Alkenyl/Thiol Co-Functionalized Titanium-Oxo Nanoclusters Enable Synergistic Lithography for Enhanced Resolution and Sensitivity

The lack of lithographic reactivity of titanium oxides prevents their applicability in direct nanopatterning technologies. Herein, by gradually incorporating cross-linkable alkenyl and thiol groups, we have successfully achieved the lithography applications and performance enhancement of monometallic titanium-oxo clusters (TOCs). Thereinto, by replacing the 2,2'-biphenol in a lithography-inert TOC with functional magnolol ligands, nanopatterning performance was facilitated through electron beam-induced alkenyl polymerization (from soluble cluster to insoluble cross-linked network). Moreover, thiol groups were further incorporated into the alkenyl-TOCs, giving rise to alkenyl/thiol comodified clusters. Such dual cross-linkable group functionalization brought additional thiol-ene click reactions upon exposure to enhance intercluster polymerization, which significantly improved the lithography sensitivity of TOCs, with the required exposure energy being reduced by over 70% (decreasing from >1000 μC/cm² of alkenyl-TOC to <300 μC/cm² of alkenyl/thiol-TOC). Ultimately, high-resolution 12.9 nm patterns were fabricated using alkenyl/thiol-TOCs, which are among the higher resolution levels of metal oxide cluster photoresists. This work not only reports the direct nanopatterning of titanium oxide materials but also provides a step-by-step cross-linkable group functionalization strategy to enhance their lithography applications.