Mems Technology To The Development Of Polyimide Humidity Sensor

This paper reports a novel humidity sensor fabricated with MEMS technology and the standard CMOS process. Humidity sensors are widely used in many measurement and control application, including process control, meteorology, agriculture and medical equipment.Making use of MEMS technology, the humidity sensor has a metal-Al2O3– PI-metal capacitive structure by etching silicon, burying bottom-electrodes, Al2O3, polyimide in silicon trough and diffusing phosphorus to take bottom-electrodes on the surface of silicon.We have used multivibrator circuit, switch-capacity circuit and charge delta-sigma modulator to measure the sensitive capacity of humidity sensor, have simulated the result and layout using Spice software, and have analyzed the humidity sensor structure on Matlab to gain the curve of sensitive capacity.We have measured the sensitivity, hysteresis. The humidity sensor was measured to show a fairly linear dependence on the relative humidity in the range of 10%~70%, the linearity of sensitive capacity is 1.9%, and the sensitivity is 0.965pf/%RH in the range of 10%~90%RH. The maximum hysteresis is 6%RH at 80%RH.Consequently, the novel humidity sensor using MEMS technology provides the high reliability, the better hysteresis, sensitivity and linearity at 10%RH~70%RH.