Humidity sensors using porous silicon layer with mesa structure

Abstract

A capacitance-type humidity sensor in which a porous silicon layeris used as a humidity-sensing material was developed. This sensor wasfabricated monolithically to be compatible with the typical IC processtechnology except for the formation of porous silicon layer. As the sensor ismade as a mesa structure, the correct measurement of capacitance is expectedbecause it can remove the effect of the parasitic capacitance from the bottomlayer and other junctions. To do this, the sensor was fabricated using processsteps such as the localized formation of porous silicon, oxidation of theporous silicon layer, and etching of the oxidized porous silicon layer. Fromcompleted sensors, capacitance response was measured at a relative humidity of25-95% at room temperature. As a result, the measured capacitance showed anincrease over 300% at the low frequency of 120 Hz, and showed littledependence on temperature between 10 and 40 °C.