Investigation of hysteresis phenomenon of Si-based piezo-resistive pressure sensor

• Main Authors: Hsin-Nan Chiang, 蔣信男
• Other Authors: Kuo-Ning Chiang
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/80096391031865764431

碩士 === 國立清華大學 === 動力機械工程學系 === 94 === At present, the silicon piezoresistive pressure sensor is a mature technology in industry and the requirement for measurement accuracy is more rigorous in many advanced applications. In order to meet the needs of industrial mechanical signal sensing, a variety of characteristic of pressure sensor need to be taken into account. Micro piezoresistive pressure sensor is fabricated by MEMS process with the formation of a thin piezoresistor on silicon substrate by using the ion implant technique. The main operation principle is that the external pressure loading causes the deflection, strain and stress occurred on the silicon membrane. Then, a piezoresistive effect occurs as a result of a resistance change in the piezoresistor on silicon membrane. By using the Wheatstone bridge to transform the mechanical signal to an output voltage, the unknown pressure loading was measured. However, the sensitivity of piezoresistive pressure sensor is relatively high. The ambient temperature, humidity, and a background noise pressure may disturb its performance. Therefore, drifts of output voltage in the isothermal condition may result in a residual stress on the aluminum trace due to thermal cycle loading. This is called the thermal hysteresis phenomenon and the variation of the output voltage is called thermal hysteresis voltage. Among other critical issues, this hysteresis phenomenon should be closely examined for ultimate better sensor accuracy. For this reason, this research was designed to investigate the effect of external loading on the output voltage of pressure sensors. The observed influence of hysteresis voltage will be compared between the experiments and simulations. Moreover, another main goal in this research is to analyze the relation dependence of the thermal hysteresis voltage on trace layout. The residual stress on the trace under a temperature loading was estimated, and the pseudo temperature was utilized to match the residual stress. Furthermore, based on the process of pressure sensor, this research adopts the concept of pseudo temperature combined with a finite element analysis to obtain the thermal hysteresis voltage. After several numerical analysis of thermal hysteresis voltage, the experiments would performed to validate the simulation results. At the same time, the variation of thermal hysteresis voltage under different trace layout after the simulated validation was observed. In addition to the thermal hysteresis phenomenon, this research would investigate the stress hysteresis phenomenon of pressure sensor by means of the experiments. Different from the thermal hysteresis , the stress hysteresis phenomenon is always induced by the external pressure loading. In summary, the hysteresis phenomenon of pressure sensor was systematically discussed by both the simulations and experiments walk, and the results could provide as a design guideline for designers in the relative fields.