A Highly Sensitive Pirani Gauge with Dual Sensing Materials

• Main Authors: CHUANG,CHING-SHENG, 莊景勝
• Other Authors: CHEN,CHUNG-NAN
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/k379ph

碩士 === 國立高雄應用科技大學 === 光電與通訊工程研究所 === 105 === A novel and highly sensitive CMOS-MEMS Pirani gauge with dual sensing materials is presented in this paper. In order to extremely improve the sensitivity of Pirani gauges, this study integrated the structure of a Wheatstone bridge and dual sensing materials with positive and negative temperature coefficient of resistance into a Pirani sensor. Instead of the traditional Pirani sensor with a single sensing resistor, the novel Pirani gauge is composed of quadruple sensing resistor. In quadruple-sensing-resistor structure, all of the sensing resistors are simultaneously heated to achieve a higher operation temperature to enhance the output voltage at the same bias voltage. The temperature of the sensing resistors were heated up and changed with pressure due to the heat loss variation of gas conduction around the sensing device, and it results in the resistance of sensing resistors increase and decrease simultaneously. Therefore, the sensitivity of the novel Pirani gauge will be higher than those of traditional Pirani gauges. The Pirani gauge with aluminum and polysilicon sensing resistors was successfully manufactured by adopting CMOS process and bulk micromachining technology in this work. The temperature coefficients of resistance of aluminum and polysilicon were measured as 0.253 %/℃and -0.387 %/℃(at 300 K), respectively. The signal of pressure response of single-sensing-resistor structure and quadruple-sensing-resistor structure are 0.016 V and 0.197 V under 0.67 V bias voltage of the bridge circuit, respectively. The temperature of those device were estimated as 75 ℃ and 205 ℃. According to the measurement results, the sensitivity of Pirani gauge can be extremely improved up to 12 times compared with single-sensing-resistor structure by adopting the design of dual sensing materials and quadruple sensing resistors.