Improvement of Reliability of SOI Electrostatic Tilt Mirror by Using Landing Island Structure

Abstract

We have improved the performance and reliability of an SOI electrostatic MEMS tilt mirror by using a landing island structure in the substrate layer. The landing island is electrically isolated from the substrate layer and has the same electrical potential with the suspended mirror structure. It works as a mechanical stopper to suppress the hysteresis due to the electrostatic pull-in and to avoid the electrical short-circuit between the actuator electrodes. The air-squeezed dumping effect of the landing island has also been found to eliminate the ringing and improve the step response. This structure can be made by the conventional SOI bulk micromachining with two photo masks. We used the new newly developed tilt mirror in a variable optical attenuator and cleared the Bellcore GR1221.