Tuning Aluminum Precursors for Area-Selective Infiltration into Polymers for High-Precision Pattern Transfer

Over recent decades, the semiconductor industry has made remarkable progress in achieving nanoscale device dimensions, yet continuous downscaling remains challenging due to limitations in resist performance and patterning precision. Although extreme ultraviolet (EUV) lithography enables the fabrication of sub-10 nm features, stochastic variations and overlay inaccuracies increasingly hinder reliable pattern transfer at these dimensions. These issues primarily stem from the limited etch selectivity and chemical stability of current resist materials. Integrating inorganic materials into organic resists can enhance their etch selectivity during pattern transfer. In this work, we explore a pathway for high-precision patterning on monolayer polymer brushes using area-selective deposition (ASD) coupled with vapor phase infiltration (VPI) to create thin metal oxide patterns within surface modification layers comprising patterned alternating regions of polypeptoid (PPd) and polystyrene (PS) monolayer brushes. For area-selective vapor phase infiltration (AS-VPI), PPd acts as a growth promoter while PS serves as a deposition inhibitor. AS-VPI achieves approximately fourfold greater AlOx formation on PPd compared to a conventional ALD process. Precursor molecular size and ligand type effects on selective infiltration are systematically investigated using four aluminum (Al) precursors: trimethylaluminum (TMA), triethylaluminum (TEA), triisobutylaluminum (TIBA), and dimethylaluminum isopropoxide (DMAI). X-ray photoelectron spectroscopy reveals that precursor structure and ligand chemistry play critical roles in determining infiltration selectivity via their influence on precursor-polymer interactions. TMA exhibits higher differentiation of AlOx growth between PPd and PS, leading to dense and uniform oxide films on PPd, while TEA shows partial miscibility within PS, resulting in less continuous oxide formation. The bulkier TIBA and DMAI precursors show limited infiltration due to steric hindrance and dimerization, producing negligible AlOx growth. These findings highlight precursor-polymer interactions during AS-VPI. The resulting AlOx films deposited from TMA and TEA enable successful pattern transfer, demonstrating a viable bottom-up strategy for improving pattern transfer performance.