Diffusion barrier properties of 10nm Ru sputtered in N and Ar atmospheres have been assessed. N was found to be dissolved in the Ru film deposited in N atmosphere making it amorphous with ten times higher sheet resistance. Annealing caused effusion of N resulting in crystallization of Ru and a sharp decrease in sheet resistance. The incorporation of N delayed the Ru silicide formation and reduced Cu and Ru diffusion into the SiO2 dielectric layer. These beneficial performances are attributed to dissolved N in the amorphous films and to N grain boundary stuffing in crystallized films.
Ru is examined as a barrier/seed layer in different layer stacks, with and without Ta, for a Cu/low-system. Ru was found to promote a more pronounced Cu͑111͒ texture than Ta, and the texturing appears to increase with the increase of the Ru-layer thickness. Physical-vapor-deposited Cu films on both Ru and Ru/Ta layers are adequately smooth with root-mean-square roughness of ϳ0.8-1.4 nm. Ru crystals on a low-layer have a columnar microstructure. Cu and Ru diffusion into the low-occurred after thermal annealing at 300°C for 1 h. A four-point bend adhesion study demonstrates a sufficiently high Ru/low-adhesion strength ͑ϳ6 J/m 2 ͒ in comparison to Ta/low-͑ϳ6.5 J/m 2 ͒.
The reaction mechanisms and related microstructures in the Cu/Si, Ru/Si, and Cu/Ru/Si metallization system were studied experimentally. With the help of sheet resistance measurements, x-ray diffraction, field-emission scanning electron microscopy, secondary ion mass spectroscopy, and transmission electron microscopy, the metallization structure with Ru barrier layer was observed to fail completely at temperatures around 700 °C, regardless of the Ru thickness because of the formation of polycrystalline Ru2Si3 followed by Cu3Si protrusions.
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