Design of an Extended Image Field Soft-X-Ray Projection System

A soft-x-ray projection system has been designed, which consists of spherical components to be coated with multilayer reflection coatings. In the design, a two-mirror system and a spherical reflection mask, the optical aberrations were minimized. The design enables a resolution of sub-100 nm over a circular image field with a diameter of 4 mm at a wavelength of 10.5 nm. The assembly tolerances of the system and the fabrication tolerances of the substrates have been calculated. The surface roughness determined from our superpolished quartz substrates amounts to 0.3 nm, which is sufficient to meet the required specifications.