An XYZ Gap-Closing Microstage Actuator Based on a Two Mask SOI Process

In this work, the design, fabrication process and theoretical characterization of an XYZ gap-closing microstage actuator based on a simple, two-mask silicon-on-insulator (SOI) process is presented. An aluminum thin film is selectively deposited on the serpentine supporting springs of the actuator forming a bimorph structure. The lattice mismatch between silicon and the aluminum film introduces a tensile stress on the metal film, which upon the structure being released, contracts and causes the bimorph supporting spring to bend out of plane, enabling the Z downward motion of the stage. By applying adequate potential differences between the substrate and the structure, as well as between the gap-closing drive actuators and the structure, the structure can be manipulated in a threedimensional fashion.