Metal-Insulator-Semiconductor BaTiO3 Humidity Sensor

Humidity characteristics of BaTiO₃ sensor, which is developed in metal-insulator-semiconductor structure, have been investigated and a simple model for relation of capacitance- relative humidity has been suggested. Based on radio frequency magnetron sputtering technique and optical lithography, the humidity sensor was fabricated on silicon substrate by depositing BaTiO₃ thin film and evaporating a layer of aluminum in turn. The result shows that, under operating voltage of 3.5 volt and frequency of 1 MHz, as relative humidity ranges from 12 to 92% RH, change of capacitance is about 430% with a hystersis of 4.5%. It has been found that humidity characteristics of the sensor are dominated by chemical adsorption in lower humidity, and by physical adsorption in higher humidity. Influence on humidity characteristics by temperature has been discussed also.