30 July 2002 Performance enhancement of 157-nm Newtonian catadioptric objectives
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Newtonian design forms have been developed to explore higher numerical aperture imaging systems at a wavelength of 157 nm with elements made of CaF2 crystal. First-generation systems working at 0.60 NA are currently printing features smaller than 130 nm for resist-process-development. Second-generation design forms, working with variable numerical apertures above 0.75 NA, will push feature sizes significantly below 100 nm. Several aspects of second-generation designs have been improved to accommodate the need for characterizing and enhancing imaging performance. Closed-loop methods of optimization to reduce aberrations have been developed to characterize and control the effects of crystal-related birefringence on imagery. In addition these systems are learning vehicles to enhance knowledge of aberration-image performance dependence at high numerical apertures.
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James E. Webb, James E. Webb, Timothy Rich, Timothy Rich, Anthony R. Phillips, Anthony R. Phillips, James D. Cornell, James D. Cornell, } "Performance enhancement of 157-nm Newtonian catadioptric objectives", Proc. SPIE 4691, Optical Microlithography XV, (30 July 2002); doi: 10.1117/12.474611; https://doi.org/10.1117/12.474611

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