Area-selective atomic layer deposition of ruthenium using O2 plasma-enhanced self-assembled monolayers

초록

The continuous scaling of semiconductor devices has introduced significant challenges in filling high-aspect-ratio (HAR) structures, particularly deep trenches and contact holes. Copper (Cu), the conventional material for back-end-of-line (BEOL) interconnects, faces critical reliability issues, including electromigration and a sharp resistivity increase at advanced technology nodes. This study investigates ruthenium (Ru) as a promising alternative, utilizing area-selective atomic layer deposition (AS-ALD) to achieve precise Ru deposition on SiO2 substrates. Octadecyltrichlorosilane (ODTS) self-assembled monolayers (SAMs) were employed as inhibitors to suppress Ru nucleation at non-growth regions. To facilitate dense SAM formation, O2 plasma pretreatment was applied to increase surface hydrophilicity by increasing the surface hydroxyl (–OH) group density. The optimized process promoted preferential Ru deposition in the growth region while suppressing Ru nucleation in the ODTS-covered non-growth region. Our findings demonstrate that while O2 plasma treatment effectively enhances selectivity by improving SAM adhesion, precise optimization of plasma parameters is crucial to prevent substrate damage and maintain the structural integrity of the SAM. This study highlights the potential of Ru as a reliable interconnect material for next-generation, high-performance semiconductor devices.

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