A novel capacitive-type humidity sensor using CMOS fabrication technology

This paper reports a novel capacitive humidity sensor integrated on a polysilicon heater. The sensor was fabricated with the industrial standard CMOS process to achieve a cost-effective solution for accurate and reliability. The sensing material polyimide was obtained by a post-processing step after the standard CMOS fabrication. The sensing principle of the sensor is based on the dielectric constant change of deposited polyimide due to absorption/desorption of vapor. The passivation (silicon nitride) layer with no limitations to the electrode selection is between the electrode and sensing material in order to improve the reliability of the relative humidity for the sensors. The humidity sensor was measured to show a linear dependence on the relative humidity in the range of 20-70%, the maximum hysteresis is 3%. (C) 2003 Elsevier B.V. All rights reserved.