Fabrication and Measurement of Thermal Type Altimeters

• Main Authors: LI, MENG-JHE, 李孟哲
• Other Authors: CHEN, CHUNG-NAN
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/c9y77y

碩士 === 國立高雄應用科技大學 === 光電與通訊工程研究所 === 105 === This study designs and manufactures the first thermal type barometer altimeter to replace current piezoresistive and capacitive altimeters. The thermal type barometer altimeters have the advantage of smaller size and simpler process compared with commercial piezoresistive and capacitive altimeters. The material with temperature coefficient of resistance formed on a thermally isolated suspended structure was used as a sensing resistor of the thermal altimeter. The temperature of the sensing resistor was heated up and changed with altitude due to the variation through gas heat loss around the sensing device, and it results in the change of the resistor’s resistance. Eventually, the variation of resistance can be readout by a Wheatstone bridge circuit. In this dissertation, thermal type barometer altimeter with a microbridge structure and a narrow gap were fabricated by adopting CMOS process and bulk micromachining. The bulk micromachining can prevent the sensor membrane from sticking onto the substrate. A aluminum thin film was used as a sensing resistor of the thermal altimeter. The temperature coefficient of resistance of the sensing resistor and the pressure response of the device were measured in this work. And then the sensitivity of the sensor can be calculated. For the measurement of altitude response, the thermal type barometer altimeter was connected to a Wheatstone bridge circuit and an amplification circuit to measure altitude reponse. In this study, the thermal type barometer altimeter was manufactured successfully. The equivalent depth of gap and the resistance of altimeter are 1.4 μm and 67 Ω, respectively. According to the measurement results of pressure response, the sensitivity of the theoretical altitude response was estimated as 0.4 μV/m under bias voltage of 1.054 V and a heating temperature was 170 °C. The output voltage difference of the altimeter was amplified 200 times and measured as 0.077 V between the altitude change of the second floor and sixth floor at same operating condition. Base on the result of height response, the thermal type barometer altimeter has the potential for development.