Increasing the sensitivity of a non-chemically amplified molecular resist by cascade esterification†

A molecular glass functionalized with γ-hydroxy carboxylate and triphenylsulfonium groups (ADTPS) was successfully synthesized and characterized. The solubility, thermal stability, and film-forming ability of the molecular glass were evaluated, confirming the feasibility of using it as a resist material. The lithographic performances of the ADTPS resist were studied by electron beam lithography (EBL) and extreme ultraviolet lithography (EUVL). It exhibited a high sensitivity for EBL with a dose-to-clear of only 145 μC cm⁻². A line/space (L/S) down to a 22 nm resist pattern was achieved by EBL. The ADTPS resist was further evaluated by EUVL, achieving performance down to a 20 nm HP pattern at a dose of 13.3 mJ cm⁻², which is more than 10 times higher than that of most triphenyl sulfonium-based non-chemically amplified resists (n-CARs). The increasing sensitivity is attributed to the occurrence of cascade esterification, which produces a subsequent lactone or ester and leads to an enormous change in solubility. The ADTPS molecular resist significantly improves the sensitivity, offering a promising pathway for the design and development of high-sensitivity molecular n-CARs.