Capacitive long-range position sensor for microactuators

Design, fabrication and measurements for a capacitive long-range position sensor for microactuators are presented. The sensor consists of two periodic geometries (period/spl ap/8-16 /spl mu/m) on resp. a slider and a sense-structure with minimal gap-distance of /spl sim/1 /spl mu/m. A relative displacement between the two results in a periodic change in capacitance. In open-loop operation the change in capacitance vs. slider displacement is measured using synchronous detection. Adjusting the minimal gap-distance with additional sense-actuators increases the capacitance. In closed-loop operation the position of the sense-structure is controlled to keep the sensor-capacitance at a larger constant value. Our results indicate that the position precision is increased to 18 nm in closed-loop operation compared to 70 nm in open-loop operation.