Integrated micro humidity sensor and micro carbon monoxide with cobalt oxide

• Main Authors: Yen-Chi Chen, 陳彥崎
• Other Authors: 戴慶良
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/75141347459591007881

碩士 === 國立中興大學 === 機械工程學系所 === 98 === The study presents a micro humidity sensor and a micro carbon monoxide (CO) sensor integrated with readout circuit on chip, which that is manufactured by the commercial 0.35 um complementary metal oxide semiconductor (CMOS) process and a post-process. The humidity sensor is composed of an oscillator circuit, a sensing comb and a humidity sensing film. CoOOH prepared by the precipitation-oxidation method is adopted as the humidity sensing film. The electrodes consist of interdigital structures, and the cobalt oxide is coated on the interdigital electrodes. The humidity sensor, which is a capacitance type sensor, changes in dielectric constant when the sensing film adsorbs vapor. The oscillator circuit is employed to convert the capacitance of the humidity sensor into the frequency output. The experimental results show that the capacitance increases from 43.08 to 196.42 pF as the humidity changes from 25 %RH to 85 %RH at 25 ℃. The resonant frequency of the humidity sensor with oscillator circuit varies from 41.13 MHz to 26.78 MHz as humidity changes from 25 %RH to 85 %RH at 25 ℃. The micro carbon CO sensor is composed of an operation amplifier, a sensing polysilicon resistor and a CO gas sensing film. The nanotube-CoOOH prepared by the hydrothermal method is adopted as the CO gas sensing film. The gas sensor, which is a resistive type sensor, changes the resistance when the sensing film adsorbs CO gas. The readout circuit is utilized to convert the resistance of the gas sensor into the voltage output. The experimental results show that the resistive increases from 19.988 kΩ to 21.08 kΩ as the CO concentration changes from 0 to 200 ppm at 25 ℃. The sensitivity of the CO sensor is about 0.188 mV/ppm and the response/recovery time was 23/35s, respectively.