1 March 1993 Improved four-mirror optical system for deep-ultraviolet submicrometer lithography
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The design for a rotationally symmetric four-mirror optical system with reduction magnification 5 x for deep UV (λ = 248 nm of a KrF excimer laser) submicrometer lithography is developed. Initially by using the paraxial quantities, numerical solutions are found for the system, which is free from the four off-axial third-order aberrations-coma, astigmatism, field curvature, and distortion. Aspherization is carried out to the spherical mirror surfaces to reduce the axial and residual off-axial higher order aberrations. The numerical aperture of the final system is as large as 0.38, which gives a Rayleigh resolution of 0.4 μm and hence is useful in submicrometer lithographic applications.
Jong-Tae Kim, Jong-Tae Kim, Hong-Jin Kong, Hong-Jin Kong, Sang-Soo Lee, Sang-Soo Lee, } "Improved four-mirror optical system for deep-ultraviolet submicrometer lithography," Optical Engineering 32(3), (1 March 1993). https://doi.org/10.1117/12.61056 . Submission:

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