High-Throughput Precursor Screening in the Molecular Layer Deposition of EUV Photoresists

Hybrid molecular layer deposition (MLD), the vapor-phase layer-by-layer process for depositing organic-inorganic films with subnanometer thickness and compositional control, has seen growing interest for use in the creation of photoresists for extreme ultraviolet (EUV) photolithography. MLD is well-suited for this purpose, as the wide variety of available reactants allows for the creation of thin films with tunable EUV absorptivity, air stability, etch resistance, and mechanical stability. However, while recent work to create patternable films primarily explored the impact of changing the inorganic element, such as Al and Sn, on film properties, the influence of the organic reactant on the final photoresist properties remains largely underexplored. Using our previously published high-throughput multi-chamber MLD system, we investigated the stability and mechanical properties of organic-inorganic hybrid thin films designed for EUV lithography applications. Eighteen different film chemistries were synthesized using combinations of three organometallic precursors—diethyl zinc, trimethylaluminum, and tin(IV) t-butoxide—and six organic precursors. These films were evaluated for stability in air, developer compatibility, and etchant resistance, both before and after UV exposure, while film transformations were monitored using Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Selected materials demonstrating high performance with UV exposure also underwent patterning tests using an electron beam source, with results visualized via Scanning Electron Microscopy. Our findings reveal that specific combinations of organic and inorganic components yield films with significantly improved mechanical properties, stability in air, and patternability. This research provides insight into desirable properties of organic precursors needed to create superior EUV photoresists using MLD.