Nonchemically Amplified Molecular Resists Based on Sulfonium-Functionalized Sulfone Derivatives for Sub-13 nm Nanolithography

In this study, a series of molecular resists based on a bis(4-butoxyphenyl) sulfone core attached to a varying number of radiation-sensitive triphenylsulfonium units (BPSSn, where n = 2, 3, and 4) were designed and synthesized. We evaluated the physical properties of these resists, including solubility, film-forming ability, and thermal stability, to assess their viability as photoresist materials. The materials allowed for negative patterning through organic development in both e-beam and extreme ultraviolet (EUV) lithography. Through manipulating the average number of triphenylsulfonium units in the molecule and optimizing the developing agents, BPSS4 resists demonstrated high resolution (16/13 nm) and low line edge roughness (2.5/2.5 nm) in e-beam and EUV dense line patterning, respectively. We further explored the EUV and e-beam exposure mechanisms of BPSS4 resist using X-ray photoelectron spectroscopy. We also investigated the outgassing behavior of the film during EUV irradiation via in situ mass spectroscopy. Remarkably, this nonchemically amplified resist exhibited high etch resistance and accurate pattern transfer capabilities. The etch durability of BPSS4 (under SF₆/O₂ plasma chemistry) with respect to the Si wafer was 21:1, highlighting its significant potential for practical applications in high-resolution lithography.