Area-Selective Atomic Layer Deposition of Ru Using Phenyl Silane Inhibitors: Comparison between Amino and Methoxy Head Groups

Continuous device scaling has driven the demand for nanoscale patterning, where area-selective atomic layer deposition (AS-ALD) offers a promising bottom-up alternative to conventional lithography. Here, we investigate small molecular inhibitors (SMIs), tri(dimethylamino)phenylsilane (TDMAPS) with an aminosilane headgroup and trimethoxyphenylsilane (TMPS) with a methoxysilane headgroup, for selective Ru ALD. Combined density functional theory simulations and experimental analysis reveal that the headgroup chemistry plays a pivotal role in determining inhibition performance. On SiO2, both SMIs react via condensation with surface –OH groups, but TDMAPS follows a kinetically favorable pathway with lower activation energies, enabling rapid and robust passivation. On Cu, the two SMIs follow distinct pathways that prevent stable passivation, enabling Ru thin film growth. TDMAPS tends to desorb due to its high kinetic barriers, while TMPS undergoes decomposition through an energetically accessible pathway. Consequently, TDMAPS sustained perfect selectivity (S = 1.00) up to 150 cycles on SiO2/Cu, whereas TMPS allowed gradual nucleation of Ru with S decreasing from 1.00 to 0.25. These findings demonstrate that aminosilane-based inhibitors are superior to methoxysilane analogues in both kinetics and durability, providing valuable design principles for inhibitor-assisted AS-ALD in nanoscale patterning applications.