Patent ID: 7355728

Claim:
A method of optimizing an optical metrology model for a repetitive structure, the optical metrology model having profile parameters, the method comprising: a) selecting one or more profile parameters using one or more selection criteria, the one or more selection criteria including sensitivity of simulated diffraction signals to changes of the selected profile parameters and/or correlation of a selected profile parameter to other profile parameters; b) setting one or more termination criteria, the one or more termination criteria comprising measures of stability of the optical metrology model; c) characterizing the profile shape features of the repetitive structure using the one or more selected profile parameters; d) optimizing the optical metrology model using a set of values for the one or more selected profile parameters; e) determining one or more profile parameters of the profile of the repetitive structure using the optimized optical metrology model and one or more measured diffraction signals, wherein the one or more measured diffraction signals were obtained by measuring diffraction signals from an actual repetitive structure using an optical metrology device; f) calculating values of the one or more termination criteria using the one or more determined profile parameters; and g) when the calculated values of the one or more termination criteria do not match the one or more set termination criteria, revising the selection of the one or more profile parameters and/or the characterization of the profile shape features of the repetitive structure, and iterating d), e), f), and g).