Failure analysis of a multi-degree-of-freedom spatial microstage

Spatial microstages are microfabricated controlled platforms that can be popped out of the fabrication plane and are free to move in three-dimensional (3D) space. Spatial microstages have shown promise for use in MOEMS for adaptive optics, automatic focusing systems, fiber optic alignment/precision positioning, real time optical alignment, interconnects, and a host of other applications. These devices were designed and fabricated to position a controllable stage in 3D space from microassembly and microfabrication. Microstages can be designed and fabricated to move in plane (x, y) and out of plane (z). Advanced microstages are designed to move in plane, out-of-plane, rotate, and tilt about x, y, and z. Design and fabrication of the rotational and tilt components are critical in performing the three-dimensional pop up and tilting action needed for precise micropositioning. The device used for analysis contains linear racks driven by electrostatic actuators. The actuators are attached to a microstage through a hinge component with revolving, rotating, and tilting joints. The actuators allow x, y, and z positioning while the hinge allows rotational motion along the stage. Failure analysis of the Sandia fabricated microstage was performed on released and as fabricated microstages. Failure analysis of these devices revealed design and fabrication irregularities along the revolving components of the hinge. This paper will discuss the design and functionality of the microstage, failure analysis activities and failure mechanisms found in polysilicon fabricated microstages, corrective actions and design improvements.