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Lithographic apparatus, device manufacturing method, and device manufactured thereby

  • US 6,721,036 B2
  • Filed: 04/06/2001
  • Issued: 04/13/2004
  • Est. Priority Date: 04/10/2000
  • Status: Expired due to Term
First Claim
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1. A lithographic projection apparatus comprising:

  • a radiation system for supplying a projection beam of radiation;

    a support structure for holding patterning structure, the patterning structure serving to pattern the projection beam according to a desired pattern;

    a substrate table for holding a substrate;

    a projection system for projecting the patterned beam onto a target portion of the substrate;

    a level sensor for measuring at least one of a perpendicular position and tilt about at least one parallel axis of a surface of an object held by one of the support structure and the substrate table, and generating a position signal indicative thereof, perpendicular referring to a direction substantially perpendicular to the said surface and parallel referring to a direction substantially parallel to said surface;

    a servo system responsive to said position signal for moving said object to a desired position; and

    a filter connected between said level sensor and said servo system for filtering said position signal, the filter having a transfer function representative of a difference between an actual measurement of the level sensor and an ideal measurement of the level sensor.

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