As semiconductor LSI has become highly more integrated and its chip's pattern has become much finer, it shall be demanded in mask production to position the pattern even more accurately than ever. To meet the mask metrology requirements for future LSI designs, Nikon Corporation has developed the XY-5i. In this paper, first, we present the required accuracy for reticle and the required accuracy for the metrology system in each DRAM generation. Then we present the main specifications of the XY-5i. Second, we will explain the new technologies which are introduced so as to improve the coordinate measurement repeatability. And the performance will be demonstrated with actual measurement data from the XY-5i. Third, we will explain the new flexure compensation and the mirror bow compensation, which are introduced in order to improve coordinate nominal accuracy. The effectiveness of these compensations is shown with actual data in this paper.
"Mask metrology system XY-5i for 256-Mbit DRAM", Proc. SPIE 2512, Photomask and X-Ray Mask Technology II, (3 July 1995); doi: 10.1117/12.212760; https://doi.org/10.1117/12.212760