SPECTRAL PURITY FILTERS FOR USE IN A LITHOGRAPHIC APPARATUS

摘要

A spectral purity filter includes a plurality of apertures extending through a member. The apertures are arranged to suppress a first wavelength of radiation and to allow at least a portion of a second wavelength of radiation to be transmitted through the apertures. The second wavelength of radiation is shorter than the first wavelength of radiation. The apertures extend though the member in different directions in order to be substantially in alignment with radiation constituting a non-parallel beam of radiation.