Patent ID: 8237913
Filing Date: 2012-08-07
Classification: G03F

Abstract:
1. A lithographic method, comprising: providing, using an illumination system comprising an array of individually controllable elements, a beam of radiation having a specific illumination mode; imparting the beam of radiation with a pattern in the beam's cross-section to provide a patterned radiation beam; projecting, using a projection system, the patterned radiation beam onto a substrate; obtaining information on an optical aberration of the patterned beam of radiation traversing the projection system; comparing a time dependency of the information on the optical aberration to respective modeled time dependencies, wherein the modeled time dependencies are represented by one or more Zernike coefficients and are summed over two or more orders of aberration to determine an image parameter; estimating respective model parameters based on the comparing; adjusting, based on the estimated model parameters, the individually controllable elements to control the illumination mode after projecting the pattern onto the substrate, the adjusting being carried out in a manner to reduce an effect of an optical aberration on the projected pattern due to lens heating during projection of the pattern onto a subsequent substrate; and subsequent to the adjusting, projecting the pattern onto the subsequent substrate.