Fingerprint sensing device with heterogeneous coating structure comprising a dielectric material

Abstract

The invention relates to a fingerprint sensing device comprising a sensing chip comprising an array of capacitive sensing elements. The sensing device comprises a coating material arranged in a layer on top of the array of sensing elements and comprising a plurality of cavities filled with a dielectric material. The dielectric material comprises reduced graphene oxide. Locations of the cavities correspond to locations of the sensing elements such that a cross-section area of a cavity covers at least a portion of an area of a corresponding sensing element. A dielectric constant of the dielectric material is higher than a dielectric constant of the coating material. The invention also relates to a sensing device where the dielectric coating layer containing reduced graphene oxide comprises trenches corresponding to areas between the sensing pixels filled with a fill material, where the dielectric coating layer has a higher dielectric constant than the fill material.