Patent attributes
A lithographic projection apparatus includes a beam path for a beam of radiation, a projection system, a support structure for supporting a patterning device and a substrate holder for holding a substrate. The beam path includes a radiation system for providing the beam of radiation, and the projection system projects the beam of radiation patterned by the patterning device onto a target portion on the substrate. At least one chamber that includes at least part of the beam path. A purge gas supply subsystem is coupled to the chamber for supplying a flow of purge gas to the chamber, and a control unit is arranged to switch the purge gas supply subsystem between at least two different modes of operation. The control unit controls the purge gas supply subsystem to supply mutually different respective non-zero flow rates of the purge gas to the chamber in the different modes of operation.
