Patent ID: 9612540
Date: 2017-04-04
CPC Classifications: G03F

Claim:
1. A method of operating a microlithographic apparatus comprising an illumination system which comprises an array of reflective optical elements, each reflective optical element being tiltable by a title angle around a tilt axis, the illumination system configured to produce a light irradiance distribution on the array for reflective optical elements that are illuminated, the light irradiance distribution for the illuminated reflective optical elements varying by at least 50% along a first line, the method comprising: a) specifying: i) a scan integrated target angular light distribution for a point that moves through an illumination field of the illumination system along a second line extending parallel to a scan direction of the microlithographic apparatus; and ii) a scan integrated target light energy for the point, the second line being an image of the first line; b) determining a group of the reflective optical elements through which the first line extends; c) determining tilt angles of the reflective optical elements of the group so that a scan integrated real angular light distribution for the point and a scan integrated real light energy for the point approximate the target angular light distribution for the point and the target light energy for the point, respectively; d) setting the tilt angles determined in c); and e) producing the light irradiance distribution on the array for the illuminated reflective optical elements.