Research Of New Z-axis Differential Capacitive Acceleration Sensor

Micro mechanical acceleration sensor overcomes many disadvantages of thetraditional mechanical sensor, and it has been widely used in many fields, which,capacitive acceleration sensor was well received because of its high sensitivity, lowtemperature drift characteristics. According to the phenomenon of the design ofcapacitive acceleration sensor in Z axis prone to interference and analysis is notaccurate enough, this paper carried out a detailed analysis of the Z-axis differentialcapacitive accelerometer.Firstly, this paper introduces the basic concept, feature, technical backgroundand the present domestic and foreign research situation of MEMS. This paperanalyze the inaccuracy of the theoretical model of the traditional capacitiveaccelerometer, then chose a fully differential capacitance structure; analyze thestructure characteristics of capacitive acceleration sensor, and then choose thecomb structure as the plate detection capacitance. Build a more accurate model tosolve slightly reverse because of the non-sensitive direction acceleration.Secondly, according to the selected comb structure, analyzes the stress effect.This paper discusses the influence and the size of Casimir for MEMS accelerationsensor, to determine the comb specifications; analysis the capacitance of capacitorsunder the effect of static electricity and the approximate amount of edge effectinfluence on the capacitance value, to determine the comb specifications. Theanalysis of these two kinds of force determines the comb size to eliminate theinfluence of Casimir and the edge effect.Then, a brief introduce of the process on the basis of the integrated circuit andthe common process technology of MEMS, including the surface processing, bulksilicon technology, LIGA, CMOS-MEMS technology, and to prepare for work onthe follow-up sample preparationFinally,.the analysis confirms the Z axis fully differential capacitanceaccelerometer with the staggered vertical combs. Respectively analyzing thetorsional characteristics of the every direction of acceleration effect, the theoreticalmodel of the change in Z axial capacitance can be obtained and solved., theaccelerometer within the range of design to achieve the best detection results by optimized design of the structure. The design and simulation are also verified byusing the FEM tool ANSYS, the simulation results show that the sensitivity of theaccelerometers is0.37fF/g, the resonance frequency is4615Hz, can be goodoperate in most working conditions.