Catadioptric optical system for scatterometry

摘要

A catadioptric optical system having a high numerical aperture operates in a wide spectral range. The catadioptric system includes a correcting plate and an optical system. The correcting plate conditions electromagnetic radiation to correct at least one aberration. The optical system reflects a first portion of the conditioned electromagnetic radiation, refracts a second portion of the conditioned electromagnetic radiation, and focuses the reflected first portion of the conditioned electromagnetic radiation onto a target portion of a substrate. The first portion of the electromagnetic radiation is not refracted by an optical element, allowing the catadioptric optical system to operate in a broad spectral range.