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									                                 MICRONANO TECHNOLOGY
                                 MEMS, or microelectromechanical systems,
                                 is the integration of mechanical elements,
                                 sensors, actuators, and electronics on a
                                 common silicon substrate through
                                 microfabrication technology.

     How to Employ
     Wafer-level Packaging in MEMS IR Devices

           new paradigm in infrared light             IMT had exceeded the capabilities and
           sources is available today as a            results attained at the other foundries.
           result of the collaboration                    In one of the first real world applica-
           between Innovative Micro Tech-             tions of photonic crystals, the companies
     nology (IMT) and Ion Optics, Inc (IOI).          have now partnered to bring the PCE
     The device combines the benefits of              SensorChip MEMS device into produc-
     photonic crystal technology with low             tion. The device is a silicon micro-
     cost, high volume silicon microma-               machined infrared emitter, comprised of
     chining. The technology utilizes state           a photonic crystal modified micro-hot-
     of the art wafer-level vacuum packag-            plate that emits thermally-stimulated
     ing (WLP) from IMT, enabling low                 infrared radiation in a narrow band. The
     power battery-operated infrared emit-            wavelength of light emitted is specified
     ters built directly on a silicon chip. The       by the structure of the photonic crystal,     WLP die with high-vacuum wafer-level
     new Ion Optics’ photonic crystal                 allowing the device to be tuned to a spe-     packaging. This device already meets
     enhanced (PCE) MEMS micro-hotplate               cific waveband of interest.                   mission critical applications.
     device promises a number of significant              The key enabling technology in the        hermetic environments, including
     applications in both military combat             Ion Optics SensorChip device is the           ultra-dry air and specialty gases for
     identification and commercial and bio-           development of a photonic crystal con-        other applications.”
     medical gas sensing technology.                  sisting of an array of roughly 500,000            The first application of the Ion
         IOI faced a significant challenge in         micron-scale holes etched into a metal-       Optics photonic crystal technology is in
     that two foundries it had turned to had          coated dielectric substrate. IMT’s sophis-    supporting infrared combat identifica-
     not been able to provide the precision           ticated sub-micron photolithography           tion, specifically in avoiding “friendly
     lithography, etching, and packaging              capabilities enable very tight control of     fire” casualties. The result of the IMT/
     necessary for its photonic crystals.             the photonic crystal hole size, resulting     Ion Optics solution is a simple, low-cost
     After nearly a year of trying to achieve         in tolerances of better than 100 nm. Due      band-specific infrared emitter, which
     the required results, the company                to the tight control of the size and spac-    can provide a readily recognizable IFF
     came to Innovative Micro Technology              ing of the photonic crystal holes, the        (Identify Friend or Foe) signal in exist-
     (IMT), a leading MEMS (MicroElecto-              SensorChip MEMS device demonstrates           ing military thermal sights. This effec-
     Mechanical Systems) contract manu-               superior infrared emitter properties. For     tive combat identification, in addition
     facturer/foundry. Within the first run,          efficiency improvement, the PCE emit-         to protecting against friendly fire,
                                                      ter technology is vacuum packaged.            enables emergency pick-up, trail mark-
                                                      IMT recommended a wafer-level pack-           ing, landing beacons, and marking of
                                                      aging (WLP) approach to improve per-          high-value asset equipment.
                                                      formance and to reduce overall cost.              The same configuration is also being
                                                      Previously, the parts had been packaged       applied to produce gas sensors for med-
                                                      serially by vacuum capping individual         ical and commercial applications.
                                                      devices after the wafer was complete, a       Because of its significant cost advantages,
                                                      slow and expensive process.                   along with its reduced size and power
                                                          “IMT’s WLP is a key technology for        consumption, initial applications include
                                                      Ion Optics, as well as several of our         carbon dioxide and combustible gas sens-
                                                      other customers,” says Monteith               ing in the medical device, HVAC and
                                                      Heaton of IMT. “For Ion Optics, WLP is        safety markets.
     Unpackaged die in traditional package,           used to generate and maintain the hard
     500,000 etched holes, each with two              vacuum required for operation of the             WEB RESOURCES FOR M ICRONANO TECHNOLOGY:
     micron diameter +/- 0.1 micron toler-            photonic crystal. The technology can           ½
     ance for IR signaling.                           also be used to maintain various other

34    R&DMagazine            July 2006                                                                                      

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