6 May 2005 Design and fabrication of tilting and piston micromirrors for maskless lithography
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In this paper we present the design and fabrication results of tilting and piston micromirrors for their potential applications in DUV and EUV maskless lithography. The dynamic characteristics such as stability, damping, and the settling time of various types of electro-mechanically coupled micromirrors are investigated using the perturbation method, linear control theory, and numerical simulation. Non-dimensional control parameters are identified and transient optimization is carried out to minimize the systems’ settling time. It is found that vertical double-comb tilting micromirrors and clamped double-flexure piston micromirrors have superior stability. The mirror hinge is proposed to function as a built-in resistor to introduce optimal electrical damping for EUV micromirrors operating in vacuum. We have developed a low-temperature (<420°C) IC compatible SiGe process, in which SiGe can be doped at different levels without annealing to function as a structural (conductive) and damping (resistive) material. Self-aligned processes using "spacer nanolithography" to define ultra-thin nano-scale actuation gaps for low-voltage operation have been developed to fabricate both tilting and piston micromirrors. We have successfully constructed double-comb tilting micromirrors with 300-nm fingers and 40-nm finger gaps, and double-flexure piston micromirrors with 80-nm thick flexures and 80-nm actuation gaps. The mirror sizes are in the range of 10 to 0.5 mm.
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Yijian Chen, Yijian Chen, Chi Hui Chu, Chi Hui Chu, Yashesh Shroff, Yashesh Shroff, Jen-Shiang Wang, Jen-Shiang Wang, William G. Oldham, William G. Oldham, } "Design and fabrication of tilting and piston micromirrors for maskless lithography", Proc. SPIE 5751, Emerging Lithographic Technologies IX, (6 May 2005); doi: 10.1117/12.599389; https://doi.org/10.1117/12.599389

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