Patent ID: 8571845

Claim:
A method implemented by a computer, the method being for obtaining a sensitivity model that predicts changes in imaging behavior due to changes in a set of tunable parameters on a corresponding lithographic apparatus, the method comprising: maintaining a lithographic process model characterizing imaging behavior of a corresponding lithographic process for a given layer of a wafer using the corresponding lithographic apparatus, given particular values for the set of tunable parameters on the corresponding lithographic apparatus; generating a simulated wafer contour in the given layer using a design layout and the lithographic process model based on a set of values of the set of tunable parameters; identifying discrepancies in the simulated wafer contour against a reference corresponding to the set of values of the set of tunable parameters; quantifying the discrepancies with a cost function; and performing iterations of the generating and identifying steps to minimize the cost function and obtain calibrated parameters of the sensitivity model, wherein a value of at least one tunable parameter of the corresponding lithographic apparatus is adjusted prior to performing each iteration, and wherein the reference for each iteration is different in accordance with the adjusted value of the at least one tunable parameter, wherein one or more of the maintaining, generating, identifying, quantifying and performing steps are implemented by the computer.