15 October 2012 Maskless lithography alignment method based on phase-shifting Moiré fringes technique
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The relative position of wafer and mask can be calculated by information of Moiré fringe during alignment, a maskless lithography alignment method based on circular gratings Moiré fringes phase-shifting technique is proposed in this paper. Circular grating Moiré fringes have characteristics of measuring simultaneously angular displacement and line displacement. Location information of wafer in alignment can be real-time reflected in spatial phase of Moiré fringes. A digital micromirror device controlled by a computer is used to generate phase-shifting grating labels, and phase-shifting Moiré fringes will be formed by superposition of phase-shifting grating labels with grating label on the wafer. The position information of wafer can be abstained by phase analysis using Fourier transform method combined with phase-shifting technique,and gives feedback to the displacement stage to realize alignment. The theory basis of this method is emphatically introduced. Also, application of this method in maskless lithography alignment is analyzed in detail. Simulation results show that this method is high in accuracy, simple in operation and simple in algorithm. It provides a feasible method for lithography alignment technique.
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Jiangping Zhu, Jiangping Zhu, Song Hu, Song Hu, Jungshen Yu, Jungshen Yu, Yan Tang, Yan Tang, } "Maskless lithography alignment method based on phase-shifting Moiré fringes technique", Proc. SPIE 8418, 6th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Design, Manufacturing, and Testing of Smart Structures, Micro- and Nano-Optical Devices, and Systems, 84180L (15 October 2012); doi: 10.1117/12.971463; https://doi.org/10.1117/12.971463

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