Atomic Layer Deposited RuO2 Diffusion Barrier for Next Generation Ru-Interconnects

Abstract

Atomic layer deposition (ALD) is a suitable technology for conformally depositing thin films on nanometer-scale 3D structures. RuO2 is a promising diffusion barrier for Ru interconnects owing to its compatibility with Ru ALD and its remarkable diffusion barrier properties. Herein, a RuO2 diffusion barrier using an ALD process is developed. The highly reactive Ru precursor [tricarbonyl(trimethylenemethane)ruthenium] and improved O-2 supply enable RuO2 deposition. The optimal process conditions [pulsing time ratio (t(O2)/t(Ru)): 10, process pressure: 1 Torr, temperature: 180 degrees C] are established for the RuO2 growth. Growth parameters, such as the growth rate (0.56 angstrom cycle(-1)), nucleation delay (incubation period: 6 cycles), and conformality (step coverage: 100%), are also confirmed on the SiO2 substrate. The structural and electrical properties of the Ru/RuO2/Si multilayer are investigated to explore the diffusion barrier performance of the ALD-RuO2 film. The formation of Ru silicide does not occur without the conductivity degradation of the Ru/RuO2/Si multilayer with an increase in the annealing temperature up to 850 degrees C, thus demonstrating that interdiffusion of Ru and Si is completely suppressed by a thin (5 nm) ALD-RuO2 film. Consequently, the practical growth behavior and diffusion barrier performance of RuO2 can serve as a potential diffusion barrier for Ru interconnects.