In MOEMS'99, we reported a silicon torsional resonant mirror driven by a PZT plate through link beam leverage effects and confirmed the device operation. Our device isnechanically reliable and stable since there are no metal leads on the vibrating silicontorsional beams and the mirror is supported by 6 beams. This time, we presents an improved device having much higher performance through both d e s i p and process optimization based on detailed FEM simulations and refinement of the fabrication process.As is shown in Figure 1, the mirror (4 x 4 mm) is designed to vibrate around the center axis and actuated through the link beams, which are connected to the mirror edges with a small offixis distance to the center axis. The link beams are attached to the cantilever bealgwhich is located only at the one side of the mirror for size reduction, and driven by a PZT ceramic plate on the cantilever beam. To drive and monitor the mirror, electrode on the PZT was divided into two parts (PZT, for driving, PZT, for monitoring).We camed out modal and frequencyresponse simulations of the device by FEM simulator ANSYS in which PZT characteristics were included. Figure 2 is a typical first vibration mode where the state at the maximum scan angle with 90 degree phase delay to the dive signal is shown. Figure 3 shows the dependence of the scanning angle on the o€hxis distance e ( L 2 0 0 0 pm, w=20 pm, H1=50,100,190 pm), which is obtained from the frequencyresponse simulation results. Since existence of off-axis distance e is the source of the rotational torque, and fairly lager e corresponds to a smaller scanning angle, there should be asuitable distance with a given thickness of the mirror substrate. We found such optimal values as e=200pm for H1= 100pm. The results also show that thicker substrate is suitable for obtaining a lager scanning angle.The fabrication process is quite simple. Using only two ICPRIE processes (one for backside etching and the other for front etching), a silicon mirror base was fabricated. Metals (Cr/Au) were then spattered on to the designated mirror area. After these processes, the PZT ceramic was glued on the lever. TheFkaged and the magnified view of the mirror are shown in Figure 4 and 5 respective1y. Figure 6 shows an example of the device performance (L=5000pm, H1=200 pm) showing mechanically scanned angle vs. AC voltage applied to the PZT. 5 2 0 degree angle at AC 4 volts could be obtained at the resonant frequency of 480Hz with quality
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