A CMOS interdigital capacitive humidity sensor with polysilicon heaters

A CMOS interdigital capacitive humidity sensor with polysilicon heaters is presented. Polyimide was used as the sensing material. In order to find out the relationship between filling effect of deposited polyimide and the spacing distance of Al electrodes, another interdigital capacitive humidity sensor with no passivation around Al electrodes was also fabricated. The measured results show that good filling effect of deposited polyimide can be realized when the gap between interdigital electrodes is twice the thickness of deposited polyimide. By using the polysilicon heaters, the hysteresis of the humidity sensor is less than 2%RH.