PFAS free chemically amplified resists enabled by low activation energy hydrocarbon cage monomers.

Advances in microelectronic devices are heavily reliant on new developments in integrated circuit design and manufacture (e.g., miniaturisation), but such modernisation also requires the associated environmental impact to be minimised. To achieve these goals, improvements in photolithography processes are critical for increasing the resolution of microfeatures. Deep ultraviolet (i.e., 193 nm) lithography remains a critical step in integrated circuit manufacture, and key resist polymers are comprised of cyclic or polycyclic (cage) saturated hydrocarbon moieties such as those derived from adamantane or norbornane. However, little to no information is available on comparative performance arising from other cage hydrocarbon structural paradigms, which places constraints on developing design principles to improve such photoresist materials. Described herein, is the synthesis and evaluation of a range of photoresist terpolymers derived from cage bicyclo, and cage tricyclo, methacrylate monomers that vary in size as compared to adamantyl methacrylate (MAdMA). The study identified that larger ring systems lower the activation barrier of carbocation formation (i.e., via hyperconjugation), which enabled photoresist deprotection using weaker non-PFAS photogenerated acids (PAGs).