Capacitive long-range position sensor for microactuators

Design, fabrication and measurements for a capacitive long-range position sensor for microactuators are pre-sented. The sensor consists of two periodic geometries (period = 8-16pm) on resp. a slider and a sense-structure with minimal gap-distance of- 1 pm. A relative displace-ment between the two results in a periodic change in ca-pacitance. In open-loop operation the change in capaci-tance vs. slider displacement is measured using synchro-nous 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 con-stant value. Our results indicate that the position preci-sion is increased to 18 nm in closed-loop operation com-pared to 70 nm in open-loop operation