The impact of layer thickness of IMP-deposited tantalum nitride films on integrity of Cu/TaN/SiO₂/Si multilayer structure

This work concentrates on the diffusion barrier stability of very thin tantalum nitride films with different thickness (10, 20 and 30 nm) sputter-deposited on silicon dioxide in the Cu/TaN/SiO₂/Si multiplayer structure. The impact of varying layer thickness and influence of post deposition annealing on the crystal structure, resistivity, intermixing and reactions at the interfaces were studied by using resistivity analyses, X-ray diffraction, scanning electron microscopy and Rutherford backscattering spectrometry. The results revealed that the thinner the film thickness of tantalum nitride, the more severe the reactions at the interface of copper-tantalum nitride and consumed more conductive Cu. Accelerated grain growth and/or agglomerations were also observed in all Cu surfaces. All the structures show a similar degradation process and were found to be stable up to 450°C for 35 min.