Etchant-Free Dry-Developable Extreme Ultraviolet Photoresist Materials Utilizing N-Heterocyclic Carbene–Metal Complexes

Extreme ultraviolet (EUV) lithography has enabled significant reductions in device dimensions but is often limited by capillary force-driven pattern collapse in conventional wet processes. Recent dry-development approaches, while promising, frequently require toxic etchants or specialized equipment, limiting their broader applicability and highlighting the need for more sustainable, cost-effective alternatives. In this study, highly reactive, etchant-free dry-developable EUV photoresists using N-heterocyclic carbene (NHC)-based metal-ligand complexes, achieving half-saturation at EUV doses of 8.5 or 27 mJ cm⁻², are synthesized. A simple thermal dry development process is employed, utilizing a standard furnace to remove unexposed areas of the photoresist, leading to 80 nm resolution with line-edge roughness (LER) comparable to wet-developed patterns. Moreover, EUV-induced chemical reactions of the NHC metal-ligand complexes are investigated via EUV-photoelectron spectroscopy, near-edge X-ray absorption fine structures, X-ray photoelectron spectroscopy, and density functional theory. It is suggested that the high EUV sensitivity of the NHC metal-ligand complexes is attributed to branching polymerization reactions initiated by secondary electron and photoelectron generation. These EUV-sensitive, dry-developable NHC metal–organic photoresists offer a sustainable and economical alternative to conventional techniques, eliminating the need for toxic and corrosive etchants while achieving high-resolution nanopatterns through simple thermal treatment, thus advancing future nanofabrication technologies.