Additive-Assisted Forming High-Quality Thin Films of Sn–Oxo Cluster for Nanopatterning

Recently, metal–oxo clusters (MOCs) have attracted
significant
interest in fabricating nanoscale patterns in semiconductors via lithography.
However, many MOCs are highly crystalline, making it difficult for
them to form films and hindering subsequent nanopatterning processes.
In this study, we developed a novel and simple method to enhance the
film-forming ability of aromatic tetranuclear Sn–oxo clusters
by adding additives. Theoretical calculations and Fourier-transform
infrared (FTIR) analysis revealed the formation of intermolecular
hydrogen bonds between the Sn–oxo clusters and additives, which
induced a crystal–gel phase transition at −20 °C,
thereby inhibiting the easy crystallization of the Sn–oxo clusters.
High-quality and uniform thin films with surface roughness below 0.3
nm were prepared via spin coating. The obtained thin films exhibited
good lithographic performance under deep ultraviolet (DUV), electron
beam, and extreme-ultraviolet irradiation without a photo acid generator/photoinitiator,
and 13- and 21 nm-wide line patterns were obtained on the films via
electron-beam and extreme-ultraviolet lithographies. This study will
pave the way for the further investigation of novel MOCs for advanced
lithography and other thin-film applications.