SPECTRAL PURITY FILTER, LITHOGRAPHIC APPARATUS INCLUDING SUCH A SPECTRAL PURITY FILTER AND DEVICE MANUFACTURING METHOD

摘要

A spectral purity filter includes an aperture. The spectral purity filter is configured to enhance the spectral purity of a radiation beam by being configured to absorb radiation of a first wavelength and allow at least a portion of radiation of a second wavelength to transmit through the aperture. The first wavelength is larger than the second wavelength. The spectral purity filter may be used to improve the spectral purity of an Extreme Ultra-Violet (EUV) radiation beam.