Successful fabrication of polymer based low voltage electrostatic actuators

Abstract

In this work we present the successful fabrication of a polymer based zipper actuator to achieve a high stroke electrostatic actuation. The whole process is completely wafer level compatible and allows the integration of optical elements, e.g. mirrors or microlenses, without further assembly steps. Instead of the commonly used silicon [1] we use the UV-curable OrmoComp to build the actuator. OrmoComp has a significantly lower elastic modulus (about 1 GPa), only a fraction of actuation voltage is necessary for a similar deflection. The major drawbacks of the polymer based approach are a challenging fabrication process, which is described in this paper, and, due to the stiffness, a low resonance frequency. All process steps are realized as a lithographic structuring of positive tone, respectively negative one resists, allowing the full wafer level fabrication of polymer based electrostatic actuators. A specific development process makes it possible to induce stress in the OrmoComp layer, creating an out of plane actuator based on common two dimensional lithography process steps. We present the results on the first completely wafer level fabricated zipper actuator, creating an out-of-plane motion up to 470 µm at an actuation voltage of 374 V