Patent ID: 10031428

Abstract:
A system is disclosed for reducing overlay errors by controlling gas flow around a patterning device of a lithographic apparatus. The lithographic apparatus includes an illumination system configured to condition a radiation beam. The lithographic apparatus further includes a movable stage comprising a support structure that may be configured to support a patterning device. The patterning device may be configured to impart the radiation beam with a pattern in its cross-section to form a patterned radiation beam. In addition, the lithographic apparatus comprises a plate (410) positioned between the movable stage (401) and the projection system (208). The plate includes an opening (411) that comprises a first sidewall (411a) and a second sidewall (411b). The plate may be configured to provide a gas flow pattern (424) in a region between the movable stage and the projection system that is substantially perpendicular to an optical axis of the illumination system.