Patent ID: 7522263

Claim:
A lithographic apparatus comprising: an illumination system configured to condition an extreme ultraviolet radiation beam; a support configured to support a patterning device, the patterning device being 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 assembly constructed to create a vacuum environment, the vacuum chamber assembly including a first vacuum chamber in which the support is located, and a second vacuum chamber in communication with the first chamber, the first and second vacuum chambers being configured to allow the introduction and removal of the patterning device to and from the first vacuum chamber via the second vacuum chamber; and a detection unit arranged within the second vacuum chamber to detect contamination on the patterning device, wherein the first and second vacuum chambers are configured to allow contamination detection on the patterning device in the second vacuum chamber when exposure using another patterning device occurs in the first vacuum chamber.