1. A method of producing an optimum critical dimension value, said method comprising: acquiring a waveform of data for a critical dimension structure; determining a stepper focus parameter for said critical dimension structure; calculating an approximate critical dimension measurement for said critical dimension structure; calibrating said data of said waveform by determining at least three best fit data parameters for improving a linearity of said waveform; combining said stepper focus parameter with said approximate critical dimension measurement and said best fit data parameters, wherein said combining removes structural bias parameters from said approximate critical dimension measurement; and generating said optimum critical dimension value from said combining, wherein said optimum critical dimension value comprises structural measurements of said critical dimension structure that are only relevant to a critical dimension of said critical dimension structure.