Patent ID: 9494868
Filing Date: 2016-11-15
CPC Classification: G03F

Claim Text:
1. A method, comprising: providing a projection objective of a lithography projection exposure apparatus, the projection objective comprising a plurality of optical elements between an object plane of the projection objective and an image plane of the projection objective, the plurality of optical elements comprising a first optical element having a refractive power, the first optical element being disposed in the projection objective at a first location; removing the first optical element from the projection objective; inserting a first spare optical element into the projection objective at the first location to compensate for degradation of one or more optical elements in the projection objective; after inserting the first spare optical element into the projection objective, adjusting an image quality of the projection objective to a desired image quality by a process which comprises: wherein a surface of the second spare optical element comprises an aspherical shape or a non-rotationally symmetric shape configured to adjust the image quality of the projection objective to the desired image quality of the projection objective.