Research On High-resolution MOEMS Accelerometers Based On Integrated Optics

Micro-accelerometers are very important sensors for anti-vibration measurement of vehicles, seismic monitoring, inertial navigation and guidance systems, especially high-resolution accelerometers withμg-resolution or ng-resolution, not only can be used in inertial navigation systems for precise positioning of the target, but also have wide applications in other scientific fields, such as ultra-precise measurement of Earth’s surface and the distribution of the gravity field of outer space. In recent years, MEMS acceleration sensor foreign technology has developed rapidly, but the domestic acceleration sensor has not yet been a technical breakthrough. Therefore, the research we made is to fill the blank in the micro-acceleration sensor, and has great significance for enhancing the overall level of inertial navigation technology.This dissertation presents a high-resolution MOEMS (Micro-Optical Electro-Mechanical System) accelerometer based on integrated micro-optics, which combines the grating interference with silicon MEMS (Micro-electro mechanical system) technology. A sandwich structure, which consists of a grating, a PZT (Piezoelectric Translator), and the micro-machined structure, is designed as the acceleration sensing chip for the first time. The main content of the dissertation is as follows.Firstly, we introduced the principle, classification, development of the micro-accelerometer, and then made a comparison with kinds of MEMS and MOEMS accelerometers. The research main contents, object and novel ideas of this work were also introduced.Combined the Michelson-Interferometer with the grating measurement technique, and based on the phase modulation-demodulation technique, the phase-sensitive grating interference theory consisting of the grating, PZT, and the mirror has been analyzed, and the functional relationship between the intensity and the displacement has also been derived. As the acceleration is the quadratic differential of the displacement, and therefore, the phase-sensitive grating interference can be extended for the acceleration measurement.Combination the grating interference theory and the MEMS technology, the theory and model of a high resolution MOEMS accelerometer based on the integrated micro-optics have been established, and the functional formula between the intensity and the acceleration has also been given. By use of ANSYS, the simulation and analysis software, the parameter design, model, performance of the mechanical structure have been simulated and analyzed. According to the characteristics of the accelerometer system output signal, the signal detection method by means of the lock-in amplifier was introduced.We also made much effort to the fabrication of the prototype of the proposed MOEMS accelerometer. Use the electron-beam lithography to fabricate the grating, and use the photolithography, ICP (Inductively Coupled Plasma) to manufacture the silicon micro-machined structure. Then, we completed the package of the sandwich structure, which consisted of the grating, PZT, and the silicon micro-machined structure, as the acceleration sensing chip. The principle and electric components of the signal processing circuit were also demonstrated.According to performance parameters of evaluation of the accelerometer, test validation experiments of the MOEMS accelerometer about sensitivity, linearity, hysteresis, etc., have been made, and experimental results show that the fabricated MOEMS accelerometer provides acceleration sensitivity of1676V/g and high-resolution acceleration less than3.1μg in the linear region, and with good stability and repeatability.Finally, we summarized the research done, and made prospects for the future work.