| Micromechanical accelerometer sensors are typical components developed with equipments and MEMS technologies. They have extensive prospects in the fields of military industry products. Many of applications such as inertial navigation, electronic instruments require measurements along more than one axis. So such a precision integrated multi-axis accelerometer sensor is highly desired in the future. The micromechanical comb-capacitive accelerometers fabricated by bulk silicon micromachining process are widely used for having simple process, good stability and easily controllable damping coefficient.In the thesis, a novel bulk micromechanical dual-axis accelerometer is presented. The differential capacitance detecting part uses comb electrode structure which can change areas for its simple structure, good dynamic response, no touch testing, high sensitivity, resolution and linearity. This sensor can be integrated on single chip and can precisely measure acceleration in the plane. The work focuses on the design, simulation, fabrication and test.The simulation including structure-level, process-level and system-level is presented in the thesis by software ANSYS, L-edit, Intellisuite and MATLAB. By the results of static analysis, the inertial mass is 1.174mg, and the mechanical sensitivity of X and Y directions both are 32.6nm/g.Modal analysis result shows that the first two modes are the two sensitive modes, and resonant frequencies are 2774Hz, 2775Hz respectively. In system analysis, due to the accelerometer structure uses a common mass and the two axes which use the active plate together, the output of the structure is a mixed signal of the two axes. So in system simulation uses interface circuit based on divided frequency can effectively separate the mixed signal of two active axes. The fabricated accelerometer structure is 5260μm×5260μm in size. Through testing, electrical sensitivity is 30.34mV/g, resonant frequency is 2.4kHz, and the system bandwidth can achieve 1.2 kHz. |
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