Fabrication and Characterization of MOSFET Pressure Sensor

• Main Author: 吳季璋
• Other Authors: 張忠誠
• Format: Others
• Language: en_US
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/32891632217515284551

碩士 === 國立海洋大學 === 電機工程學系 === 88 === The conventional pressure sensor consists of four resistors in the form of a Wheatstone bridge. A number of strain-sensitive resistors are made by diffused impurities or ion implanted impurities into silicon wafers. The resistance is fixed after the diffusion or ion implantation process is finished. It is suggested that a new Wheatstone bridge element, which consists of four Metal-Oxide-semiconductor field-effect (MOSFET) to replace traditional resistance. The advantage of MOSFET channel resistance is that it utilizes voltage to regulate the resistance. It means that we can change the channel resistance by adjusting the gate voltage so as to make the pressure sensor resistance adjustable. By virtue of this, we are able to control the sensitivity of the sensor and make zero-pressure offset voltage close to zero, not needing additional adjustment resistance to obtain the same result. In this thesis, a pressure sensor is fabricated on p(100) silicon substrate. We can obtain a thin silicon membrane using 25% KOH solution at 80℃ to etch silicon substrate. The membrane thickness is 15μm, and membrane area is 1.7mm×1.7mm. The channel resistance of MOSFET can be changed from 10KΩ to 3KΩ with adjusting gate voltage from 2V to 20V. The pressure sensitivity is obtained 2.37 mV/V‧Kg/cm2 and the nonliearity of less than 3.21% of the full scale is obtained. The temperature coefficient of offset voltage is approximately 3.25 %/℃at the temperature range between 20℃and 80℃. The temperature coefficient of sensitivity is approximately —0.54 %/℃at the temperature range between 20℃and 80℃.