Relay lens used in an illumination system of a lithography system

摘要

A relay lens is provided in an illumination system for use in microlithography. The relay lens can be used to uniformly illuminate a field at a reticle by telecentric light beams with variable aperture size. The relay lens can include first, second, and third lens groups. At least one of the second and third lens groups can include a single lens. This can reduce costs and increase transmission by requiring less CaF2 because fewer optical elements are used compared to prior systems.