Patent ID: 7023549

Claim:
A method for measuring one or more parameters of a diffracting structure, comprising: directing a beam of polychromatic electromagnetic radiation to the structure; collecting radiation from the beam after it has been modified by the structure; detecting reflectance or transmittance parameters and ellipsometric parameters of the collected radiation at a number of wavelengths; and deriving the one or more parameters from the detected parameters, said structure situated on and/or below one or more layers of material, said method further comprising providing a gallery of a plurality of profile types, each profile type and the one or more layers associated with a set of one or more parameters and a set of radiation data, wherein at least one of said profile types provided is associated with a plurality of sets of radiation data of different radiation parameters, said radiation parameters including reflectance or transmittance parameters and ellipsometric parameters; said method further comprising: selecting a profile type from the gallery; selecting at least one set of radiation data from the sets of radiation data of different parameters associated with the selected profile type based on sensitivity of such data to a change in the one or more parameters of the profile type and/or of the one or more layers; and wherein said deriving includes comparing the detected parameters to the set selected to arrive at a set of value(s) of the one or more parameters of the profile type and/or of the one or more layers.