An Ether-Containing Hafnium–Diethylene Glycol Dry Resist Prepared by Molecular Layer Deposition for Mild-Acid Development

Advanced lithography, including electron beam lithography (EBL), X-ray lithography (XRL), and extreme ultraviolet lithography (EUVL), imposes stringent requirements on photoresists in resolution, sensitivity, and process compatibility, thereby driving the development of metal-containing hybrid resists and vapor-phase deposition strategies. However, existing Hf-based dry hybrid photoresists often struggle to provide sufficient dissolution contrast for clean pattern formation under mild development, as unexposed regions are not fully removed. In this work, an ether-containing hafnium-based photoresist was fabricated by molecular layer deposition (MLD). Incorporation of the diethylene glycol (DEG)-derived ether unit modifies the local coordination environment of the hybrid film and enhances the removability of the unexposed regions, enabling removal in 0.1 M HCl. FTIR and XPS analyses reveal that exposure disrupts Hf-O-C coordination motifs and converts the initial hybrid network into a more HfOx-rich, less soluble framework. This combination of enhanced solubility in the unexposed regions and exposure-induced stabilization in the exposed regions establishes sufficient dissolution contrast for mild-acid negative-tone development. E-beam tests show a critical dose of approximately 250 μC·cm−2 and reproducible patterning down to 50 nm. These results identify DEG-mediated ether incorporation as an effective route to improving developer compatibility in Hf-based MLD dry resists.