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23 January 2006 High-fill factor micro-mirror array for multi object spectroscopy
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Programmable multi-slit masks are required for next generation Multi-Object Spectrograph (MOS) for space as well as for ground-based instruments. A promising solution is the use of MOEMS devices such as micromirror arrays (MMA) or micro-shutter arrays (MSA), which both allow the remote control of the multi-slit configuration in real time. In the present work we developed and microfabricated a novel micro mirror array suited for this application. The requirements are: high contrast, optically flat (λ/20) mirrors in operation, high fill factor, uniform tilt angle over the whole array and low actuation voltage. In order to fulfill these requirements we use a combination of bulk and surface micromachining in silicon. The mirrors are actuated electrostatically by a separate electrode chip. The mirrors are defined by deep reactive ion etching in the 10μm thick device layer of a silicon-on-insulator (SOI) wafer, whereas the suspension of the mirrors is defined by a patterned poly-silicon layer hidden on the backside of the mirrors. The mirror size is 100 x 200 μm2 and the dimensions of a typical cantilever suspension are 100 x 5 x 0.6 μm3. On a separate SOI wafer the electrodes and the spacers are processed by using a self aligned delayed mask process. The first results on the mirror chips show that the micromirrors can easily achieve the desired mechanical tilt angle of more than 20° associated with a good surface quality, which is necessary for a high contrast spectroscopy.
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Severin Waldis, Pierre-Andre Clerc, Frederic Zamkotsian, Michael Zickar, Wilfried Noell, and Nico de Rooij "High-fill factor micro-mirror array for multi object spectroscopy", Proc. SPIE 6114, MOEMS Display, Imaging, and Miniaturized Microsystems IV, 611408 (23 January 2006);

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