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.