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.