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Metrology method and apparatus, lithographic system and device manufacturing method

  • US 9,719,945 B2
  • Filed: 08/13/2015
  • Issued: 08/01/2017
  • Est. Priority Date: 03/27/2012
  • Status: Active Grant
First Claim
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1. A method comprising:

  • forming three or more targets on a substrate using a lithographic process;

    obtaining scatterometry measurements from the three or more targets, each of the scatterometry measurements comprising;

    a first value corresponding to an overlay in the three or more targets, anda second value corresponding to an asymmetry of a feature in a corresponding one of the three or more targets; and

    calculating an overlay error based on the scatterometry measurements and a non-linear relationship between the overlay and the scatterometry measurements, such that the second value is excluded from the calculated overlay error.

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