Reflective systems design study for soft x‐ray projection lithography

We have investigated several all‐reflective designs which have potential application for soft x‐ray projection lithography. The resolution goal for all designs was 0.1 μm or better. Different design aspects including usable field size, distortion, obscuration, number of mirrors, surface shape (spherical versus aspheric), and system packaging were explored. Trade‐off studies were made between three types of systems: strip field scanning systems, and large field nonscanning systems with both curved and flat mask. Several candidate unobscured designs with 0.1 μm resolution are presented.