Study On The Key Technology Of Low G Pendulous Capacitive Accelerometer

It will be more higher demand for the thermal drift and measurement precision of accelerometer in the field of aerospace, navigation and guidance. Silicon-Glass bonding and ICP etching craft has been using in the processing of MEMS products. However, as the thermal expansion coefficient between silicon structure and glass substrate is mismatched, when the temperature varies, it will bring huge thermal stress which can lead to output temperature drift of accelerometer. Therefore, the article puts forward a pendulous capacitive accelerometer with stress isolation structure, and research structure design, processing and packaging, detecting circuit, system testing of accelerometer, which will be important significance to reduce thermal drift and improve measuring precision of accelerometer. The main tasks of this article are as follows:(1) Surveying the research status of accelerometer in the global, describing the principle and analyzing the weakness and strengths of various types of accelerometer, and determine the main content of the article.(2) Researching the principle of pendulous capacitive accelerometer, putting forward a pendulous capacitive accelerometer with stress isolation structure and completing the structure design. The simulation results show that under the same condition, the thermal stress of the accelerometer without stress isolation structure is about 100 Mpa and mainly concentrates at the end of torsion beam. While the stress of the accelerometer with stress isolation structure mainly concentrates at the folded-beam, and the stress in torsion beam is about 1.7MPa, which amounts to only 1.7% of the former.(3) The process fluid of accelerometer has been designed, the process of Silicon-Glass bonding and ICP etch has been adopted, and accelerometer chip has been fabricated. Simulating and analyzing thermal stress distribution of accelerometer under the condition of different plastic patch. The results show that Yang's modulus and coefficient of thermal expansion should be lower and Poisson plastic patch be larger when accelerometer is proceeding chip technology. Then building testing platform, measuring output variance of accelerometer with changing temperature under the condition of different plastic patch, and proving the correctness of simulation results.(4) The peripheral detecting circuit of accelerometer has been designed which is based on capacitive detecting method with single ended carrier modulation, dual charge amplification. Designing and simulating six modules, which are Carrier generator, differential amplifier, band pass filter, phase shift, low-pass filtering and demodulation.(5) Building experimental platform of accelerometer system. The testing results show that output waveforms of different module is same with simulation results. The sensitivity of accelerometer is 2.479V/g, the nonlinearity is 0.74%, the bias is 0.854 V, the drift is 0.4mg during 1 hour, and the precision is 0.86‰.