Reflective optical designs for soft x-ray projection lithography

摘要

All-reflective, unobscured optical designs were developed to help identify a candidate first- generation system to be used in soft x-ray projection lithography. The resolution goal for all designs was 0.1 $mu@m, or better, at a design wavelength of 13 nm. Different design aspects including usable field size, image distortion, number of mirrors, telecentricity, surface shape (spherical versus aspheric), and system packaging were explored. Trade-off studied between systems requiring scanning and full-format nonscanning systems were made. The tolerance sensitivity analysis for a representative design demonstrated that as-built performance will be driven by the mirror surface irregularity tolerance; the required tolerance levels are briefly discussed.