Diffusion barrier properties of ultra-thin Ta2O5 and TiO2 films deposited by the atomic layer deposition method were investigated. The oxide films were deposited using well-defined deposition processes with metal alkoxides and water as precursors. Tantalum oxide films were deposited from tantalum penta-ethoxide and water and titanium dioxide films from titanium tetramethoxide and water, both at 240C. The films examined in the diffusion barrier tests were in the thickness range of 1 to 4nm. The breakdown temperatures of the annealed Cu/barrier/Si structures were determined from the increase in the sheet resistance, X-ray diffraction data, and etch-pit test results. From the studied barrier films, a 3nm-thick titanium dioxide film was found to possess the best resistance to Cu diffusion, as the first etch pits were observed only after annealing at 650C.

Diffusion Barrier Properties of Atomic Layer Deposited Ultrathin Ta2O5 and TiO2 Films. Alén, P., Vehkamäki, M., Ritala, M., Leskelä, M.: Journal of the Electrochemical Society, 2006, 153[4], G304-8

Figure 4

Diffusivity of Zr in rutile

a: perpendicular to c-axis, b: parallel to c-axis