Comparison of EUV Photomask Metrology Between CD-AFM and TEM

Abstract Accurate metrology of extreme ultraviolet (EUV) photomask is a crucial task. In this paper, two different methods for reference EUV are compared. One the critical dimension atomic force microscopy (CD-AFM). measurements, contribution its AFM tip geometry usually dominant error source, as measured images dilated results structures by geometry. To solve problem, bottom-up approach has been applied in calibrating (effective) where result traceably calibrated to lattice constant silicon crystals. The other transmission electron (TEM). For achieving measurement traceability, structure features pairs TEM images; thus distance between pair metrological prior can be determine magnification image. study, selected CD-AFM, and then sample prepared high-resolution nearly at same location. Of six feature groups compared, agree well within uncertainty, indicating excellent performance developed methodology. This research supports development standard, which “reference ruler” with improved low uncertainty fabs.