Design And Test Of Capacitive Pressure Sensor Based On Single Cristal Silicon

Touch mode capacitive pressure sensor (TMCPS) has distinct advantages, such as good linearity, high sensitivity and strong overload protection, over other pressure sensor. It is widely used in many fields, such as industry, medical treatment, military application and scientific research. The study in capacitance pressure sensor, which is based on Micro-Electro-Mechanical Systems (MEMS), is comparatively insufficient in our country. Merely relying on import sensor has restricted the development of science and technology. Therefore, developing a practical MEMS sensor, which has high sensitivity and good linearity, has become an urgent problem in sensor research.To achieve the better characteristics, a new type of touch mode capacitive pressure sensor named as DTMCPS is devised, which has an additional thin notch on the bottom electrode of traditional TMCPS. Small deflection theory and finite element analysis are employed to analyze the diaphragm deformation. According to the result of the analysis, DTMCPS provides an effective way to solve the contradiction between long linear range and high sensitivity. Compared to present touch mode capacitive pressure sensors, the new sensor has long linear range with the same high sensitivity. On the other hand, the new structure hasn't complicated the fabrication process, therefore hasn't increased the cost.The structure, which is fabricated on the SOI material, and its fabrication process have been designed based on the theoretical analysis. The key process technique is silicon fusion bonding. There are only three masks have been used in the lithography, which has simplified the overall process.For testing the sensor's character, several kinds of micro-capacitance test circuits are analyzed. After that, the circuit which is based on operational amplifier is designed and fabricated. It includes a biphase rectifier and a sine wave power.Finally, we test the performance of the sensor, analyze the reasons that cause error and propose some way to improve the sensor's performance.