Abstract: A lithographic apparatus is disclosed. The apparatus includes an illumination system configured to condition an extreme ultraviolet radiation beam, a patterning device configured to impart the extreme ultraviolet radiation beam with a pattern in its cross-section to form a patterned extreme ultraviolet radiation beam, a substrate table constructed to hold a substrate, a projection system provided with reflective optics configured to project the patterned extreme ultraviolet radiation beam onto a target portion of the substrate, a vacuum chamber constructed to create a vacuum environment, and a detection unit arranged within the vacuum chamber to detect contamination on the patterning device.

Abstract: The invention is directed to enabling substrate identification by comparing the measured distance between two features on an unidentified substrate with one or more stored distances. The one or more stored distances are the distances intended during the design of one or more substrates. The unidentified substrate is identified by a stored distance that corresponds to the measured distance. The two features are selected from a plurality of features that may be placed on a back side or a front side of a substrate. An optical system is provided for reading the features from the back side or a front side of the substrate.