Non-alkyl tin-oxo clusters as new-type patterning materials for nanolithography

Nanolithography plays crucial roles in the miniaturization of dense integrated circuit, which extremely depends on innovative resist materials. Recently, metal-containing resists have been explored due to their higher short-wavelength photon absorption than traditional polymer resists. Herein, for the first time, the patterning performance of non-alkyl tin-oxo clusters has been evaluated. Meanwhile, the influence of structural characteristics on resolution and sensitivity has been investigated. To evaluate the surface ligand effect, three non-alkyl Sn10-oxo clusters with the same core were functionalized with pyrazole, 3-methylpyrazole and 4-methylpyrazole, respectively. Furthermore, another Sn14-oxo cluster with similar core configuration was also prepared using 4-methylpyrazole ligand to study the influence of Sn nuclearity. Spin-coating method was then applied to fabricate thin films of these non-alkyl tin-oxo clusters on Si substrate, which showed various thicknesses and roughnesses. More interestingly, electron beam lithography (EBL) patterning studies indicated that for the same Sn10 core, the 4-methylpyrazole-decorated clusters showed the best performance. As for the different cluster cores with the same 4-methylpyrazole ligand, the patterns of Sn10 with the higher ligand: Sn ratio are also better than those of Sn14. Finally, distinguishable 50 nm resolution was achieved by 4-methylpyrazole-decorated Sn10 at expose energy of 100 µC/cm2 which can be significantly improved by increasing expose energy to 1,000 µC/cm2 as confirmed by atomic force microscopy (AFM) images. This work not only opens the nanolithography applications of non-alkyl tin-oxo clusters, but also provides an effective structural methodology for improving their patterning performance in future.