Nonchemically amplified molecular resist based on multi-sulfonium modified triptycene for electron beam and extreme ultraviolet lithography

BackgroundTraditional chemically amplified resists (CARs) often suffer from high line-edge roughness (LER), primarily due to acid diffusion and the uneven distribution of reactive components. Nonchemically amplified resists (n-CARs) emerge as a promising solution to overcome the limitations. Molecular glasses (MGs), a type of organic compounds known for their distinct and well-defined structures, are particularly noteworthy for their homogeneity. The innovative design of MG-based n-CARs represents a significant stride toward overcoming the limitations inherent in CAR systems.AimDevelopment and performance evaluation of n-CARs utilizing the multi-sulfonium modified triptycene molecule for advanced lithography techniques, such as electron beam lithography (EBL) and extreme ultraviolet lithography (EUVL).ApproachA multi-sulfonium modified triptycene (TPESF6) was synthesized and characterized. This compound undergoes a photochemical reaction in which the sulfonium groups are transformed into thioethers, resulting in a substantial switch in polarity and thereby in solubility. The lithography performance of the TPESF6 resist was evaluated by EBL and EUVL. The lithographic patterns were analyzed by scanning electron microscopy and atomic force microscopy.ResultsTPESF6 resist demonstrated remarkable performance in EBL, achieving a 20 nm line/space (L/S) patterns as a negative-tone resist developed by water. Further evaluations using EUVL yielded an impressive 13 nm L/S pattern at a dose of 372.6 mJ/cm2 with a very low LER of 1.8 nm. Mechanistic studies show that the change in solubility of TPESF6 resist depends on the decomposition of the sulfonium cation and triflate anion groups.ConclusionsThe TPESF6 molecular resist shows high resolution and low LER, as evidenced by tests conducted using both EBL and EUVL. The integration of MG resist characteristics with the concept of n-CARs significantly improves the resolution and reduces the LER, offering a promising pathway for high-performance materials for advanced lithography.