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In SITU measurement and compensation of errors due to imperfections in interferometer optics in displacement measuring interferometry systems

  • US 7,274,462 B2
  • Filed: 11/10/2004
  • Issued: 09/25/2007
  • Est. Priority Date: 09/09/2002
  • Status: Expired due to Fees
First Claim
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1. A method for determining the location of an alignment mark on a stage using an interferometry system that comprises interferometer optics configured to direct a first measurement beam to reflect from a measurement object, where either the interferometer optics or the first measurement object are attached to the stage, the method comprising:

  • measuring a location, x1, of a stage along a first measurement axis using the interferometry system;

    measuring a location, x2, of the stage along a second measurement axis;

    determining a location of the alignment mark along a third axis based on x1, x2, and a correction term, ψ

    3, calculated from predetermined information comprising information characterizing imperfections in the interferometer optics determined using the interferometry system and the stage; and

    outputting a signal from an electronic controller based on the determined location of the alignment mark.

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