US Patent 7531369 Process endpoint detection method using broadband reflectometry
Patent 7531369 was granted and assigned to Lam Research on May, 2009 by the United States Patent and Trademark Office.
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A method of determining a parameter of interest during processing of a patterned substrate includes 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, and determining a set of parameters that provides a close match between the measured net reflectance spectrum and the modeled net reflectance spectrum. For wavelengths below a selected transition wavelength, a first optical model is used 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 transition wavelength, a second optical model based on effective medium approximation is used to calculate the reflectance from each region.
US Patent 07531369 Process endpoint detection method using broadband reflectometry US Patent 7531369 Process endpoint detection method using broadband reflectometry
US Patent 07531369 Process endpoint detection method using broadband reflectometry
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