Implementation of vertical-integrated dual mode inductive-capacitive proximity sensor

Abstract

This study extends the authors' previous concept to employ nanoporous anodic aluminum oxide (np-AAO) as insulation and dielectric layer [1] to form the vertical-integrated inductive-capacitive proximity sensor. The advantages of this vertical-integrated inductive-capacitive proximity sensor are as follows, (1) enlarge the range of sensing distance: capacitive-sensing remains sensitive for short-distance object and long-distance object remains detectable by inductive-sensing, (2) conductive and non-conductive objects can be detected, (3) chip size is reduced by the vertical-integrated design, (4) fringe-effect is enhanced by the spiral-coil, and (5) np-AAO has good electrical properties: dielectric constant 7.4 (oxide:3.9), electrical resistivity: over hundred MΩ,-cm (similar to oxide). Preliminary fabrication results demonstrate the vertically integrated inductive-capacitive proximity sensor, and the tests show its sensing-range can reach 0.5~5mm.