US 7,321,433 B2 | ||
Method and apparatus for optically measuring the topography of nearly planar periodic structures | ||
Niels Agersnap Larsen, Lyngby (Denmark); and Poul-Erik Hansen, Farum (Denmark) | ||
Assigned to Dansk Fundamental Metrologi A/S, Lyngby (Denmark) | ||
Appl. No. 10/521,009 PCT Filed Jul. 01, 2003, PCT No. PCT/DK03/00457 § 371(c)(1), (2), (4) Date Oct. 31, 2005, PCT Pub. No. WO2004/008069, PCT Pub. Date Jan. 22, 2004. |
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Claims priority of provisional application 60/395324, filed on Jul. 12, 2002. | ||
Prior Publication US 2006/0176493 A1, Aug. 10, 2006 | ||
Int. Cl. G01B 11/14 (2006.01); G01B 11/24 (2006.01); G01B 11/06 (2006.01) |
U.S. Cl. 356—601 [356/625; 356/394; 356/369; 250/372; 250/339.02; 702/189; 702/179] | 48 Claims |
1. An apparatus for measuring geometrical profiles of periodic microstructures of a sample, the apparatus comprising
a light source for emission of a light beam,
polarizing means for polarizing the emitted light beam,
focusing means for focusing the polarized light beam on the microstructures of the sample so as to provide, at a number of
microstructures, a plurality of illumination angles simultaneously,
a collection means for collecting light diffracted from the illuminated microstructures, the collection means being adapted
to collect both the 0'th and higher diffraction orders,
resolving means for resolving the collected light into diffraction data relating to illumination angles, polarization angles,
diffraction orders, and illumination wavelengths, and
a reconstruction algorithm for determining the geometrical profile of the illuminated microstructures, the reconstruction
algorithm being adapted to perform the following steps:
comparing the resolved diffraction data with modeled diffraction data from a known geometrical profile, the comparison taking
both the 0'th and higher diffraction orders into account, the known geometrical profile being selected from a database of
pre-defined families of profiles, the selection being performed using minimum norm techniques,
repeating adjusting the geometrical profile of the known selected geometrical profile until the modeled diffraction data matches
the resolved diffraction data within predetermined tolerances.
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