Optimization strategy for epoxy cross-linked molecular glass photoresist in EUV lithography

The development of new resist materials is vital for fabrication techniques for next-generation microelectronics. A class of photosensitizer compositions with reactivity differences has been developed that can be used in epoxy cross-linked photoresist formulations for advanced microlithography techniques like extreme ultraviolet lithography (EUVL). With "PDN first, PAG second" combination strategy containing slow photolysis initiators (photoacid generator, PAG) and fast photolysis terminators (photodegradable nucleophile, PDN), photoresists produce photolithographic patterns with dense structure that are insoluble in the developer by epoxy cationic polymerization. This combination enhances chemical contrast between the exposed and non-exposed areas while eliminating the stochastic impact to get a lithographic structure with high mechanical strength. Lithographic formulations have been developed and tested in line-and-space patterning experiments using EUVL, and 18 nm half-pitch (HP) at a dose of 25.2 mJ·cm−2 with a line edge roughness (LER) of 2.8 nm was achieved by the combination strategy. This strategy offers the possibility of achieving higher resolution for photoresists based on a cationic polymerization mechanism.