Patent ID: 7158208

Claim:
A lithographic apparatus, comprising: an illumination system that supplies a beam of radiation; a patterning system that patterns the beam; a projection system that projects the patterned beam onto a target portion of a substrate, the projection system comprising a lens array spaced from the substrate, such that each lens in the lens array focuses a respective part of the patterned beam onto the substrate; a displacement system that causes relative displacement between the lens array and the substrate to increase a spacing between the lens array and the substrate; a particle detector that detects particles on the substrate that are approaching the lens array as a result of relative displacement between the lens array and the substrate; and a free working distance control system that increases the spacing between the lens array and the substrate in response to detection of a particle by the particle detector, such that the lens array is moved away from the substrate using the displacement system as relative displacement causes the detected particle to pass below the lens array.