Quasi-static micromirror with enlarged deflection based on aluminum nitride thin film springs

Uniaxial electrostatically driven micromirrors with very large non-resonant rotation angles are presented. The mirrors achieve an analog deflection of about +/- 12 degrees at voltages between 200 and 320 V. At pull-in, a digital tilt angle of approx. +/- 21 degrees is found. A mirror control for a nearly linear characteristic curve, by using a counter torque is approved. The key for large quasi-static deflections are novel aluminum nitride based thin film springs. The high mechanical strength of AlN enables the fabrication of thin but stable torsion springs. The mirror has a size of 1 mm x 1.2 mm with a bending of less than 0.21 mu m and high surface quality (Ra < 2 nm). The rotational eigenfrequencies are found to be between 37 and 73 Hz and the eigenfrequencies of the vertical mirror movement are between 1235 and 1751 Hz. (C) 2014 Elsevier B.V. All rights reserved.