this book plays an important, essential role on the national stage

Dr Nadim Maluf has put together one of the finest MEMS primers that you mayfind on the bookshelf today Written in a no-nonsense, clear style, the book bringsthe practicing engineer and student alike to an understanding of how MEMS aredesigned and fabricated Dr Maluf’s book concentrates mostly on how to designand manufacture MEMS This is to be expected of Dr Maluf, who has impeccableMEMS credentials Trained in MEMS for his Ph.D at Stanford University, Dr.Maluf has spent his postdoctoral career as a practicing MEMS engineer and man-ager at Lucas NovaSensor, one of the early MEMS companies in the field His indus-trial career has been focused both on bringing MEMS products successfully tomarket and on defending his company’s market share against encroachment byother technologies Because this book is written from Dr Maluf’s practical perspec-tive, this volume is sure to have lasting value to the myriad of engineers and execu-tives who are struggling to find a way into the field of MEMS This book also willserve as a useful resource for those already in the field who wish to broaden theirexpertise in MEMS fabrication When I reviewed the manuscript, I was ready tooffer Dr Maluf a great deal of suggestions and corrections I was quite humbled torealize that, instead, I was eager to have a copy of the new book on my own shelf Itwill serve as a reference for not only myself, but also the students and engineers whofrequently ask me, “What book should I buy to learn how to make MEMS?”

Albert (“Al”) P Pisano, Ph.D MEMS Program Manager

DARPA

The past few years have witnessed an increasing maturity of the MEMS industryand a rapid introduction of new products addressing applications ranging from bio-chemical analysis to fiber-optic telecommunications The market size for MEMSproducts has doubled in the past 5 years and is projected to grow at this fast rate forthe foreseeable future The corresponding technology has enjoyed a fast pace ofdevelopment and has rapidly spread to institutions and companies on all inhabitedcontinents A search of the keyword MEMS in all granted patents in the UnitedStates since 1998 returns nearly 4,000 patents and references Many devices haveleft universities to go into commercial development, and several have reached thestage of becoming products It is therefore appropriate to extensively revise the text

to incorporate advances in the field, new products, as well as suggestions from thereaders

As we revised the original text and added substantial new material, we strived toretain the style characteristic of an introductory book intended for a broad audience

of scientists, engineers, students, and business executives This revised edition tinues to assume that the reader has no prior experience in MEMS technology butdoes possess an understanding of basic scientific concepts equivalent to first-yearcollege physics and chemistry The objective remained to introduce a select number

con-of representative demonstrators that are now or are soon to be commercially able We added many more illustrations and pictures to aid the reader in developing

avail-a favail-amiliavail-arity with the technology We avail-also included throughout the text more pravail-acti-cal tidbits that are useful to those who wish to apply this technology to their needs

practi-In this revision, we have expanded on the fabrication processes, adding newmethods and materials The advantages and limitations of many micromachinedstructures are covered in more detail We divided the chapter on commercial struc-tures into four chapters, each focusing on a specific application, and then expandedeach chapter with appropriate material covering new technical developments andproducts Chapter 4 is now specific to automotive and industrial applications, cov-ering traditional products, such as pressure sensors, accelerometers, and yaw-ratesensors, and new emerging products in valving and pumping Chapter 5 now coversthe applications of MEMS in photonics, including displays, optical sensors, andnew products that are now common in fiber-optic telecommunications The focus

of Chapter 6 is on applications in life sciences, with emphasis on new products anddevelopments specific to biochemical analysis and microfluidics With the emer-gence of wireless and radio frequency (RF) as a new market for MEMS technology,

we dedicated Chapter 7 to describe recent developments and introductions in thispromising area In Chapters 4 through 7, we expanded where appropriate on the

xv

application and on the system that includes the MEMS product We also expandedthe material in Chapter 8 on packaging to include packaging of optical MEMS prod-ucts and added an entirely new section on reliability and quality assurance Weadded several references to each chapter to direct the advanced reader to the source

of the material We also expanded the glossary to assist the novice in understandingand relating to a new terminology

Many people provided us technical information and materials specifically forthe second edition of this book We thank Bardia Pezeshki of Santur Corporation;John (Hal) Jerman of Iolon; Asif Godil of Lightconnect; Greg Ortiz of Surface Tech-nology Systems; Bonnie Gray; Greg Jepson of Bullen Ultrasonics; Chris Bang andDen Feinberg of Microfabrica; Malcom Gower of Exitech; Amy Wang; Brian Paegel

of The Scripps Research Institute; Carol Schembri and John Larson of Agilent nologies; Didier Lacroix and Ken Cioffi of Discera; Michael Cohn of MicroAssem-bly; Nelson Fuller of Alumina Micro; and Stephen Durant and Christopher Eide ofMorrison and Foerster Evan Green and Carter Hand of New Focus were kindenough to review portions of the manuscript Thanks go to our editor, Mark Walsh,for his unwavering support Kirt Williams further thanks his former graduate advi-sor, Professor Richard S Muller, for having such a profound effect on his life forintroducing him to MEMS

“It was the best of times, it was the worst of times, it was the age of wisdom, it was

the age of foolishness…” from A Tale of Two Cities by Charles Dickens, engraved

on a thin silicon nitride membrane The entire page measures a mere 5.9µm on a

side, sufficiently small that 60,000 pages—equivalent to the Encyclopedia nica—can fit on a pinhead The work, by T Newman and R F W Pease of Stan-

Britan-ford University, won the Feynman challenge in 1985

(Courtesy of: Engineering & Science, California Institute of Technology, Pasadena, California.)

.

Preface to First Edition

I stood a few years ago before an audience at a customer’s facility explaining themerits of micromachining technology The small conference room was packed, andall ears were attentive Everyone was eager to learn about this mysterious buzz-word, “MEMS.” Many in the audience were nodding in a sign of comprehension,but the gazed looks on many faces betrayed them This experience is not unique;rather, it repeats itself frequently in auditoriums around the world The technology

is simply too broad to be explained in a short lecture Many technical managers,engineers, scientists, and even engineering students with little or no prior experience

in microelectromechanical systems are showing a keen interest in learning aboutthis emerging technology This book is written for these individuals

I sought in this book to introduce the technology by describing basic tion processes and select examples of devices and microsystems that are either com-mercially available or show great promise in becoming products in the nearfuture—practical examples from the “real world.” The objective is to provide a set

fabrica-of representative cases that can give the reader a global understanding fabrica-of the nology’s foundations and a sense of its diversity The text describes the basic opera-tion and fabrication of many devices, along with packaging requirements Inspired

tech-by the adage “a picture is worth a thousand words,” I have included numerousdescriptive schematic illustrations It is my hope that scanning these illustrationswill aid the reader in quickly developing a basic familiarity with the technology.Suggestions at the end of each chapter for further reading and an extensive glossaryshould supplement the main text

The following paragraphs present an overview of each chapter in the book

Chapter 1—MEMS: A Technology from Lilliput This introductory chapter

defines the scope of the technology and the applications it addresses A short sis of existing markets and future opportunities is also included

analy-Chapter 2—The Sandbox: Materials for MEMS This chapter reviews the

properties of materials common in micromachining The emphasis is on siliconand materials that can be readily deposited as thin films on silicon substrates.Three physical effects—piezoresistivity, piezoelectricity, and thermoelectricity—aredescribed in some detail

Chapter 3—The Toolbox: Processes for Micromachining Various fabrication

techniques used in semiconductor manufacturing and micromachining are duced These include a number of deposition and etch methods, as well as lithogra-phy The discussion on etch methods covers the topics of anisotropic etching,dependence on crystallographic planes, and deep reactive ion etching Three com-plete manufacturing process flows are described at the end

intro-xix

Chapter 4—The Gearbox: Commercial MEM Structures and Systems This

chapter includes descriptions of a select list of commercially availablemicromachined sensors and actuators The discussion includes the basic principle ofoperation and a corresponding fabrication process for each device Among thedevices are pressure and inertial sensors, a microphone, a gas sensor, valves, aninfrared imager, and a projection display system

Chapter 5—The New Gearbox: A Peek into the Future The discussion in this

chapter centers on devices and systems still under development but with significantpotential for the future These include biochemical and genetic analysis systems,high-frequency components, display elements, pumps, and optical switches

Chapter 6—The Box: Packaging for MEMS The diverse packaging

require-ments for MEMS are reviewed in this chapter The basic techniques of packagingsensors and actuators are also introduced A few nonproprietary packaging solu-tions are described

The writing of a book usually relies on the support and encouragement of leagues, friends, and family members This book is no exception I am grateful to AlPisano for his general support and for recognizing the value of an introductory book

col-on MEMS I would like to thank Greg Kovacs, Kirt Williams, and Denise Salles forreading the manuscript and providing valuable feedback They left an indelible mark

of friendship on the pages of the book I am thankful to many others for their ments, words of encouragement, and contributions To Bert van Drieënhuizen,Dominik Jaeggi, Bonnie Gray, Jitendra Mohan, John Pendergrass, Dale Gee, TonyFlannery, Dave Borkholder, Sandy Plewa, Andy McQuarrie, Luis Mejia, StefaniYee, Viki Williams, and the staff at NovaSensor, I say, “Thank you!” Jerry Gist’sartistic talents proved important in designing the book cover For those I inadver-tently forgot to mention, please forgive me I am also grateful to DARPA for provid-ing partial funding under contract N66001-96-C-8631 Last, but not least, wordscannot duly express my gratitude and love to my wife, Tanya She taught me overthe course of writing this book the true meaning of love, patience, dedication, under-standing, and support I set out in this book to teach technology, but I finished learn-ing from her about life

com-Nadim Maluf August 1999