Tuning surface reactivity pathways through molecular inhibitor redosing for precision nanopatterning

Area-selective atomic layer deposition (AS-ALD) has emerged as a promising bottom-up approach for achieving precise 3D patterning in advanced nanofabrication. In this study, Ru AS-ALD on SiO₂versus Si₃N₄ surfaces was investigated using cyclohexane carboxaldehyde (CHAD) as a small molecule inhibitor (SMI). CHAD exhibited selective adsorption on Si₃N₄, enabling the selective deposition of Ru when tricarbonyl-(trimethylenemethane)-ruthenium (TRuST) and H₂O were used as the precursor and reactant, respectively. A re-dosing strategy, validated by Monte Carlo (MC) simulations, was introduced to improve deposition selectivity. Compared to a single dose of CHAD, which showed selectivity against Ru for 7 nm (50 cycles), the re-dosing strategy improved the selectivity up to 27 nm (200 cycles). This improvement of selectivity was mainly due to high inhibitor adsorption density, which reduced unoccupied adsorption sites that could act as nucleation sites for precursors. The Ru AS-ALD optimized using the re-dosing strategy was applied to 2D line patterns and 3D trench patterns, consisting of SiO₂/Si₃N₄. 2D patterns achieved 26.5 nm (200 cycles) of selective deposition, accompanied by an undesirable lateral growth of 18.8 nm. Conversely, 3D patterns achieved 15 nm (100 cycles) of selective growth without lateral growth observation. The critical growth difference is mainly attributed to the surface topology: 3D trench structures provide a more effective physical and chemical barrier compared to 2D structures. Consequently, the results collectively demonstrate the potential of the re-dosing strategy in selectivity improvement and the critical role of topography in achieving reliable AS-ALD for 3D nanofabrication.