Research Of Meso-piezoresistance Effect Micromechanical Gyroscope Based On GaAs Substrate

Gyroscope is the core device in inertial navigation and guidance, which determines the precision strike capability of weapons. The high sensitivity gyroscope is an embargo technology to foreign, so it is the needs of developing the gyroscope technology in national defense. With the advantages of small size, low cost, greater overload performance, the gyroscope becomes the research hotspot around the world. A novelty meso-piezoresistance effect gyroscope with the higher piezoresistive coefficient than silicon is proposed in the paper. And the main research works will focus on the aspects of sensitive mechanism, structure design, fabrication process, performance measurement of this gyroscope.The operating principle of meso-piezoresistance effect is:if a mechanical signal is acted in a related mechanical nano-structure, the corresponding strain distribution will be produced in the structure. The strain distribution can generate built-in electric fields, and then change the electronic energy state which will influence on the value of the tunneling current. In short, a weak mechanical signal can be converted into a strong tunneling current signal.The gyroscope studied in this paper using the electromagnetic driven approach which with the advantages of controllable driven force and stable amplitude. The driven modal and detection modal is designed as slide film damping, squeeze film damping, respectively. As the movement gap between the proof mass and the base plate is 15μm, the quality factors of driven modal and detection modal are 4591,167, respectively. The natural frequencies of driven and detection modal are 3530Hz and 3671Hz according to simulation analysis. The performance bandwidth of micromechanical gyroscope is 76Hz; the anti-impact ability in driven X direction and detection Z direction are 24579g,7974g, respectively. The displacement sensitivity of the structural is 5.21×10-8 m/°/s, the stress sensitivity is 2.52×10-2Mpa/°/s, the measurement range is±288°/s, and the thermal noise is 0.3665°/h/(?). The coupling process between the nano-film pressure-sensitive structure and micromechanical gyroscope structure is studied. It is achieved the combination of MEMS manufacturing process and multi-layer nano film fabrication process by using some key MEMS processes technology, including the air bridge, ohmic contact, control holes, self-stop etch. And micromechanical gyroscope with the meso-piezoresistance effect is fabricated successfully.The key technology of magnetic driven circuit and weak signal detection circuit of meso-piezoresistance effect micromechanical gyroscope are also researched. The open-loop driven circuit, driven feedback detection circuit, meso-piezoresistance bridge detection circuit, adjustable regulated power supply circuit, demodulation circuit, filter circuit are designed, which achieve the driven and weak signal detection of micromechanical gyroscope.The performance of MEMS gyroscope is tested by the building measurement system. In the atmospheric pressure, the resonant frequency of driven modal is 4060Hz; and the quality factor of micromechanical gyroscope is 815. The sensitivity of micromechanical gyroscope in negative resistance area and positive resistance area is 19.8mV/°/s and 52.8μV/°/s by theoretical calculation. According to the experimental results, it is show that the detection sensitivity is 9.35μV/°/s as the gyroscope working in positive resistance area not the desired negative resistance area. The linearity coefficient is 0.99 when the angular velocity in the range of [-500°/s,+500°/s].The analysis and testing results show that the gyroscope works in the positive resistance area due to the drift of bias voltage, therefore the sensitivity is low, but the angular velocity detection is achieved in principle. The electromagnetic driven-meso-piezoresistance effect detection approaches, manufacturing process method and experimental measurement method is verified feasible, which provide theoretical foundation and experimental foundation for further study of meso-piezoresistance effect micromechanical gyroscope.