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Lithographic projection apparatus

  • US 6,348,303 B1
  • Filed: 04/12/1999
  • Issued: 02/19/2002
  • Est. Priority Date: 04/14/1998
  • Status: Active Grant
First Claim
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1. A lithographic projection apparatus comprising:

  • a radiation system, said radiation system supplying a projection beam of radiation;

    a first object table movable in at least a first direction, the scan direction, and provided with a mask holder, said mask holder holding a mask having a mask pattern;

    a second object table movable in the first direction and provided with a substrate holder, said substrate holder holding a substrate;

    a projection system constructed and arranged to image an irradiated portion of the mask onto a target portion of the substrate with a magnification M, said radiation system being adapted to supply a projection beam whose cross-section in a plane of the mask is smaller than the mask pattern, the radiation system including a movable beam masking device constructed and arranged to control the cross-section of the projection beam;

    a control unit, said control unit causing the beam masking device to be closed prior to, and open at the beginning of, a scan; and

    a compensator constructed and arranged to compensate for a variation in radiation intensity of the projection beam on the mask while the beam masking device is opening.

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