Tunable Positive/Negative Tone Switching in Sn-Based Extreme Ultraviolet Lithography Dry Resists: Mechanism and Sub-7 nm Patterning

Abstract As integrated circuit technology scales toward the Angstrom era, the limitations of traditional spin-coated wet photoresists—specifically regarding stochastic defects and pattern collapse—have become critical bottlenecks for high-numerical-aperture extreme ultraviolet (high-NA EUV) lithography. Consequently, dry photoresists deposited via molecular layer deposition (MLD) have emerged as a transformative solution, offering atomic-level thickness control and superior uniformity. Here, we report a tin-based hybrid dry photoresist synthesized via MLD using tetrakis(dimethylamino)tin and 2-butene-1,4-diol. A distinctive feature of this material is its tunable polarity, governed by the development modality: wet development in an ammonia solution yields a positive-tone resist, while dry development using fluorine-based inductively coupled plasma (ICP) etching results in a negative-tone profile. Under 50 keV electron beam exposure (wet development) conditions, we achieved an outstanding resolution limit of 7 nm for a single line, whilst under EUV exposure conditions, we achieved a resolution limit of 18 nm for a single line. To decode the underlying physics of this dual-tone behavior, we employed a rigorous multiscale approach combining in-situ characterization (XPS, TEM, EDS, and EUV-irradiated mass spectrometry) with density functional theory (DFT) calculations. These theoretical and experimental insights elucidate the specific bond-breaking and reorganization mechanisms driving the polarity switch. This work not only presents a high-performance candidate for next-generation lithography but also establishes a fundamental framework for the mechanistic design of advanced dry photoresists.