Spectral purity filter for multi-layer mirror, lithographic apparatus including such multi-layer mirror, method for enlarging the ratio of desired radiation and undesired radiation, and device manufacturing method

Abstract

A lithographic apparatus comprising a support configured to support a patterning device; a substrate table configured to hold a substrate; a projection system configured to project a pattern imparted to a radiation beam by the patterning device onto a target portion of the substrate; and a first multi-layer mirror and a second multi-layer mirror, the first multi-layer mirror and the second multi-layer minor being arranged along a path of the radiation beam, the first multi-layer minor and the second multi-layer mirror each having a reflectivity of at least about 50% in extreme ultra violet wavelength range, and the first multi-layer mirror configured to reduce radiation having wavelengths in a first wavelength range and the second multi-layer minor configured to reduce radiation having wavelengths in a second wavelength range different from the first wavelength range, wherein the first wavelength range and the second wavelength range are outside extreme ultra violet wavelength range.

Dependencies are inferred from the claim text.