Patent ID: 8259287
Filing Date: 2012-09-04
Classification: G03F

Abstract:
1. A lithographic apparatus, comprising: a substrate table constructed to hold a substrate; a projection system configured to project a patterned radiation beam onto a target portion of the substrate, the projection system including an optical element; a liquid supply system configured to supply liquid to a space between the projection system and the substrate table, such that the liquid is in contact with the optical element and at a level that meets or exceeds a bottom surface of the optical element; a level-detection device configured to determine the level of the liquid; and a control system configured to dynamically vary a rate of extraction of liquid by the liquid supply system from the space, dynamically vary a rate of supply of liquid by the liquid supply system, or both, during exposure based on the determined level of liquid, such that the determined level of liquid is maintained between a certain minimum and a certain maximum.