Ghodssi R., Lin P., MEMS Materials and Processes Handbook
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xxx Contents
14.5.2 Material Compatibility ................. 1056
14.5.3 Thermal Compatibility ................. 1057
14.5.4 Circuit/MEMS Partitioning of Fabrication . . .... 1058
14.5.5 ToolingConstraints .................. 1059
14.5.6 Circuit/MEMS Physical Partitioning . ........ 1060
14.5.7 Die Separation, Assembly and Packaging . . . .... 1062
14.6 How Is Process Integration Performed? ............. 1063
14.6.1 Integrated MEMS Process Integration Strategies . . . 1066
14.7 Design for Manufacturability .................. 1067
14.7.1 Overview........................ 1067
14.7.2 Device Design for Manufacturability . ........ 1068
14.7.3 Process Design for Manufacturability . ........ 1069
14.7.4 PrecisioninMEMSFabrication............ 1071
14.7.5 Package Design and Assembly ............ 1074
14.7.6 System Design for Manufacturability . ........ 1075
14.7.7 EnvironmentalVariations ............... 1075
14.7.8 TestVariations..................... 1076
14.7.9 Recommendations Regarding Design for
Manufacturability . .................. 1076
14.8 Review of Existing Process Technologies for MEMS . .... 1077
14.8.1 Process Selection Guide . . . ............. 1077
14.8.2 Nonintegrated MEMS Process Sequences . . . .... 1077
14.8.2.1 PolyMUMPS
TM
(MEMSCAP)...... 1077
14.8.2.2 Film Bulk Acoustic-Wave
Resonators (FBARs) (Avago) . . . .... 1082
14.8.2.3 Summit V (Sandia) ............ 1086
14.8.2.4 Microphone (Knowles) . . ........ 1090
14.8.2.5 Silicon Resonator (SiTime) ........ 1094
14.8.2.6 Gyroscopes (Draper) . . . ........ 1098
14.8.2.7 Bulk Accelerometer (STMicroelectronics) 1099
14.8.2.8 Pressure Sensor (NovaSensor) . . .... 1103
14.8.2.9 Microelectronics Wafer-Bonded
(Bulk) Accelerometer Process
(FordMicroelectronics).......... 1106
14.8.2.10 Single-Crystal Reactive Etching
and Metallization (SCREAM)
(CornellUniversity)............ 1108
14.8.2.11 High-Aspect-Ratio Combined
Poly and Single-Crystal Silicon
(HARPSS) MEMS Technology
(University of Michigan and
Georgia Tech) . . ............. 1109
14.8.2.12 HybridMEMS(Infotonics)........ 1111
14.8.2.13 Silicon-On-Glass (University
ofMichigan)................ 1115
Contents xxxi
14.8.2.14 SOI MUMPS
TM
(MEMSCap) ...... 1118
14.8.2.15 LIGA(CAMD,etc.)............ 1119
14.8.2.16 RFSwitch(MEMStronics) ........ 1121
14.8.2.17 MetalMUMPS
TM
(MEMSCap)...... 1124
14.8.2.18 aMEMS
TM
(Teledyne) . . ........ 1126
14.8.2.19 Plastic MEMS (University of Michigan) . 1130
14.8.2.20 Wafer-Level Packaging (ISSYS) . .... 1132
14.8.3 Review of Integrated CMOS MEMS Process
Technologies ...................... 1134
14.8.3.1 iMEMS–AnalogDevices ........ 1134
14.8.3.2 DLP(TexasInstruments) ......... 1138
14.8.3.3 Integrated MEMS Pressure Sensor
(Freescale)................. 1141
14.8.3.4 Thermal Inkjet Printhead (Xerox) . .... 1144
14.8.3.5 Microbolometer (Honeywell) . . . .... 1149
14.8.3.6 ASIMPSandASIM-X(CMU) ...... 1153
14.8.3.7 Integrated CMOS+RF MEMS
Process (wiSpry) ............. 1154
14.8.3.8 IntegratedSiGeMEMS(UCB)...... 1156
14.8.3.9 Integrated SUMMiT (Sandia) . . . .... 1158
14.9 The Economic Realities of MEMS Process Development . . . 1161
14.9.1 CostandTimeforMEMSDevelopment ....... 1161
14.9.2 Production Cost Models . . . ............. 1166
14.9.2.1 MEMS Hybrid Versus Integrated
MEMS Production Cost . . ........ 1166
14.10 Conclusions ........................... 1176
References . . . ............................ 1177
Index ..................................... 1183
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Contributors
David P. Arnold Department of Electrical and Computer Engineering, University
of Florida, Gainesville, FL, USA, darnold@ufl.edu
Stephen F. Bart Micromachined Products Division, Analog Devices, Inc.,
Norwood, MA, USA, stephen.bart@analog.com
William Benard Sensors and Electron Devices Directorate, U.S. Army Research
Laboratory, Adelphi, MD, USA, william.benard1@us.army.mil
David W. Burns Burns Engineering, San Jose, CA, USA, dwburns@pacbell.net
Carlo Carraro Department of Chemical Engineering, University of California at
Berkeley, Berkeley, CA, USA, carraro@berkeley.edu
Li Chen Department of Electrical Engineering and Computer Science, Case
Western Reserve University, Cleveland, OH, USA, li.chen@case.edu
Shawn J. Cunningham WiSpry, Inc., Irvine, CA, USA,
shawn.cunningham@wispry.com
Ann Garrison Darrin The Johns Hopkins University Applied Physics
Laboratory, Laurel, MD, USA, ann.darrin@jhuapl.edu
Reza Ghodssi Department of Electrical and Computer Engineering, Institute for
Systems Research, MEMS Sensors and Actuators Laboratory, University of
Maryland, College Park, Maryland, USA, ghodssi@umd.edu
Yoichi Haga Graduate School of Biomedical Engineering, Tohoku University,
Sendai, Japan, haga@bme.tohoku.ac.jp
Daniel R. Hines Laboratory for Physical Sciences, College Park, MD, USA,
hines@lps.umd.edu
Michael A. Huff MEMS and Nanotechnology Exchange, Reston, VA, USA,
mhuff@mems-exchange.org
Mario Kupnik Chair of General Electrical Engineering and Measurement
Techniques, Brandenburg University of Technology, Cottbus, Brandenburg,
Germany, kupnik@tu-cottbus.de
xxxiii
xxxiv Contributors
Tina L. Lamers Avago Technologies, Fort Collins, CO, USA,
tina.lamers@avagotech.com
Franz Lärmer Robert Bosch GmbH, Corporate Research Microsystems,
Stuttgart, Germany, franz.laermer@de.bosch.com
Yongqing Lan Department of Chemistry, Clarkson University, Potsdam, NY,
USA, lany@clarkson.edu
Pinyen Lin Touch Micro-system Technology Corp., Taoyuan; Walsin Lihwa
Corporation, Taipei, Taiwan, pinyen_lin@alum.mit.edu
Roya Maboudian Department of Chemical Engineering, University of California
at Berkeley, Berkeley, CA, USA, maboudia@berkeley.edu
Ellis Meng Departments of Biomedical and Electrical Engineering, University of
Southern California, Los Angeles, CA, USA, ellis.meng@usc.edu
Takashi Mineta Graduate School of Science and Engineering, Yamagata
University, Yonezawa, Japan, mineta-t@yz.yamagata-u.ac.jp
Lance A. Mosher Lockheed Martin Space Systems Company, Newtown, PA,
USA, lance.mosher@gmail.com
Robert Osiander The Johns Hopkins University Applied Physics Laboratory,
Laurel, MD, USA, robert.osiander@jhuapl.edu
Ronald G. Polcawich Micro & Nano Electronic Materials & Devices Branch, US
Army Research Laboratory, Adelphi, MD, USA, ronald.g.polcawich@us.army.mil
Beth L. Pruitt Department of Mechanical Engineering, Stanford University,
Stanford, CA, USA, pruitt@stanford.edu
Jeffrey S. Pulskamp Micro & Nano Electronic Materials & Devices Branch, US
Army Research Laboratory, Adelphi, MD, USA, jeffrey.pulskamp1@us.army.mil
Alan D. Raisanen IT Collaboratory, Rochester Institute of Technology,
Rochester, NY, USA, adremc@rit.edu
Robert C. Roberts Department of Electrical Engineering and Computer Science,
Case Western Reserve University, Cleveland, OH, USA, robert.roberts@case.edu
Monika Saumer Department of Microsystems Technology, University of
Applied Sciences, Kaiserslautern, Germany, monika.saumer@fh-kl.de
Nathan P. Siwak Department of Electrical and Computer Engineering, Institute
for Systems Research, MEMS Sensors and Actuators Laboratory, University of
Maryland, College Park, Maryland, USA, npsiwak@lps.umd.edu
Srinivas Tadigadapa Department of Electrical Engineering, The Pennsylvania
State University, University Park, PA, USA; Materials Research Institute, The
Pennsylvania State University, University Park, PA, USA, srinivas@engr.psu.edu
Contributors xxxv
Fan-Gang Tseng Department of Engineering and System Science, National
Tsing Hua University, Hsinchu, Taiwan, fangang@ess.nthu.edu.tw
Pen-Cheng Wang Department of Engineering and System Science, National
Tsing Hua University, Hsinchu, Taiwan, wangpc@ess.nthu.edu.tw
Yong-Kyu Yoon Department of Electrical Engineering, University at Buffalo, The
State University of New York, Buffalo, NY, USA, ykyoon@buffalo.edu
Xin Zhang Department of Mechanical Engineering, Boston University, Boston,
MA, USA, xinz@bu.edu
Christian A. Zorman Department of Electrical Engineering and Computer
Science, Case Western Reserve University, Cleveland, OH, USA, caz@case.edu
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Chapter 1
The MEMS Design Process
Tina L. Lamers and Beth L. Pruitt
Abstract Today’s ubiquitous commercial MEMS devices, such as accelerometers,
inkjet printheads, pressure sensors, and micromirror arrays, took 10–20 years from
first report to commercialization. Timelines from initial development through prod-
uct release for some successful MEMS commercial products have been getting
shorter as MEMS technologies have matured. Companies can no longer afford such
long development times. MEMS development time can be systematically short-
ened through the use of structured design methods. This chapter overviews the
design process and design methods, illustrating structured design methods through
case studies. We suggest reading this chapter prior to getting into the details of
materials and process seletion, and applying the methods described to shorten
development time.
1.1 Introduction
Innovation still thrives, but MEMS designers increasingly leverage existing pro-
cesses and technologies in new products. Figure 1.1 shows the timelines of some
of the earliest MEMS technologies from initial reports, typically based on aca-
demic research, to launch as a mature commercial product. Figure 1.1 also includes
representative images of modern products reprinted with permission of the fol-
lowing companies: a digital pressure sensor by Freescale incorporates calibration
and compensation in a paired ASIC; an inkjet cartridge by Hewlett Packard
uses integrated circuitry in the nozzle region of thermal inkjet chip to control
droplet size and placement; high aspect ratio MEMS accelerometers by Freescale
provide on-axis stability; the digital micro-mirror for digital light projection by
Texas Instruments led a revolution in optical MEMS and light switching products;
Seacoast Science’s micro gas chromatograph sensor arrays use micromachined,
T.L. Lamers (B)
Avago Technologies, Fort Collins, CO, USA
e-mail: tina.lamers@avagotech.com
1
R. Ghodssi, P. Lin (eds.), MEMS Materials and Processes Handbook,
MEMS Reference Shelf, DOI 10.1007/978-0-387-47318-5_1,
C
Springer Science+Business Media, LLC 2011
2 T.L. Lamers and B.L. Pruitt
Fig. 1.1 Timeline of research and development cycles from first research reports to first commer-
cialization of several MEMS products. Modified figure, used with permission of Kurt Petersen.
Product images used with permission of the copyright holders as indicated above
parallel-plate polysilicon capacitors filled with polymers; microfluidic chips by
Caliper integrate sampling, separations, and analysis; film bulk acoustic resonators
(FBAR) by Avago Technologies revolutionized electronic filter design for the hand-
set market; encapsulated resonator timekeeping references by SiTime compete with
quartz; micromachined MM3 electronic stability program (ESP) gyroscopic sen-
sor cluster by Bosch enables consumer and automotive orientation sensing; SiSonic
microphones by Knowles dramatically enhance the manufacturability of printed cir-
cuit boards compared to polymeric electret condenser microphones. This historical
timeline is far too long for most new products; companies cannot afford to fund
development efforts that may not be profitable in one or two decades. However,
MEMS product placement can be improved and development time can be sys-
tematically shortened through the use of structured design methods. This chapter
overviews the design process and design methods, illustrating structured design
1 The MEMS Design Process 3
methods through case s tudies. We suggest reading this chapter prior to getting into
the details of materials and process selection, and applying the methods described
to shorten development time.
First, we review what is arguably the beginning of MEMS history. Piezoresistive
silicon strain gauges were introduced in the late 1950s by Kulite Semiconductor,
Bell Lab’s first licensee of patents on semiconductor piezoresistance reported in
1954 [1]. Kulite’s strain gauges represent some of the first commercially distributed
microelectromechanical systems (MEMS) [2]. Although research on microsystems
grew over the ensuing decades [3, 4] relatively few became widespread commercial
products until manufacturing advances driven by the integrated circuits industry
were widely available; Fig. 1.2 details several time points of developments in the
integrated circuits industry that advanced piezoresistive MEMS design.
Accelerated product development cycles can be expected if designers leverage
existing knowledge of materials and processes to simultaneously design new trans-
ducers. For example, Fig. 1.1 shows fairly short design-to-market timelines for
pressure sensors and inkjet printheads; these earliest commercial devices leveraged
recent material and process developments in the integrated circuits (IC) indus-
try, primarily with the addition of wet etch technology to create through-holes
and membranes. Many ensuing MEMS developments track technological advances
in the IC industry and the development of micromachining (MEMS) specific
processes accelerated innovation and commercialization of improved versions of
existing MEMS transducers and development of new MEMS products (e.g., Fig. 1.2
for piezoresistive MEMS). For example, advances in polysilicon, metals, and
surface micromachining also enabled rapid advances for accelerometers, digital
micromirrors for digital light projectors, gas chromatographs, and film bulk acous-
tic resonators. Subsequent advances in dry etching created opportunities for smaller
devices, denser packing on a wafer, and the large aspect ratios needed for channels
or multiaxis devices. Silicon-on-insulator (SOI) wafer processes enabled thinner
membranes of high-quality single crystal silicon (SCS) and epitaxy and other thick
film growth processes enabled wafer scale packaging of high-vacuum components
such as SiTime’s resonators. Note also that the more recent product development
cycles for gyroscopes and film bulk acoustic resonators were shorter than many pre-
vious products as these products leveraged existing materials and processes with
targeted innovations in material and design performance. Follow-on products must
reach market quickly if they are to compete with existing products and build or
maintain market share with new designs.
This chapter begins with an overview of the design process and then moves into
recommended MEMS design methodologies. Case studies are used to illustrate the
methods. Material and process selection approaches are then described. Additional
methods such as modeling, design optimization, uncertainty analysis, and failure
modes and effects analysis are also introduced. Finally, the timing for utilizing
design methods is discussed. Although it is not possible to cover all aspects of
design methods for MEMS in this chapter, the following sections provide a good
introduction to a set of useful tools for MEMS development as well as references
for finding more in-depth information.