Patent ID: 8059261

Claim:
A lithographic apparatus, comprising: an illumination system configured to condition a beam of radiation, said illumination system defining a focal plane through which the beam of radiation passes; a support structure configured to support a patterning device at a location, said patterning device serving to pattern the beam of radiation according to a desired pattern; a masking device configured to obscure at least a part of the patterning device from the beam, the masking device comprising a first masking structure arranged to obscure said part in a first direction relative to said location and a second masking structure arranged to obscure said part in a second, different direction relative to said location, wherein said first and second masking structures are disposed in the vicinity of the focal plane in a mechanically uncoupled arrangement relative to each other to substantially prevent transfer of vibration from one of the first and second masking structures to the other; a substrate holder configured to hold a substrate; and a projection system configured to project the patterned beam onto a target portion of the substrate, wherein during projection of the patterned beam onto the target portion of the substrate, said second masking structure is moved by a motor while said first masking structure is stationary, and wherein said first masking structure is of a thinner construction than said second masking structure.