31 October 2016 Application of Q-type aspheric surface in the design of Wynne-Dyson projection lens
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ITRC dedicates in high precision optics for more than 40 years and focuses in lithography optics for projection system recently. The first project of the lithography optics in ITRC is an i-line Wynne-Dyson projection lens for 3D-ICs applications. The Wynne-Dyson projection lens is a classical design for unity magnification projection system. We take the advantages of the established benefits of Wynne-Dyson lens and modify it. ITRC‘s Wynne-Dyson lens is a 0.16 NA system with unity magnification, which is designed in double telecentricity and long working distance. The projection lens comprises three lenses and one concave mirror. Two aspheric surfaces are deployed in lens 1 and concave mirror. A lens with aspheric surfaces can correct for aberration and deliver a higher performance with fewer lens elements; therefore it has advantages of compact and light. However, aspheres are more difficult to fabricate and higher cost than spherical surface. In order to control the testability and manufacturability of the aspheric surface, the Q-type aspheric surfaces are applied in our design phase and manufacture process. We optimize for both performance and manufacturability by Q-type aspheric surfaces. Not only a testable and manufacturable asphere can be approached but also an additional benefits of less sensitive and cost-effective to manufacture to the required specification. In this paper, the Q-type aspheric surfaces and slope constraint are applied to a Wynne-Dyson projection lens, the testability of Q-type aspheric surfaces by the departure from best-fit-sphere and fringe density of interferometry are estimated. Furthermore, subaperture stitching interferometer system (ASI, from QED technologies) is also applied for testability comparison. The tolerance and sensitivity are also discussed. Finally, the results show a diffraction limit approached lens with testable aspheric surface is designed using Q-type aspheric surface. One of the asphere is 150 m departure from best-fit-sphere in 205 mm clear aperture, that can be tested by subaperture stitching interferometer system (ASI). The alignment tolerance of lens in decenter and tilt can be controlled in the range of ±30 micron and 20 arc-second, respectively.
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Cheng-Fang Ho, Wei-Jei Peng, Wei-Yao Hsu, "Application of Q-type aspheric surface in the design of Wynne-Dyson projection lens", Proc. SPIE 10021, Optical Design and Testing VII, 100210J (31 October 2016); doi: 10.1117/12.2245713; https://doi.org/10.1117/12.2245713


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