LITHOGRAPHIC APPARATUS AND DEVICE MANUFACTURING METHOD

摘要

An atmospheric lithographic apparatus comprising: a substrate stage (WT) for supporting a substrate (W) in an environment with an ambient gas; a projection system configured for subsequently projecting a patterned beam of radiation onto a plurality of target portions of the substrate on the substrate stage during an exposure phase; a sensing system (20, 40) for sensing a property of the substrate on the substrate stage during a sensing phase; a reference system; and a positioning system configured for determining a position of the substrate stage relative to the reference system via a path of radiation between the substrate stage and the reference system; wherein: the atmospheric lithographic apparatus is configured for controlling the substrate stage to undergo movement relative to the reference system in the sensing phase and to undergo other movement relative to the reference system during the exposure phase; at least the substrate stage or the reference system has an outlet system (3) for providing a gas curtain of a barrier gas operative to reduce ingress of the ambient gas into a volume traversed by the path of radiation between the substrate stage and the reference system; and the lithographic apparatus is operative such that a characteristic of the gas curtain is different in at least part of the sensing phase compared to in the exposure phase.