| 摘要 |
A method of measuring the angular intensity distribution of an illumination beam produced by an illumination system of a lithographic apparatus includes measuring an angular intensity distribution, placing a first optical element above an object plane of the illumination system which causes light therefrom to be deflected in a first direction, and measuring the intensity distribution at said detector, placing a second optical element above said object plane which cases light from said illumination system to be deflected in a second direction, and measuring the intensity distribution at said detector, determining the change in intensity in said first and second directions, and the angular intensity distribution of said illumination beam from the measurements. There is also provided a mask for use in such a method, the mask comprising a plurality of modules, each module comprising a pinhole and an optical element mounted above the pinhole.
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