Capacitive transducer for accurate displacement control

Abstract

The underlying theory, design, and operation are presented for an interdigitated capacitive displacement transducer supported on an air-bearing stage. This device provides a purely electrical means of displacement measurement and offers the possibility of being closely matched to the substrate against thermal perturbations. Tests on a prototype system show the basic capacitive transducer to have a sensitivity of 2.6 mV/μm and a position uncertainty of 4 nm set by thermal noise.