Iodonium functionalized polystyrene as non-chemically amplified resists for electron beam and extreme ultraviolet lithography†

A novel non-chemically amplified resist (n-CAR) based on biphenyl iodonium perfluoro-1-butanesulfonate-modified polystyrene with a naphthalimide scaffold (PSNA_0.4) was synthesized and characterized. Through extensive exploration using dose-dependent resist thickness analysis, acetonitrile was identified as the optimal developer. Employing electron beam lithography (EBL), the n-CAR of PSNA_0.4 demonstrated its high-resolution patterning capability by resolving a dense line pattern of 18 nm L/S at an exposure dose of 1300 μC cm⁻², achieving a high contrast of 7.1. Further studies using extreme ultraviolet lithography (EUVL) demonstrated that the PSNA_0.4 resist can achieve 22 nm L/S patterns at a dose of 90.8 mJ cm⁻², underscoring its high sensitivity for n-CARs. Detailed studies to gain insights into the underlying patterning mechanisms using X-ray photoelectron spectroscopy (XPS) suggest that the cleavage of polar iodonium into nonpolar polystyrene (PS)-based iodobenzene species enables a solubility switch, resulting in negative lithographic patterns. These findings highlight the innovative potential of the PSNA_0.4 resist in advancing the capabilities of n-CAR technologies, particularly in the realms of EBL and EUVL, for high-resolution lithographic applications.