Patent ID: 8310686

Claim:
A method of determining the thickness, or curvature, of structures having curvature and one or more thin films, comprising the steps of: generating a beam of radiation; focusing the beam through the at least one film; measuring the intensity variations across the reflected beam in the Fourier plane; for each of a plurality of angles of reflectance corresponding to positions within the Fourier plane, (i) determining, based at least in part on parameters chosen to describe the one or more films, the paths of a plurality of rays sharing the angle of reflectance but having different angles of incidence and computing complex amplitudes of reflected light associated with the rays, and (ii) summing over the complex amplitudes associated with the paths, thereby obtaining calculated Fourier plane intensity variations; comparing the calculated Fourier plane intensity variations with the measured intensity variations; and iteratively refining the parameters so as to optimize agreement between the calculated and measured intensity variations to thereby determine the thickness or curvature of the one or more films from the angularly dependent intensity measurement.