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Lithographic apparatus and device manufacturing method

  • US 7,312,846 B2
  • Filed: 08/18/2004
  • Issued: 12/25/2007
  • Est. Priority Date: 10/19/2001
  • Status: Expired due to Fees
First Claim
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1. An alignment system for aligning a substrate in a lithographic apparatus comprising:

  • an illumination system configured to illuminate a phase grating on the substrate;

    an imaging system configured to image diffracted light from said phase grating onto a reference grating substantially correctly at at least two distinct wavelengths; and

    a field stop located at an intermediate plane and configured to adjust a field of illumination on said phase grating and said reference grating,wherein said imaging system includes an optical system configured to image said phase grating onto the intermediate plane.

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