Atomic layer deposition of a ruthenium thin film using a precursor with enhanced reactivity

Abstract

Ruthenium (Ru) thin films were grown via atomic layer deposition (ALD) using a novel Ru precursor with enhanced reactivity, namely Ru(η⁵-cycloheptadienyl)₂ (Ru(chd)₂) and O₂. Self-limiting growth during the Ru ALD process was achieved by varying the Ru precursor and O₂ feeding times. Metallic Ru films with a low resistivity (10–16 μΩ cm) grew at deposition temperatures between 200 and 300 °C, where the growth per cycle (GPC) during Ru ALD was 0.2 to 0.4 Å cy⁻¹ at 265 °C. The Ru incubation times were considerably shorter using the novel precursor (negligible on Pt and TiN, ∼22 cycles on SiO₂) compared with those associated with Ru ALD using a high-valency Ru precursor and O₂. The characteristics of the Ru film were influenced by the substrate. Specifically, the Pt substrate gave rise to an amorphous film, while crystalline films were grown on the TiN and SiO₂ substrates, where a high RuO_x content resulted on the SiO₂ substrate.