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Process endpoint detection method using broadband reflectometry

  • US 7,531,369 B2
  • Filed: 08/12/2005
  • Issued: 05/12/2009
  • Est. Priority Date: 08/13/2002
  • Status: Expired due to Fees
First Claim
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1. A method of determining a vertical dimension of a feature in a portion of a patterned substrate during processing of the patterned substrate, the method comprising:

  • obtaining a measured net reflectance spectrum resulting from illuminating at least the 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 of the different regions as a weighted coherent sum of reflected fields from thin film stacks corresponding to laterally distinct areas constituting the region;

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

    extracting the vertical dimension of the feature in the portion of the patterned substrate from the set of parameters.

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