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Measuring critical dimensions of a semiconductor structure

  • US 8,798,966 B1
  • Filed: 01/03/2007
  • Issued: 08/05/2014
  • Est. Priority Date: 01/03/2007
  • Status: Active Grant
First Claim
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1. A method of model-based optical metrology to measure a critical dimension of a grating layer, the method comprising:

  • illuminating an area of a geometrical structure of dispersive materials with incident electromagnetic radiation from an illuminator of a scatterometer apparatus, wherein the incident electromagnetic radiation is polarized;

    measuring spectral components of the incident electromagnetic radiation reflected from the area using a detector of the scatterometer apparatus; and

    using a computer for the scatterometer apparatus to determine parameter values for the semiconductor structure that minimize an objective function J which depends on differences between the measured spectral components and computed spectral components based on a parameterized geometrical model of the geometrical structure,wherein steps for determining the parameter values that minimize the objective function include;

    computing ∇

    pJ where p is a parameterized vector of the parameter values, wherein the parameter values comprise ƒ and

    h, where h is a height of the grating layer, and ƒ

    is a critical dimension fraction comprising the critical dimension divided by a pitch of the grating layer.

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