Capacitive humidity sensor in CMOS technology

An integrated relative humidity sensor that combines a capacitive sensor with CMOS measurement circuitry on the same silicon chip has been designed, fabricated and tested. The device provides square wave. Its frequency varies with humidity over the entire range from 0% to 100%. The sensor element, which is an integrated part of the circuit, is an interdigital lateral capacitance structure formed by the aluminium layers of the CMOS process.