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Method and apparatus for measuring a parameter of a lithographic process, substrate and patterning devices for use in the method

  • US 10,481,503 B2
  • Filed: 08/15/2016
  • Issued: 11/19/2019
  • Est. Priority Date: 08/27/2015
  • Status: Active Grant
First Claim
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1. A method of forming a target structure and measuring a parameter of a lithographic process comprising:

  • forming a target structure comprising first and second targets by the lithographic process, wherein each of the first and second targets comprise a two-dimensional periodic structure formed in a single material layer on a substrate, and wherein the lithographic process comprises;

    defining features of grid elements in the first and second targets;

    modifying the features defined in the first target by removing portions of each grid element in the first target at predefined locations in the first target, each removed portion being offset from a grid element by a first bias amount that is close to one half of a spatial period of the features; and

    modifying the features defined in the second target by removing portions of each grid element in the second target at predefined locations in the second target, each removed portion from the second target being offset from a grid element by a second bias amount that is close to one half of the spatial period and different from the first bias amount;

    illuminating, using an optical system, the target structure with radiation;

    obtaining, using a detector, an angle-resolved scatter spectrum of the target structure; and

    deriving, using a processing device, a measurement of the parameter using asymmetry found in the angle-resolved scatter spectrum of the target structure.

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