Lithography performance and environmental compatibility of PFOS-free photoacid generators

Abstract

Photoacid generators (PAGs) with environmentally friendly cores and partially fluorinated sulfonate salts have been synthesized and studied. The cores were based on naturally occurring compounds such as cholesterol and glucose and were functionalized with a biodegradable octafluoro-3-oxapentanesulfonate. These PAGs were soluble in common spinning solvents and lithographically characterized with poly(styrene-co-4-hydroxy-styrene-co-tert-butylacetate) photoresist, and they showed higher resolution for photoresist applications than a perfluorooctane sulfonate (PFOS)-based triphenylsulfonium salt PAG, capable of patterning 50 nm dense lines. In addition, microbial bioassays confirmed that the newly developed PAG compounds can be broken down by microorganisms commonly found in conventional wastewater treatment systems. The biodegradation potential of the new PAGs presents a distinct advantage compared to that of PAG perfluorinated structures such as PFOS and perfluorobutane sulfonate, which are highly resistant to biodegradation and difficult to treat by conventional processes. The excellent performance and environmental compatibility of these PAGs make them promising candidates for use in high-resolution lithography systems.

Photochemical Fragmentation of Irgacure PAG 103

“…Nonionic PAGs include oxime sulfonates, − oxime esters, and N -sulfonyloxyimides . The choice of PAG for an application depends upon many factors such as the wavelength of radiation, − quantum efficiency of acid generation, solubility in the casting solvent, thermal and hydrolytic stability, toxicity, strength of the liberated acid, − line width, acid diffusion, and environmental considerations. , Although the mechanism of the photochemical decomposition of Crivello salts has been studied, − less is known about how nonionic PAGs release acid. In this paper, a commercial UV light PAG called Irgacure PAG 103 − is examined and key photochemical decomposition products are characterized.…”