Optical apparatus and lithographic apparatus using the optical apparatus

Abstract

An optical apparatus and a lithographic apparatus including the optical apparatus. The optical apparatus includes a substrate having an aperture for passing light; a transmissive optical element covering the aperture of the substrate; and an optical contact bond between the substrate and transmissive optical element, the optical contact bond being spaced from the aperture a sufficient distance such that stress forces in the transmissive optical element from the optical contact bond to the aperture are below an acceptable stress threshold. The optical contact bond geometry herein, for example, minimizes a contact area and provides a quasi-kinematic (near-exactly constrained) interface between the substrate and the optical element.