| 摘要 |
A lithographic apparatus and method in which an illumination system supplies a projection beam of radiation, a patterning system imparts to the beam a pattern in its cross section, and a projection system projects the patterned beam onto a target portion of a substrate supported on a substrate table. The projection system comprises an array of lenses located at a spacing from the substrate such that each lens in the array focuses a respective part of the patterned beam onto the substrate. A displacement system causes relative displacement between the lens array and the substrate. A particle detector is positioned to detect particles on the substrate which are approaching the lens array as a result of relative displacement between the lens array and the substrate. A free working distance control system is arranged to increase the spacing between the lens array and the substrate in response to detection of a particle by the detector such that the lens array is moved away from the substrate as relative displacement causes the detected particle to pass the lens array. Thus damage to the lens array as a result of for example scratching by particles carried on the substrate surface can be avoided.
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