Patent ID: 6646729
Filing Date: 2003-11-11
Classification: G03F

Abstract:
A method of determining aberration of an optical imaging system, comprising:a radiation system constructed and arranged to supply a projection beam of radiation; a support structure constructed and arranged to support a patterning device, the patterning device serving to pattern the projection beam according to a desired pattern; a substrate table constructed and arranged to hold a substrate; and a projection system constructed and arranged to project the patterned beam onto a target portion of the substrate; the method comprising: patterning the projection beam with said patterning device; measuring at least one parameter of an image formed by the projection system, for a plurality of different illumination settings of said radiation system and/or for a plurality of different numerical aperture settings of said projection system; and calculating at least one coefficient, representative of aberration of said imaging system, on the basis of said at least one parameter measured at said plurality of settings.