Abstract: The present application relates to an apparatus and to a method for removing at least a single particulate from a substrate, especially an optical element for extreme ultraviolet (EUV) photolithography, wherein the apparatus comprises: (a) an analysis unit designed to determine at least one constituent of a material composition of the at least one single particulate; and (b) at least one gas injection system designed to provide a gas matched to the particular constituent in an environment of the at least one single particulate; (c) wherein the matched gas contributes to removing the at least one single particulate from the substrate.

Abstract: The present invention relates to a method for determining an alignment of a photomask on a sample stage which is displaceable along at least one axis that is parallel to a chuck surface of the sample stage, and is rotatable about at least one axis that is perpendicular to the chuck surface, which method comprises the following step: rotating the sample stage by a predefined angle and measuring a height change of the photomask during rotation at a predetermined, non-vanishing distance with respect to the rotation axis for the purpose of determining the alignment of the photomask on the sample stage.

Abstract: The present application relates to an apparatus and to a method for removing at least a single particulate from a substrate, especially an optical element for extreme ultraviolet (EUV) photolithography, wherein the apparatus comprises: (a) an analysis unit designed to determine at least one constituent of a material composition of the at least one single particulate; and (b) at least one gas injection system designed to provide a gas matched to the particular constituent in an environment of the at least one single particulate; (c) wherein the matched gas contributes to removing the at least one single particulate from the substrate.

Abstract: A wrap spring clutch according to some embodiments has a center shaft; a wrap spring wrapped around the center shaft in a direction of winding, and having two wrap spring ends and an abutting surface for co-operation with a friction surface; and a hollow shaft positioned around the wrap spring; and a cooling device positioned adjacent the friction surface.