Coupled Electro-thermal-mechanical Analysis And Test Of Micro Gas Pressure Sensor With Micro-hotplate

As the rapid development of microelectronic and micromachining technology, micromation has become an important development direction of a sensor. As micro gas pressure sensor based on micro-hotplate (MHP) fabricated using the technology compatible with standard IC process has less volume, lower power, wider range, and more fast thermal response, etc, so it has become an important research direction in MEMS field at home and abroad. This paper mainly researched MHP-based micro pressure sensor from theory analysis, structure optimization, and performance test. The main contents as follows:Electro-thermal theoretical analysis of the sensor is conducted using classical heat transfer theory and rarefied gas dynamics, and electro-thermal theoretical analysis model is built; Thermal-mechanical analysis of the MHP with different thickness distributions of thin films is conducted using finite element analysis software CoventorWare. The simulated results show that the MHP thermal deformation direction is related with thickness distributions of thin films. Then, combining the MHP electro-thermal theoretical analysis and thermal-mechanical finite element modeling, coupled electro-thermal-mechanical theoretical analysis model of sensor is built. The theory model is solved using MATLAB, and studying the MHP thermal deformation effect on the coupled signal output of sensor at constant current condition and constant temperature condition respectively.The key problems in MHP-based micro gas pressure sensor design are introduced, three different support styles of suspended MHP are analyzed and compared using ANSYS software. The simulated results show that circular support structure MHP not only has little solid heat loss, but also can release thermal deformation induced by the expansion of thin films.Aiming at the requirement of the sensor dynamic performance test, perfect pressure automatic control algorithm of the measurement and control system, and design a fuzzy controller of online adjusting parameters to realize gas pressure automatic control. The experiment results show that the controller has characteristics of fast dynamic response and small error, and can acquire better control result over the entire pressure range. Furthermore, the MHP-based micro gas pressure sensor test research is also developed, and test the sensor response characteristic at the conditions of constant current, constant voltage and constant temperature. The test results show that for constant current and constant voltage operating mode, the sensor is apparently sensitive in the pressure range of 10～5×10~4Pa, while the sensitivity falls down at higher gas pressure due to too low working temperature, and the output voltage amplitude is only a few hundreds of millivolts from 10 Pa to 10~5Pa. For constant temperature mode, the sensor output voltage increases if elevating gas pressure, and higher sensitivity appears in the pressure range of 10～10~5Pa so that the output voltage amplitude is about a few volts. In addition, from many times test process, the sensor has good repeatability and stability.