Patent ID: 7302367
Filing Date: 2007-11-27
Classification: G01B,G03F

Abstract:
1. A method for evaluating the accuracy of a library of simulated-diffraction signals for use in optical metrology of a structure formed on a wafer, the method comprising: a) obtaining a library of simulated diffraction signals; b) obtaining at least one set of four reflectivity parameters for a wavelength and/or angle of incidence of at least one simulated diffraction signal from the library; c) selecting one of the four reflectivity parameters; and d) determining a value for the reflectivity parameter selected in c) using an identity relationship for the four reflectivity parameters and values of the remaining three reflectivity parameters of the at least one set of four reflectivity parameters obtained in b); and e) comparing the value determined in d) for the reflectivity parameter selected in c) to the value in the set of four reflectivity parameters obtained in b) for the reflectivity parameter selected in c) to evaluate the accuracy of the library.