Patent ID: 8730448

Claim:
A lithographic apparatus comprising: a substrate table constructed to hold a substrate; a duct having a wall defining an opening with a sloped inner surface of the wall, the duct configured to provide a flow of a cooled gas to the opening, the duct comprising an annular slit formed in the sloped inner surface and having an annular perimeter in a plane transversely crossing the duct; and an annular chamber connected to the annular slit and including an entrance constructed and arranged to receive a pipe for supplying gas to the annular chamber, wherein the annular slit has a slit width along a direction substantially perpendicular to the plane transversely crossing the duct that varies along the perimeter of the annular slit, the slit-width variation being arranged to provide a substantially uniform gas flow field inside the opening; a projection system configured to project a patterned radiation beam through the opening and onto a target portion of the substrate; and a cooling apparatus controlled by a control system, the cooling apparatus configured to cool the gas such that gas that travels from the opening to the substrate has a predetermined temperature when the gas is incident upon the substrate.