Design, Analysis And Preparation Of Test Device For Fatigue Analysis Of MEMS Based On The Bulk Micromachining

Recently, the reliability of MEMS attracts more and more interests as it is gradually entering as components into medical equipments, automobiles and aircraft systems. As one of the main failure modes of MEMS devices, fatigue has generally become one of the hot areas of MEMS reliability. Silicon is the most common structural material of MEMS, whose fatigue properties will directly affect the reliability of MEMS. However, there is no established mechanism to explain the fatigue behavior of silicon. Currently, test is the main method of research on fatigue failure of MEMS, and there is no decice can be used to study on the fatigue failure of silicon micro-structure which is fabricated by bulk micromachining. In view of this situation, a novel parallel-plate actuated on-chip resonant device for fatigue test of MEMS is designed in this dissertation, and it will provide a good testing means for the research on fatigue failure of silicon micro-structure. The main contents are as follows:1. The structure details and the working principle of the device are introduced firstly. Then the stiffness of the trapezoidal beam is presented by analyzing the mechanical characteristic of the key structure, and the vibration characteristics including natural frequencies and resonance shapes are obtained by the modal analysis. Finally the dimensions of the structure are worked out according to the structure design theory and fabrication conditions.2. The pull-in voltage of the device is presented after the theoretical analysis and the electromechanical coupling finite element analysis of pull-in effect based on the static analysis. Then in order to obtain damping force, the analysis of squeeze-film damping is carried on. Accordingly, the harmonic response is simulated for gaining the resonant amplitude of the device. Finally, it is indicated that the device can meet the requirements of fatigue test by the stress analysis.3. Sixty four test devices are obtained after designing the fabrication processes of silicon structure and glass substrate. Then, the measurement and the error analysis of physical dimensions are carried on, and the present errors of the device can be accepted.4. The substandard products are eliminated by the circuit testing and the capacitance testing, and seven qualified devices as well as their first two natural frequencies are obtained after the modal testing.All in all, a novel parallel-plate actuated on-chip resonant device for fatigue test of MEMS is designed, which will provide a good testing means for the study of fatigue failure of silicon micro-structure. The research results are meaningful for applying the reliability design and the quality control of MEMS.