Patent ID: 7421678

Claim:
A method for determining an assist feature placement, the method comprising: receiving an initial assist feature placement for a layout; receiving two or more evaluation points in the layout, wherein the evaluation points are locations in the layout where process variations are expected to affect the layout's manufacturability; determining assist feature perturbations, wherein each assist feature perturbation includes one or more modifications to assist feature geometries in the initial assist feature placement; determining perturbation values at the evaluation points in the layout using the assist feature perturbations and a process-sensitivity model, wherein the perturbation values indicate changes in the layout's sensitivity to process variations at the evaluation points; determining changes in an objective function's value using the perturbation values, wherein the objective function's value is indicative of the layout's manufacturability; using the changes in the objective function's value to select a first assist feature perturbation; determining an assist feature placement by applying the first assist feature perturbation to the initial assist feature placement; and placing assist features in the layout according to the assist feature placement, thereby improving the layout's manufacturability.