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Journal of Micro/Nanolithography, MEMS, and MOEMS

Development of a focusing micromirror device with an in-plane stress relief structure in silicon-on-insulator technology
Author(s): Wolfgang Kronast; Ulrich Mescheder; Bernhard Müller; Rolf Huster
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Paper Abstract

A new design concept for a dynamically focusing silicon membrane mirror with 6-mm diameter and electrostatic actuation was realized. With this concept, membrane buckling by residual compressive stress inside the membrane can be avoided, which is observed even in crystalline membranes fabricated in silicon-on-insulator (SOI) technology and leads to severe distortion of stress-sensitive devices, such as membrane-based micromirrors. To eliminate the influence of residual stress (compressive or tensile), a membrane suspension with a new stress-relief design was developed by the use of finite element (FEM) simulations. The improvement was achieved by a special tangential-beam suspension, which allows an in-plane expansion or contraction of the membrane, which reduces the stress-induced deformation and leads to substantially flat and distortion-free micromirrors (distortion<λ/10 ). Measurements of realized devices are in very good agreement with the prediction of the FEM simulation. A comparison of membranes with the new stress-relief suspension shows, for example, for a membrane with 6-mm diameter and 10-μm thickness, a distortion of 54 nm compared to 340 nm for a conventional rigidly clamped membrane. A focus range between 97 mm and infinity (flat position) can be used in accordance with the simulation.

Paper Details

Date Published: 21 January 2014
PDF: 11 pages
J. Micro/Nanolith. MEMS MOEMS 13(1) 011112 doi: 10.1117/1.JMM.13.1.011112
Published in: Journal of Micro/Nanolithography, MEMS, and MOEMS Volume 13, Issue 1
Show Author Affiliations
Wolfgang Kronast, Hochschule Furtwangen Univ. (Germany)
Ulrich Mescheder, Hochschule Furtwangen Univ. (Germany)
Bernhard Müller, Hochschule Furtwangen Univ. (Germany)
Rolf Huster, Hochschule Furtwangen Univ. (Germany)

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