Repair specification study for half pitch 32-nm patterns for EUVL Hajime Aoyama*, Tsuyoshi Amano, Yasushi Nishiyama, Hiroyuki Shigemura, and Osamu Suga

摘要

One of the key issues in extreme ultraviolet lithography (EUVL) is the influence of defects on a mask because of the high printing resolution of EUVL. In order to address this issue, it is necessary to estimate the critical size of an absorber pattern defect and that of a repaired defect. The repair of an opaque defect by milling or of a clear defect by deposition might not be perfect; so the area, height, and optical constant of the repair material must be taken into consideration By estimating the threshold of calculated aerial images, the critical dimension (CD) that can be printed was found to equal the square root of the defect area. For the repair of opaque defects, residual Ta was found to be more likely to cause poor printing than the etching of the multilayer by excessive milling. Since a clear defect is repaired with Ta with the same optical properties as the absorber material, the CD error in printing is mainly caused by the repair of a CD error and is not caused by an error in height that is less than +25% of the height of the Ta absorber. The optimal optical constant of the repair material was estimated by varying the refraction coefficient from 0,9199 to 0.9999 and the extinction coefficient form 0.0001 to -0 0451 We found that carbon is a useful repair material that provides a CD error of at most ±0.5 nm around a defect with an area of 64 nm because the maximum refraction should be below 0.97.