Patent ID: 7301649
Filing Date: 2007-11-27
Classification: G01N,G02B

Abstract:
1. An apparatus for finding a value of one or more parameters of a diffracting structure wherein a measurement is carried out by directing a polychromatic beam of electromagnetic radiation at said diffracting structure and detecting corresponding intensities of a diffraction of said beam at a number of wavelengths from said structure, comprising: a system carrying out a measurement of the structure to obtain measured intensities of a diffraction from the structure; and a processor providing a set of intensity data of the diffraction at the wavelengths corresponding to a first set of values of said one or more parameters, and performing an optimized estimation within a neighborhood of the set of intensity data using said measured intensities to arrive at a second set of values of the one or more parameters; wherein said processor generates a library of sets of intensity data of the diffraction at the wavelengths, wherein each set of data is generated assuming a corresponding set of values of the one or more parameters, said sets of values of the one or more parameters covering expected ranges of the one or more parameters; and wherein said processor compares the measured intensities to the sets of intensity data to find the set of intensity data that corresponds to the first set of values of said one or more parameters.