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Metrology method and inspection apparatus, lithographic system and device manufacturing method

  • US 9,140,998 B2
  • Filed: 11/10/2011
  • Issued: 09/22/2015
  • Est. Priority Date: 11/12/2010
  • Status: Active Grant
First Claim
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1. An inspection apparatus comprising:

  • an illumination arrangement operable to deliver conditioned beams of radiation to a substrate for use in measurements;

    a detection arrangement operable during such measurements to detect respective images of the substrate using radiation diffracted from the substrate, the illumination arrangement and the detection arrangement forming a measurement optical system;

    a stop arrangement within the detection arrangement, wherein the illumination arrangement and stop arrangement together are configured to select which part of a diffraction spectrum of the diffracted radiation contributes to each image;

    a controller configured to control the apparatus to produce first and second images of a periodic structure on the substrate, wherein;

    the first image is detected in a first measurement using a first selected part of the diffracted radiation, the second image is detected in a second measurement using a second selected part of the diffracted radiation, which is symmetrically opposite to the first part in the diffraction spectrum of the periodic structure without rotating the substrate; and

    wherein the detection arrangement further comprises a spatial light modulator operable to apply a varying optical attenuation over the selected part of the diffracted radiation prior to forming the first and second images respectively; and

    a computational arrangement arranged to use a difference in intensity values derived from the first and second images to determine an asymmetry-related parameter.

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