Method and apparatus for controlling a lithographic apparatus

摘要

A lithographic exposure process is performed on a substrate using a scanner. The scanner comprises several subsystems. There are errors in the overlay arising from the subsystems during the exposure. The overlay errors are measured using a scatterometer to obtain overlay measurements. Modeling is performed to separately determine from the overlay measurements different subsets of estimated model parameters, for example field distortion model parameters, scan/step direction model parameters and position/deformation model parameters. Each subset is related to overlay errors arising from a corresponding specific subsystem of the lithographic apparatus. Finally, the exposure is controlled in the scanner by controlling a specific subsystem of the scanner using its corresponding subset of estimated model parameters. This results in a product wafer being exposed with a well controlled overlay.