Benchmarking EUV mask inspection beyond 0.25 NA

摘要

The SEMATECH Berkeley Actinic Inspection Tool (AIT) is an EUV zoneplate microscope dedicated to photomaskresearch. Recent upgrades have given the AIT imaging system selectable numerical aperture values of 0.25, 0.30, and0.35 (4x equivalent). The highest of which provides resolution beyond the current generation of EUV lithography re-search tools, giving above 75% contrast for dense-line features with 100-nm half-pitch on the mask, and above 70% for88-nm half-pitch. To improve the imaging system alignment, we used through-focus images of small contacts to extractaberration magnitudes and compare with modeling. The astigmatism magnitude reached a low value of 0.08 wavesRMS. We present the results of performance benchmarking and repeatability tests including contrast, and line widthmeasurements.