. . . . . . . . . . '

MEMS: Another Fast- moving Target for the Compounds to Track

by Jo Ann McDonald, US Correspondent

MEMS are the manipulative little devices that have wormed their way to the top of the list of interesting "new" technologies this fall. When looking into the increasing number of MEMS

initiatives, one conjectures that their popularity is because MEMS offer systems designers the opportunity to marry the "smaller, faster, smarter" philosophy with old fashioned facts

of mechanical and human life.

w here si l icon leads, the compounds inevitably fol- low. Siliconers are hot on

the MEMS trail these days, and as soon as systems designers start de- manding more of their MEMS devices (more light, faster speed, radiation hardness, higher temperatures, etc...), wc may see viable niches for MEMS based on II1-Vs and the wide bandgap materials.

When announcing DARPA's recent $50 million MEMS initiative, Dr. Kaig- ham (Ken)J . Gabriel defined Micro- electromechanical Systems (MEMS) as: "an enabling t echno logy that merges advances in information pro- cessing, storage, and display with advances in sensors and actuators to bring about a rew)lution in the way we both perceive and control the environment."

Formerly the program manager for DARPA's MEMS effort, Ken has re- cently assumed the directorship of DARPA's Electronic Technology Of- rice, replacing Lance Glasser who entered the commercial sector. The two names are familiar ones to the US c o m p o u n d s e m i c o n d u c t o r R&D community. Ken went on to note that, "MEMS is a natural progression in the capabilities of semiconductor devices. The ability of MEMS to gather and process information, de- cide on a course of action, and

Motorola's SENSEON T M Carbon Monoxide Chemical Gas Sensor.

control the environment through actuators increases the affordability, functionality, and number of smart systems. The enhanced capability of smart systems enabled by MEMS will increasingly be the product differen- tiator of the 21st century, pacing the level of both defense and commercial competitiveness."

MEMS are getting smarter. Sandia Laboratories in Albuquerque is set- ting a fast pace and calling the MEMS they design and fabricate, "intelligent multipurpose micromachines." Ac-

cording to Sandia's science writer, Neal Singer, "a smart micromachine is better than a dumb one, just as a car with a gas indicator, speed- ometer, and cruise control is easier on a driver than one that merely runs. An intelligent micromachine can sig- nal for more power, communicate that it is operating too fast or too slow, or even perform actions on an automated basis." According to Paul McWhorter, manager of the effort at Sandia's Microelectronics Develop- ment Laboratory (MDL), "This will

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m o m i c sca le in ~ , c l c c u ~ nicr~ a n d m a l e r i a l s s c i e n c e s . N o m ~ t e r h o w smart, ~r w h m y o u call d~em, MI~-S l ~ e s e m a n e w o p p m ~ - ni ty t o c l evcHy c o m b i n e t h e advan- t a g ~ o f m i n i a t u r i T z t i o n a n d t h e

Integrated Accelerometers (50,000 g Rating). 5andia'$ integrated and 3-level poly surface micromachines.

integration of multiple componen t s into one system, using the manufac- turing process steps learned f rom microelect ronic fabrication.

Market forecasts Current est imates are that today's MEMS market is around the $2 billion sales mark, and predominant ly sensor based. By the year 2000, more than 50% of MEMS will be actuator based. By that time, the total worldwide MEMS marke t will rise to around $14 billion, but it will take until 1999 to realize that rampup. An SPC MEMS marke t study that DARPA has cited forecasts that marke t segments by the year 2000 will break out to: 25% pressure sensors, 21% optical switching, 20% inertial sensors, 19% fluid regulation and control, and 6% mass data storage, leaving 9% for various smaller niches.

Dust mite = 300 microns. Human hair = 75 microns long. Small driving gear = 50 microns wide. Large gear = 1600 microns wide (These photos courtesy of Steve Montague of Sandia National Labs). Contact: Paul McWhorter, Manager of Integrated Micromechanics, Microsensors and CMOS Technology Dept. tel: [1] 505 844-4683.

Pa0e 31 IVogNo5

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Motorola def ines state of the art commerc ia l env i ronmenta l sensors based on M E M S carbon monoxide device Ideally typical of commercial efforts that are fielding state of the art MEMS now is Motorola's launch of their "Senseon" chemical sensor family, touting how silicon micromachining offers " u n c o m p r o m i s i n g pe r fo r - mance for air quality and environ- mental monitoring." The product will be officially introduced at Sensors Expo, 22 October 1996, in Philadel- phia, Pennsylvania, see photos.

The SENSEON MGSIO00 series of chemical gas sensors is based on thin film MOS technology, manufactured under license of Microsens SA in Switzerland. The series features an embedded heater layer to raise the temperature of the metal oxide film in order to be more sensitive to the

Nested drive gears in 3-level technology (generates more torque).Courtesy of Sandia National Labs.

3-level poly-powered, surface micro-machined mirror for optical interconnects. (Courtesy of Sandia National Labs.)

Page 54 , ! , ~ S Vo19No5

Motorola SENSEON in close up.

Micromachined mirror w/drive motors for optical interconnects (Rack and pinion drive). Courtesy of Sandia National Labs.

target gas, combined with a micro- machined silicon diaphragm for re- duced power consumption. Designed to support the most current stan- dards for residential CO detectors, the device is fitted with a stainless steel mesh and an active charcoal filter for protec t ion against damaging elements, and to selectively screen

out noise gases. The sensors are priced at under $10 each in low quantities. Complete research, devel- opment , and manufacturing of Mo- torola's chemical sensors is being implemented in Motorola's existing facility in Toulouse, France. Future products from the MGS1000 series will include the 1200 methane sensor

DARPA's newest $ 5 0 million MEM$ initiative As of July, proposals are in and are now under consideration at DAR- PA for their newest $50 million MEMS initiative (Issue: PSA 1565, SOL BAA 96-19). Quoting from the BAA: "The long-term goal of DAR- PA's MEMS program is to merge computa t ion , sensors, actuators, and mechanical s tructures to radi- caUy change the way people and machines interact with the physi- cal world. As military information systems increasingly leave com- mand centers and appear in weap- ons and in the pockets and palms of combatants, they are getting closer to the physical world, creat- ing new opportuni t ies for perceiv- ing and controlling the battlefield environment.

"This phase of the DARPA MEMS program will build advances in MEMS devices, device integration, and fabrication resources to devel- op and demonst ra te new system concep t s and result ing capabil- ities." DARPA seeks proposals in three broad technology areas:

i. MEMS systems developments and demonstrat ions, particularly but not exclusively in signal pro- cessing, con t ro l of distr ibuted, m u l t i - e l e m e n t (10,000 senso r ) and actuator systems, and electro- magnetic beam steering;

ii. MEMS manufacturing resource development , including but not limited to: MEMS electronic design aids, MEMS fabricat ion/processing e q u i p m e n t , g e n e r a l i z e d MEMS packaging techniques and tools, and visualization/analysis tools for MEMS device and systems;

iii. Integrated microfluidic sys- tems for molecular processing and detection.

R e c e n t a c c o m p l i s h m e n t s o f DARPA's MEMS program to date include the demonstra t ion of an acce lerometer operating at near 80,000 g's, optical diffraction grat- ings tha t e l e c t r o m e c h a n i c a l l y switch light in 40 nanoseconds and a fabrication service that has already provided hundreds of dis- t r ibuted users from diverse back- grounds with affordable access to micromachining processes at reg- ular, scheduled intervals.

For the latest information via the web: ht tp: / /e to .sysplan.com/ETO/ MEMS/index.html

vo, .o Page 55 .~.~.~ ii!.~!~ii!:~i ~

and a control chip that features signal condit ioning, ou tpu t drivers, and interfaces, both planned for introduc- tion in 1997.

Their t echnology road map in- cludes such sensor refinements as sensitivity to new target bases and lower power devices.

Motorola's MEMS activities will also be featured in Philadelphia at an all day MEMS seminar on 23 October, chaired and organized by Roger Grace, President of Roger Grace Associates in San Francisco. The agenda includes global market over- views, university and research lab activities, and MEMS applications. For more information, Roger Grace can be contacted at tel: 415/821-

6881 fax: 415/641-6156 email: rgra- ce 1 @ aol.com

MEMS headliners at big U.S. shows: SEMICON/Southwest (Austin, Texas, 14-17 October) and IEDM (San Fran- cisco, California, 8-11 December ) SPIE's 1996 Symposium on "Micro- machining and Microfabrication, '" held in conjunction with SEMICON/ Southwest '96 will feature three days of MEMS related meetings, covering the ent i re spec t rum of activities, worldwide.

P lenary p r e s e n t a t i o n s include: "MEMS in 3D" by Kristrofer Pister of

UCLA, "CAD & CAE for MEMS: Emergence from the Dark Ages" by Selden Crary of the University of Michigan, "Commercializing MEMS- Too Slow or Too Fast?" by Stcven Walsh of the New Jersey Institute of Technology, and "Application of Mi- cro-Machining Technology to Optical Devices and Systems" by Hiroyuki Fujita of the University of Tokyo. Detailed information is available from SPIE o v e r t h e w e b : h t t p : / / www.spie.org/ or by tel: 360/676- 3290, fax: 360 /647-1445 , email: spie@spie.org

The 2000 engineers present at this year's IEDM in San Francisco will hear about MEMS as one of the three plenary presentations. Kicking off

Challenges in packaging MEMS How MEMS are packaged is critical, especially for space applications. Many of the potential applications for MEMS devices will likely be in "hostile" environments, for which they seem well-suited. MEMS are already in use in high temperature e lect ronic (HTE) applications. As stated above, the chapter by James Lyke on "Packaging Technologies for Space-Based Microsystems and Their Elements" is a comprehensive overview of the entire field of study, and should be on everyone's "must read" list. At Phillips Lab, James Lyke and his colleagues have sponsored approximately 27 SBIR programs in the area of relevant advanced packa- ging, resulting in the development of over three dozen MCM designs. Phillips works largely with compa- nies that are doing leading edge work, although, according to Lyke, "there are many shades of grey in packaging." For example, "what was normally called the chip and wire hybrid technology, which we use as a commodity item in a design if it is required, in many cases is a case of pushing the advancement of that technology to a further degree."

Where are the current sights and focus in packaging? "The areas of packaging that we ' re most inter- ested in today involve cost reduc- t i o n in 2D p a c k a g i n g , 3D h e t e r o g e n e o u s packag ing , and there's a new frontier, and not a lot of work being done, in the advance- ment of the next generation of 2D

packaging," Lyke continues. '~I~ere are questions that involve the very foundation of designing ICs for more optimal performance, that involve the design and d ev e lo p m en t of complementary packaging technol- ogies which we call Ultra High Density Interconnect. In our spare time, Capt. Ken Merkel and I are trying to develop papers directed to

this new, exci t ing area." Lyke's chapter in the Aerospace Corpora- tion report, cited above, builds on the heritage of the last decade of research and packaging, and it con- tains the philosophies and taxo- nomies from which to build future MEMS systems that will clearly change packaging technologies as we know them today.

Page 56 i i i ~ l Vo19No5

Catching MUMPS at MCNC This sort of "MUMPs" is quite d i f ferent than the w e l l - k n o w n childhood ailment. MUMPs is one of the MEMS processes referred to above, and is the acronym for M u l t i - U s e r MEMS P r o c e s s e s . MUMPs w a s put. in place under the funding and direction of DAR- PA at the MEMS Technology Ap- p l i c a t i o n s C e n t e r a t t h e Microelectronics Center of North Carolina (MCNC in Research Tri- angle Park, North Carolina). The director of the program is Karen Markus. Another good contact is David Koester , M em ber of the Technical Staff.

Contact is via email at: mem- s@mcnc.org. The MUMPs program is designed to provide low-cost MEMS process technology to the industry, academic, and govern- men t research and deve lopment communi t ies in the US and Cana- da. The front end suppor t activities and access to the technologies are provided by MCNC's Electronic T e c h n o l o g i e s Division. Partici- pants may purchase a 1 cm x 1 cm die site for a nominal fee (about $180 US) with approxi- mately 15 unreleased dice deliv- e red . Layout s e rv i ce and die release are available for an addi- tional fee.

MUMPS is a three layer polysili- con surface micromachining pro- cess designed to be as general as possible to provide the user with the grea tes t p rocess flexibility. Polysilicon is used as the structural material, deposi ted oxide (PSG) as the sacrificial material, and silicon nitride for electrical isolation from the substrate.

The p rocess is der ived f rom work per formed by the Berkeley Sensors and Actuators Center at the Universi ty of California at Berkeley. Devices fabricated using the MUMPs process include linear c o m b drives, ro tary side drive motors, wobble motors, and resis- tive fuse links. Detailed informa- tion on the Center, the process, and results are available over the MCNC w e b s i t e : h t t p : / / m e m - s .mcnc.org/mumps.html

will be Professor Kensall Wise, Direc- tor of the Cen te r for In tegra ted Sensors and Circuits at the University of Michigan in Ann Arbor who ' s address is simply "MEMS SYSTEMS" There is also slated a special invited paper titled "IC MEMS Microtransdu- cer" where researchers from ETH in Zurich, Switzerland, will review the interaction of microelectromechani- cal sys tems wi th IC technology , providing a roadmap of current tech- nological approaches, a description of new microtransducer prototypes, a summary of recent progress in CAD tools, and a critical evaluation of MEMS product potential sen photo. (Paper #20.1, H Baltes et al., ETH). Other MEMS-related papers will also bc heard at IEDM. For registration and o ther information, IEDM now has a websi te as well: h t tp : / /h i s .com/ *iedm or contact Melissa Widerkehr, IEDM Conference manager, at tel: [1] 301/527-0900, fax: [ 1 ] 301/527-0900.

Aerospace corp reports authorized for public release The dramat ic progress in r ecen t years is due to the combined efforts o f hard w o r k i n g sc ient i s t s in a number of sectors. For example, the U.S. space c o m m u n i t y has b e e n working in the MEMS area for some time. The Aerospace Corporat ion, which functions as an "architect- engineer" for national security pro- grams in the USA, gathered together a seminal r epo r t in 1993 (t i t led "Micro- and Nanotechnology Appli- cations for Space Systems) that char- a c t e r i z e d this rapidly advanc ing technology. In late 1995, that repor t was updated and now serves as one of the guiding documents for MEMS development in the USA. Titled "Mi- croengineering Technology for Space Systems," the present repor t recog- nizes that the term "nanotechnology" has evolved to represent the more basic research level of trying to grow nano materials, of which wide band- gap semiconductors play an impor- tant role.

According to the study's lead edi- tor, Henry Helvajian of The Aero- space Corporat ion, the discipline now encompasses "the design, mate- rials synthesis, micromachining, as- sembly, integration, and packaging of miniature 2-D and 3-D sensors, a c -

tuators, microelectronics, and MEMS for the development of intelligent microinstruments." The current re- port is a crash course on the field and an excellent read. Especially note- wor thy is the t rea tment of the small n a n o s a t e l l i t e ' c o n c e p t , b a s e d on MEMS t e c h n o l o g y , t h a t t o t a l l y changes our current approach to utilizing space.

T h e c h a p t e r o n p a c k a g i n g , authored by James c. Lyke of the U.S. Air Force's Phillips Laboratory at Kirtland AFB in New Mexico, is an especially comprehens ive packaging pr imer on earth-bound systems as well as for spacecraft. Recently, the U.S. government authorized the re- lease of the pair of studies to the public, free of charge. They can be obtained through

Henry Helvajian, The Aerospace Corporation~ P.O. Box 92957-M/S M5-753, or by faxing a r eques t through 310/336-7680 or via email: henry_helvajian (w qmail2.aero.org

MEMS clearninghouse An especially helpful DARPA-backed service is the "MEMS Clearinghouse," which maintains a comprehens ive online website. A scan of the "ar- chives/newstuff" port ion dates back to postings beginning in August of 1994 and is perhaps the quickest and most painless way of getting up to speed on international developments within the MEMS community. De- spite (or perhaps due to) the inform- ality of the format, the amount of information and ease of access is impressive. The site also includes listings of the various MEMS fabrica- tion centers and company informa- t ion on each (Lucas NovaSensor C o m p a n y , F r a u n h o f e r G e - s e l l s c h a f t . . . t h e l ist is g r o w i n g quickly). The virtual clearinghouse also includes a listing of companies that are hiring MEMS developers and posts a wide variety of academic opportuni t ies and staff openings in the U.S., as well as at many different international sectors and institutions. The URL for the clearinghouse is: h t t p : / / m e m s . i s i . e d u / m e m s . Those without web access can contact the clearinghouse tW email, directed to: info-mems@isi.edu, or by postal mail to: USC/Information Sciences Insti- tute, 4676 Admiralty Way, Marina del Rey, CA 90292, USA.