Synthesis of Copper and Copper-Ruthenium Nanoparticles in Ionic Liquids for the Metallization of Advanced Interconnect Structures

Bimetallic nanoparticles can be used in a variety of applications such as catalysis, in advanced magnetic or optical devices or as starting materials to form continuous metallic layers. In this study, we report the synthesis of bimetallic ruthenium-copper (Ru-Cu) nanoparticles in ionic liquids. For this purpose, solutions of ionic liquids containing a mixture of precursors of Ru and Cu were decomposed under dihydrogen. Small, crystalline and well dispersed Ru-CuNPs (2.5 ± 0.6 nm) were obtained, which are significantly smaller than the pure Ru or pure CuNPs formed under the same conditions. Our analyses suggest that these NPs have a Ru core - Cu shell structure. This structure is expected from thermodynamical and kinetics data. Moreover, this could explain the dramatic size reduction observed when mixing the two metals.