Diffusion barrier properties of atomic layer deposited ultrathin Ta2O5 and TiO2 films

Diffusion barrier properties of ultrathin Ta2O5 and TiO2 films deposited by the atomic layer deposition (ALD) 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 pentaethoxide and water and titanium dioxide films from titanium tetramethoxide and water, both at 240 degrees C. The films examined in the diffusion barrier tests were in the thickness range of 1 - 4 nm. 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, the 3-nm-thick titanium dioxide film was found to possess the best resistance to copper diffusion as the first etch pits were observed only after the annealing at 650 degrees C.