Enhanced Solubility of Zirconium Oxo Clusters from Diacetoxyzirconium(IV) Oxide Aqueous Solution as Inorganic Extreme-Ultraviolet Photoresists

Metal oxo clusters have drawn a great deal of attention as the extreme-ultraviolet (EUV) photoresists. However, industrial implementation in the next-generation lithography demands further improvements in their sensitivity and resolution. In this study, a zirconium oxo cluster with methacrylate and acetate ligands was synthesized from diacetoxyzirconium(IV) oxide aqueous solution for use as EUV photoresist materials. The obtained Zr oxo cluster, consisting of a Zr core and methacrylate and acetate ligands, was similar in size to Zr6O4(OH)(4)(methacrylate)(12) cluster, but much more soluble in a variety of organic solvents. Open-frame exposure tests revealed that the Zr oxo cluster served as a negative tone photoresist with a sensitivity greater than that of Zr6O4(OH)(4)(methacrylate)(12) cluster. At a dose of 22 mJ/cm(2) in the absence of photoacid generators, the Zr oxo cluster film resolved a pattern 15 nm in width, which is sufficiently low to meet the current technological requirements.