Sulfonium-Functionalized Polystyrene-Based Nonchemically Amplified Resists Enabling Sub-13 nm Nanolithography

Nonchemically amplified resists based on triphenyl sulfonium triflate-modified polystyrene (PSTS) were prepared by a facile method of modification of polystyrene with sulfonium groups. The uploading of the sulfonium group can be well-controlled by changing the feed ratio of raw materials, resulting in PSTS_0.5 and PSTS_0.7 resists with sulfonium ratios of 50 and 70%, respectively. The optimum developer (methyl isobutyl ketone/ethanol = 1:7) is obtained by analyzing contrast curves of electron beam lithography (EBL). PSTS_0.7 exhibits a better resolution (18 nm half-pitch (HP)) than the PSTS_0.5 resist (20 nm HP) at the same developing conditions for EBL. This novel resist platform was further evaluated by extreme ultraviolet lithography, and patterning performance down to 13 nm HP at a dose of 186 mJ cm^-2 with a line edge roughness of 2.8 nm was achieved. Our detailed study of the reaction and patterning mechanism suggests that the decomposition of the polar triflate and triphenyl sulfonium groups into nonpolar sulfide or polystyrene plays an important role in the solubility switch.

Molecular Glass Resists Based on Tetraphenylsilane Derivatives: Effect of Protecting Ratios on Advanced Lithography

A series of t-butyloxycarbonyl (t-Boc) protected tetraphenylsilane derivatives (TPSi-Boc _x , x = 60, 70, 85, 100%) were synthesized and used as resist materials to investigate the effect of t-Boc protecting ratio on advanced lithography. The physical properties such as solubility, film-forming ability, and thermal stability of TPSi-Boc _x were examined to assess the suitability for application as candidates for positive-tone molecular glass resist materials. The effects of t-Boc protecting ratio had been studied in detail by electron beam lithography. The results suggest that the TPSi-Boc _x resist with different t-Boc protecting ratios exhibit a significant change in contrast, pattern blur, and the density of bridge defect. The TPSi-Boc_70% resist achieves the most excellent patterning capability. The extreme ultraviolet (EUV) lithography performance on TPSi-Boc_70% was evaluated by using the soft X-ray interference lithography. The results demonstrate that the TPSi-Boc_70% resist can achieve excellent patterning capability down to 20 nm isolated lines at 8.7 mJ/cm² and 25 nm dense lines at 14.5 mJ/cm². This study will help us to understand the relationship between the t-Boc protecting ratio and the patterning ability and supply useful guidelines for designing molecular resists.