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° at voltages between 200 and 320 V. At pull-in, a digital tilt angle of approx. ±21° 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 × 1.2 mm with a bending of less than 0.2 μm 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.