Patent ID: 8184265

Claim:
A method, comprising; conditioning a radiation beam using an illumination system; imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam using a reticle comprising a pattern image area and at least one reticle mark adjacent to the pattern image area; projecting an image of the patterned radiation beam onto a target portion of a substrate by a projection system, the substrate being held on a substrate table; illuminating the at least one reticle mark by the radiation beam to generate an aerial image of the at least one reticle mark; projecting the aerial image on an image sensor, the image sensor being arranged on the substrate table; collecting image data of the projected aerial image from the image sensor; obtaining, from the image data, positional parameters of the projected aerial image; determining an estimated magnification correction of magnification settings of the projection system from a weighted average of a measured temporal thermal expansion and a prediction of a temporal thermal expansion of the reticle; and correcting any deviation of the positional parameters from a required position of the aerial image, wherein the correction comprises compensating an illumination beam induced thermal expansion of the reticle by the estimated magnification correction.