Synthesis and Characterizations of a Nonalkyl Tin Oxo Cluster and its Application as High EUV Absorption Coefficient and Etch Resistant Inorganic Resist for EUV Lithography

We introduce a novel nonalkyl tin oxo cluster, CNU-TOC-01(4C-C), synthesized through a reflux-based solution reaction using SnCl₂, H₂O, and pyrazole, which permits scalable production and molecular customization. Using field desorption-time-of-flight mass spectrometry (FD-TOF MS) and small-angle X-ray scattering (SAXS), CNU-TOC-01(4C-C) is characterized as a cyclic cluster with the molecular formula Sn₄Cl₃(C₃N₂H₄)(C₃N₂H₃)H₄O₈. The cluster size was measured to be 11.6 Å by SAXS and estimated to be 11.1 Å lengthwise in quantum chemical calculation. The synthesized material exhibits an extreme ultraviolet (EUV) linear absorption coefficient of 20.7 μm^-1. Initial application in EUVL and electron beam lithography (EBL) achieved fine line and space patterns with the potential for ultrafine resolutions upon optimization. CNU-TOC-01(4C-C)'s high etch resistance underscores its exceptional suitability as an advanced resist material for future lithographic applications.