Patent ID: 7829249

Claim:
A device manufacturing method in which an image of a given pattern comprising features having a critical dimension is projected onto a substrate using a projection system having at least one optical element that is sensitive to heat, the method comprising: determining variations in the critical dimension of the features that would be expected to occur when projecting the image at a nominal dose due to heating of the optical element; determining dose corrections to vary the critical dimension of the features to at least partially compensate for the expected variations in the critical dimension; and projecting an image of the pattern onto the substrate while applying the determined dose corrections to the image by controlling at least one of the group consisting of: an output of a radiation source, a variable attenuator, an exposure duration, a device configured to vary intensity of a radiation beam across a length of an illumination slit, a width of an illumination slit, a scan speed, movement, within a field of the image, of a neutral density filter having a non-uniform absorption pattern, and a dynamically-adjustable slit.