Capacitor construction for use in pressure transducers

Claim 1

A capacitor construction for use in pressure transducers, comprising: a supporting substrate plate consisting of a silicon wafer and a glass wafer attached onto said silicon wafer by an electrostatic bonding method, said glass wafer being essentially thinner than the silicon wafer; a first fixed capacitor plate overlying the substrate plate; a silicon plate overlying the substrate plate to encircle the fixed capacitor plate, said silicon plate having a center part thinned to perform as a diaphragm acting as the moving capacitor plate so that well-shaped cavities are formed above and under the diaphragm structure for introduction of the measured pressure medium; a top plate overlying the silicon plate, said top plate consisting of a silicon wafer and of a glass wafer attached onto said silicon wafer and placed against the silicon plate, said glass wafer being essentially thinner than the silicon wafer; and a second capacitor plate overlying the supporting substrate plate between the first capacitor plate and the silicon plate which encircles the first capacitor plate in such a manner so as to essentially enclose the first capactor plate; whereby the second capacitor plate together with the center part of the silicon plate forms a compensating capacitor, whose capacitance (Ct) is essentially less dependent on displacement of the center part of the silicon plate than the capacitance (Cp) formed by the first capacitor plate and the center part of the silicon plate.