| US 7,531,369 B2 | ||
| Process endpoint detection method using broadband reflectometry | ||
| Vijayakumar C. Venugopal, Berkeley, Calif. (US) | ||
| Assigned to Lam Research Corporation, Fremont, Calif. (US) | ||
| Filed on Aug. 12, 2005, as Appl. No. 11/203,365. | ||
| Application 11/203365 is a continuation of application No. 10/401118, filed on Mar. 27, 2003, granted, now 6,979,578. | ||
| Prior Publication US 2006/0035395 A1, Feb. 16, 2006 | ||
| Int. Cl. H01L 21/66 (2006.01) | ||
| U.S. Cl. 438—14 | 17 Claims |
| 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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