The phase-shifting point diffraction interferometer has recently been developed and implemented at Lawrence Berkeley National Laboratory to meet the significant metrology challenge of characterizing extreme ultraviolet projection lithography systems. Here we present a refined version of this interferometer that overcomes the original design's susceptibility to noise attributed to scattered light. The theory of the new hybrid spatial- and temporal-domain (dual-domain) point diffraction interferometer is described in detail and experimental results are presented.
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