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Process endpoint detection method using broadband reflectometry

  • US 6,979,578 B2
  • Filed: 03/27/2003
  • Issued: 12/27/2005
  • Est. Priority Date: 08/13/2002
  • Status: Expired due to Term
First Claim
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1. A method of determining a parameter of interest during processing of a patterned substrate, comprising:

  • obtaining a measured net reflectance spectrum resulting from illuminating at least a portion of the patterned substrate with a light beam having a broadband spectrum;

    calculating a modeled net reflectance spectrum as a weighted incoherent sum of reflectances from different regions constituting the portion of the patterned substrate, for wavelengths below a selected transition wavelength in the broadband spectrum, using a first optical model to calculate the reflectance from each region as a weighted coherent sum of reflected fields from thin film stacks corresponding to laterally distinct areas constituting the region;

    for wavelengths above the selected transition wavelength in the broadband spectrum, using a second optical model to calculate the reflectance from each region as a reflected field from a thin film stack obtained by replacing layers in the region with effective homogeneous mediums; and

    determining a set of parameters that provides a close match between the measured net reflectance spectrum and the modeled net reflectance spectrum.

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