Enhanced Functional Properties of ABC-type Atomic Layer Deposited Ru Thin Films for Advanced Cu Alternative Nanoscale Interconnects

Abstract

Atomic layer deposition (ALD) technology requires high-temperature processes to achieve low resistivity, large grain size, and fewer impurities in ultrathin interconnects; however, the thermal stability of the precursor often constrains this approach. This study presents a novel ABC-type ALD process, using [tricarbonyl(trimethylenemethane)ruthenium, [Ru(TMM)(CO)3]] as the Ru precursor and two counter-reactants (O2 and NH3) sequentially, to deposit highly conductive ruthenium (Ru) thin films at a high temperature of 310 °C. A key innovation of this work is that grain growth occurs without the need for annealing. Compared to the conventional AB-type Ru ALD process, the ABC-type process significantly reduces resistivity from 20.1 μΩ·cm to 13.4 μΩ·cm. In addition to resistivity reduction, the process also improves surface roughness and reduces impurities in the Ru film. Using the Fuchs-Sondheimer and Mayadas-Shatzkes' model, the study quantitatively identifies the contribution of various factors to achieving low resistivity, highlighting grain size as the critical factor for this achievement. Moreover, machine learning potential (MLP) analysis was used to explore the adsorption and decomposition mechanisms of NH3, providing valuable theoretical insights that support the chemical rationale behind the surface reactions. Finally, the Ru thin films deposited by the ABC-type Ru ALD process achieve excellent step coverage on high-aspect-ratio trench patterns (~30, opening width: 140 nm), presenting a breakthrough approach for next-generation nanoscale interconnects.