Improvement of EUV Si hardmask performance through wet chemistry functionalization

摘要

In EUV lithography, spin-on silicon hardmasks have been widely used not only as etch transfer layers, but also as assist layers to enhance the lithographic performance of resist. In this study, we demonstrate a novel approach to functionalize spin-on silicon hardmasks by hybridizing them with functional groups through a sol-gel approach. By varying the concentration and type of the functional groups, the structure and property of the hardmasks can be tuned effectively, especially in the aspects of surface energy, elemental composition, and hardness. The lithographic performance of the functionalized hardmasks was evaluated using NXE3300 EUV exposure system to print line-space features with a targeted CD = 16 nm half pitch. Evidenced by the results, when the functionalized hardmasks were used as underlayers. the resist exhibits large processing window with the printable CD ranging from 11.9 to 19.7 nm and a biased 3-sigma line width roughness = 3.73 nm. In contrast, on a non-functionalized spin-on hardmask. no feature can be printed. Finally, the CF_4 and O_2 plasma etch rates of the hardmasks were tested to evaluate the impact of functionalization on their etch-selectivity.