1. A method of generating a meta-model for scatterometry analysis of a sample diffracting structure having unknown parameters, the method comprising: generating a training set by rigorously computing a spectral signal evaluation and an evaluation of the spectral signal differentiated with respect to at least one parameter across a parameter space; and training a neural network with the training set to provide reference spectral information for a comparison of the reference to spectral information recorded from the sample diffracting structure.