As lens aberrations are continuously reduced, the effects of imperfections in the pupil fill, or the partial-coherence pattern produced by the illuminator of a lithographic tool, are rising up out of the noise level and becoming important. Imperfections in the pupil fill of Nikon S204-generation scanners were previously measured and found to have minimal lithographic effect. Now, pupil-fill effects in new-generation high-NA scanners have been measured and characterized. We present a systematic study of pupilgrams, measured with a pinhole reticle while exercising illuminator adjustments, and correlate them with simultaneous measurements of CD uniformity and V-H bias to evaluate the importance of the illuminator in overall CD performance. We also present two novel analysis schemes that are used to assess the pupilgrams and are shown to be reasonable predictors of CD performance.
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