Humidity microsensor in CMOS Mitel15 technology

Microsensors fabrication based on a standard CMOS process represents a very attractive alternative for low cost high reliable transducers that include the conditioning along with the detection component. This paper report on the implementation of a relative humidity (RH) microsensor built in Mitel15 technology. The sensitivity mechanism is based on the resistance variation of a polyaniline layer spun over the conveniently built electrodes of the transducer when RH of the environment changes. Although less convenient that the capacitive RH microsensors, resistive based microsensors in the present configuration present two major benefits. They require simple one step low cost postprocessing to accomplish the sensor and the transducer as built is not affected by the swelling of the polymer due to water absorption at high RH. Besides, the conditioning circuitry is very simple and robust, and requires low power consumption. The performances of the active material and of the transducer are reported The clearly indicate that RH micromachined sensors based on resistive sensitive mechanisms are feasible in Mitel15 technology. One single low cost postprocessing performed after the completion of the process enables the fabrication of such sensors.