Post Processed Foundry MEMS Actuators for Large Deflection Optical Scanning

Abstract

In this research effort, we developed MEMS micromirrors which are suitable for large angle deflections for optical scanning applications using the PolyMUMPs™ foundry fabrication process. This foundry process uses polysilicon and gold as the structural layers to form the bimorph beam structures which make up our actuation assembly. From both modeling and experimental testing, current micromirror designs fabricated in the PolyMUMPs™ process do not meet the deflection requirements to enable large angle scanning. As a result, we developed several post processing deposition techniques, using the PolyMUMPs™ structural layers as the baseline structure, to enable the necessary upward deflections to permit large angle scanning. In this research, we design, model, post fabricate, and test high out-of-plane MEMS actuators intended for integration with SOI micromirror arrays to enable the broadband, high fill-factor scanning applications. These arrays are designed to scan in multiple directions due to the segmented actuation design. The upward deflection is accomplished through material selection and design control (i.e., structure length, material thickness, material coefficient of thermal expansion (CTE), deposition temperature, and material layer composition) of bimorph structures. Following the post processed fabrication and sacrificial release; the initial deflection profiles are measured and compared against COMSOL™ models.