Lithographic apparatus, device manufacturing method, and method of applying a pattern to a substrate

摘要

A lithographic apparatus includes a patterning subsystem for transferring a pattern from a patterning device onto a substrate controlled in accordance with recorded measurements of level variations across a surface of the substrate. A level sensor is provided for projecting a level sensing beam of radiation to reflect from a location on the substrate surface and for detecting the reflected sensing beam to record the surface level at said location. The level sensor incorporates at least one moving optical element to scan the substrate surface by optical movement in at least one dimension to obtain measurements of surface level at different locations without mechanical movement between the level sensor and the substrate. Optical path length equalization measures may be employed, using shaped reflectors and/or additional moving mirrors, to avoid focus variation during the scan.

主权项

1. A lithographic apparatus comprising:
a patterning subsystem for transferring a pattern from a patterning device onto a substrate, the patterning subsystem being controlled in accordance with measurements of level variations across a surface of the substrate; a level sensor for projecting a patterned level sensing beam of radiation to reflect from a location on the substrate surface and for detecting the reflected sensing beam to record a height of the surface level at said location, wherein said level sensor incorporates at least one moving optical element and whereby said level sensor is arranged for optically scanning the substrate surface by the level sensing beam in at least one dimension to obtain measurements of the height of the surface level at different locations without corresponding mechanical movement between the level sensor and the substrate; and a focus control arrangement for maintaining focus of said patterned beam on said substrate during said level sensing beam scan as an indication of focus error; wherein said focus control arrangement is responsive to height variations measured during at least one previous sensing beam scan as a predictor of focus error in a current level sensing scan of the level sensing beam of radiation.