Patent ID: 6952271

Claim:
A method of determining the physical profile of a structure, comprising: obtaining a measured diffraction spectrum, wherein the measured diffraction spectrum is measured from radiation diffracted from the structure after being illuminated by incident radiation; comparing the measured diffraction spectrum to a plurality of simulated diffraction signals, wherein each diffraction signal has a corresponding hypothetical profile, and wherein each simulated diffraction signal was generated based on the corresponding hypothetical profile and sets of intermediate layer data, each set of intermediate layer data corresponding to a separate one of a plurality of hypothetical layers of a hypothetical profile, and each separate hypothetical layer having one of a plurality of possible combinations of hypothetical values of properties for that hypothetical layer; and determining a best-match simulated diffraction signal from the comparison of the measured diffraction signal to the plurality of simulated diffraction signal, wherein the corresponding hypothetical profile of the best-match diffraction signal is assumed to correspond to the physical profile of the structure.