Tin‐Oxo Nanocluster Composite Films as Positive‐Tone Photoresist for Extreme UV Lithography

Abstract As high‐numerical aperture extreme UV lithography (EUVL) approaches commercial deployment, driving a need for innovation in photoresist technology, extensive research has identified tin‐oxo nanoclusters (TOCs) as promising next‐generation photoresist platforms. This study proposes a method for achieving TOC‐based photoresists that increase their solubility upon exposure to EUV radiation, addressing the current lack of suitable candidates. Lewis‐acidic alkylated TOCs undergo ligand dissociation upon exposure to high‐energy electron beams or EUV light. This structural change enhances further the Lewis acidity of the resulting compounds, enabling the selective dissolution of exposed regions in a Lewis‐basic aqueous developer to form a positive‐tone stencil. This strategy is successfully demonstrated using DSBTOC , which contains bulky counter‐anions but lacked sufficient patterning performance and stability for high‐resolution pattern formation. A modified formulation combining DSBTOC with 10 wt.% dendritic hexaphenol ( DHP ) that acts as both a Lewis base and a radical scavenger exhibited improved thin‐film properties and chemical stability. EUVL testing of films made from this mixture produced a positive‐tone stencil with a line width of 13 nm. It is expected that TOC‐based positive‐tone resists to complement their negative‐tone counterparts in producing high‐performance semiconductor chips.