Ligand‐Mediated Nuclearity Tuning of Tin Oxo Clusters for Advanced Lithography

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Abstract
Hybrid tin oxo clusters (SnOCs) have emerged as promising molecular resists for electron‐beam (EB) and extreme‐ultraviolet (EUV) lithography; however, their patterning mechanisms remain poorly understood due to the coupled effects of ligand electronics, cluster nuclearity, and electron‐induced fragmentation. In this study, we demonstrate a ligand‐mediated nuclearity tuning strategy that enables the selective synthesis of Sn 6 ‐ and Sn 3 ‐based clusters using electron‐donating carboxylate and electron‐withdrawing diphenylphosphinate ligands, respectively. Density functional theory calculations, electrostatic potential analysis, and bond dissociation energy evaluations show that ligand electronic properties dictate the preferred electron‐driven cleavage pathways. Sn 6 clusters predominantly undergo Sn–alkyl bond scission, whereas aromatic phosphinate ligands in Sn 3 clusters stabilize the framework and suppress ligand fragmentation. These trends are supported by XPS and TOF‐SIMS analyses, which reveal extensive alkyl cleavage and organic–inorganic crosslinking in Sn 6 ‐based resists, in contrast to minimal ligand decomposition and a robust Sn─O─P network in Sn 3 systems. As a result, Sn 6 clusters exhibit high EB sensitivity ( D 0 = 285 µC cm −2 ) and sub‐30 nm resolution, while Sn 3 clusters deliver ultra‐low line‐edge roughness (1.02 nm) and excellent pattern fidelity. This work identifies nuclearity as a chemically tunable parameter for rational molecular‐resist design.

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