Atomic InOx motif-mediated cross-linking in PMMA via sequential infiltration synthesis for negative-tone lithography

As continued device scaling demands thinner photoresists with enhanced sensitivity and etch resistance, organic-inorganic hybrid resists have emerged as promising candidates by combining the processability of polymers with the mechanical robustness of inorganic components. In this study, we investigated poly(methyl methacrylate) (PMMA)-based hybrid resists synthesized via sequential infiltration synthesis (SIS) for high-resolution electron beam lithography, focusing on how metal oxide incorporation influences resist performance. SIS was applied to PMMA films using various precursor combinations – including trimethylindium, trimethylgallium, water, and ethylene glycol – to systematically examine the impact of different metal oxides on key lithographic metrics such as sensitivity, resolution, line width roughness, and line edge roughness. Hybrid resists synthesized using different SIS precursors and cycle numbers consistently exhibit enhanced sensitivity in negative-tone lithography, with the degree of improvement depending on the specific precursor employed. Comprehensive characterization using scanning transmission electron microscopy, electron energy loss spectroscopy, micro-Raman spectroscopy, and micro-X-ray photoelectron spectroscopy supports a structural model in which metal oxide motifs function as crosslinking centers, offering new insights into the molecular design of next-generation hybrid resists.