Abstract
This paper presents a large displacement static- electricity curled-hinge comb micro-mirror with low process variability effect. Many fabrication techniques have been developed to produce mirrors in large displacement, which were influenced by the variation in CMOS MEMS process. We not only present a large electrically actuated out-of-plane displacement, but also additial a micro-spring on the side of the finger. It can decrease the influence of the variation in CMOS MEMS process. The developed procedure is a standard TSMC 0.35um 2p4m process. The metal-1 spring has only thin layers of interconnect aluminum and dielectrics. The mirror was made by metal1~4. This micro-structure has advantage of these two anchor options. The comb drives curls up after it is released. One comb drives pull the mirror up, and another comb drives pull the mirror down. The two sets of each comb drive double the Y-axis torque and zero the net Z-axis force. The comb drives rotate the mirror clockwise, and rotate the mirror counterclockwise. In the experimental stage, we have formulated a mirror for 500um x 500um and made by metal1~4. The micro-spring were used metal 1 and poly1 and its size was 4um x 21um. The nature frequency is 727Hz and the maximum displacement of this micromirror is 32um with 25V dc. The variation among each batch of production was reduced from 30% to 10%. The major contribution to the efficiency is due to the size of the micro-spring.