Patent ID: 7518382

Claim:
A sensor chip for measuring structures in a finger surface, the sensor chip comprising an array of sensor elements and a silicon chip comprising electronic circuitry, including a number of interrogation electrodes for capacitance measurements, said sensor chip further comprising: a first electrically conductive layer including said sensor elements defining positions of sensors in the sensor chip, said sensor elements being coupled to the interrogation electrodes in the silicon chip; a first dielectric layer substantially covering the first electrically conductive layer; a second electrically conductive layer on the first dielectric layer, the second conductive layer including openings formed therein over the sensor elements, said second electrically conductive layer constituting an earth plane; a second dielectric layer formed on the second electrically conductive layer; and an outer electrically conductive layer mounted on the second dielectric layer for electric coupling with structures in the finger and not covering the area over the sensor elements, wherein the silicon chip is adapted to measure the capacitance between the outer electrically conductive layer and the interrogation electrodes.