Lithographic method and apparatus

摘要

A method and apparatus are provided for determining apodization properties of a projection system in a lithographic apparatus. The method comprises allowing light from a given point in an illumination field to pass through the projection system along at least three different optical paths, and then determining the difference in the intensity of light received in a projection field from the two different optical paths, and calculating apodization properties of the projection system from the intensity difference. It is not necessary to know the intensity distribution in the illumination field. To provide the different optical paths a pinhole reticle provided with wedges of different orientations is used.

主权项

1. A method of determining apodization properties of an optical system comprising an illumination system and a projection system, the method comprising:
allowing light from a given point in an illumination field to pass through the projection system along at least a first optical path, a second optical path and a third optical path; determining a first difference in intensity of light received in a projection field from the first optical path and the second optical path; determining a second difference in intensity of light received in the projection field from the first optical path and the third optical path; and calculating apodization properties of the projection system from the first difference in intensity of light and the second difference in intensity of light.