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Journal of Micro/Nanolithography, MEMS, and MOEMS

Amorphous TiAl films for micromirror arrays with stable analog deflection integrated on complementary metal oxide semiconductors
Author(s): Jan-Uwe Schmidt; Martin Friedrichs; Andreas Gehner
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Paper Abstract

Large micromechanical mirror arrays (MMA) with analog pixel deflection integrated onto active CMOS address circuitry require both high-quality planar reflective optical surfaces and a stable deflection versus voltage characteristic. However, for implementing a CMOS-compatible surface-micromachining process, certain obstacles such as a restricted thermal budget and a limited selection of suitable materials must be overcome. Amorphous TiAl is presented as a new actuator material for monolithical MEMS integration onto CMOS circuitry. TiAl films may be sputter deposited at room temperature, have an x-ray amorphous structure, and a low stress gradient. The glassy structure and high melting point make TiAl less vulnerable to stress relaxation, which makes TiAl an ideal spring material. One-level actuators with TiAl or Al-TiAl-Al structural layers and two-level actuators with separate TiAl spring and Al-alloy mirror layers were fabricated and tested with respect to their drift stability. The stability of TiAl-based actuators was found to be superior in comparison to one-level Al-alloy actuators. Two-level actuators with TiAl hinges emerge as the most promising design.

Paper Details

Date Published: 1 April 2008
PDF: 8 pages
J. Micro/Nanolith. 7(2) 021012 doi: 10.1117/1.2945230
Published in: Journal of Micro/Nanolithography, MEMS, and MOEMS Volume 7, Issue 2
Show Author Affiliations
Jan-Uwe Schmidt, Fraunhofer-Institut für Photonische Mikrosysteme (Germany)
Martin Friedrichs, Fraunhofer-Institut für Photonische Mikrosysteme (Germany)
Andreas Gehner, Fraunhofer-Institut für Photonische Mikrosysteme (Germany)

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