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Apparatus and method for optical metrology with optimized system parameters

  • US 9,879,977 B2
  • Filed: 11/06/2013
  • Issued: 01/30/2018
  • Est. Priority Date: 11/09/2012
  • Status: Active Grant
First Claim
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1. A method comprising:

  • illuminating a specimen with an illumination light from an illumination subsystem operable to generate an available illumination light having any two or more of a range of polar angles of incidence, a range of azimuth angles of incidence, a range of polarization states, and a range of illumination wavelengths;

    constraining the available illumination light to a subset of any of the two or more of the range of polar angles of incidence, the range of azimuth angles of incidence, the range of polarization states, and the range of illumination wavelengths to minimize a measurement box size and achieve a smaller measurement box size than would otherwise be achievable from the available illumination light, wherein the constraining the illumination light involves determining a subset of illumination wavelengths associated with each of a plurality of angles of incidence that minimizes the measurement box size;

    generating a plurality of output signals indicative of a response of the specimen to the illumination light, wherein each output signal is indicative of an amount of light diffracted from the specimen at a different angle of incidence; and

    determining an estimate of a structural parameter based at least in part on the plurality of output signals.

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