Patent ID: 7531369
Filing Date: 2009-05-12
Classification: G01B,G01N

Abstract:
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.