A study of novel overlay targets designs
Yi‐Sha Ku, An-Shan Liu, Nigel P. Smith · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2005
We report the results of a study of grating-based target designs for overlay measurement. While improvements to measurement precision may be expected from targets with more pattern information, the main interest in these targets is the hope that they will provide more accurate measurements. In order to test the accuracy of these targets, we have compared data taken using them with data obtained from conventional bar-in-bar targets. In general, good agreement is seen. There are instances, however, where the grating targets all produce a significantly different measurement to the bar-in-bar target. Although this isn’t proof of improvements in measurement accuracy with these newer designs, it does suggest that thorough investigation is warranted.