Patent ID: 8289527
Filing Date: 2012-10-16
Classification: G01B,G03F

Abstract:
1. A method for determining profile parameters of a sample structure on a workpiece using an optical metrology system optimized to achieve one or more accuracy targets, the optical metrology system including an optical metrology tool, an optical metrology tool model, a profile model of the sample structure, and a parameter extraction algorithm, the profile model having profile parameters, the method comprising: setting one or more accuracy targets for profile parameter determination for the sample structure; selecting a number of rays and beam propagation parameters to be used to model the optical metrology tool, the optical metrology tool having a light source, an illumination beam, optical elements, a diffraction beam, and a detector; measuring a diffraction signal off the sample structure using the optical metrology tool, generating a metrology output signal; determining an adjusted metrology output signal using the metrology output signal and calibration data; optimizing the optical metrology tool model and the profile model using the adjusted metrology output signal and the parameter extraction algorithm; if the one or more accuracy targets are not met, adjusting the selected number of rays, the selected beam propagation parameters, and/or the profile parameters and iterating the determining the adjusted metrology output signal and optimizing the optical metrology tool model and the profile model using the adjusted metrology output signal and the parameter extraction algorithm until the one or more accuracy targets are met.