High-precision MEMS Accelerometer Based On Fabry-perot Cavity

MEMS optical accelerometer is utilized to measure the acceleration indirectly by converting the displacement of the sensing mass into optical signal(wavelength,frequency,energy).Due to the high-precision acceleration measurement and reliable resistance to electromagnetic interference,it has been widely used in aircraft navigation,artificial satellite attitude adjustment,national basic gravity network mapping,and petroleum seismic exploration.Moreover,high-precision MEMS optical accelerometer is of great importance in improving the properties of strategic weapons in military field.In this dissertation,a silicon-based optoelectronic MEMS accelerometer based on the Fabry-Perot(F-P)cavity is designed by using the principle of dynamic wavelength tuning.The silicon-based infrared light source,semiconductor photodetector and acceleration sensing structure are integrated to realize the miniaturization of the sensor.The sensing structure of the accelerometer consists of a flexible support beam and a central mass block.At the bottom of the sensitive mass block and the top of photoelectric detection layer,a distributed Bragg reflector is prepared by using thin film deposition technology to form an F-P optical cavity.The physical models of the accelerationsensitive units,F-P optical cavity,new folding support beam and the limited block structures in sensors are established,resulting in the overall modeling of the optoelectronic MEMS accelerometer.The relationship between mass block displacement and transmission light wavelength offset,as well as the relationship between S-type support beam deflection and system acceleration is studied.The functional model between system acceleration and transmission light wavelength is established,and its linearity is greater than 99.99%.The finite element simulation software is used to design and optimize the structural parameters.The simulation results show that the designed accelerometer has a working frequency of 510 Hz,a measurement range of ±5 g,a sensitivity of 54.8 nm/g,and a maximum resolution of 1mg.Based on the simulation results,the wafer layout of the proposed MEMS accelerometer is designed and optimized,and the main fabrication processes such as etching,film deposition,and bonding are studied.First,the anisotropic dry etching process is used to release the sensing mass,and the film deposition technique is applied for preparing the reflective mirror of the optical cavity.Then the silicon-silicon bonding process for three-dimensional integration of the infrared light source layer,the sensitive structure layer and the photodetection layer is performed.