Simulations were made of the combined, lattice and grain-boundary, diffusion of impurities in thin-film diffusion barriers for semiconductor device metallizations. The calculated results for impurity concentration profiles demonstrated quantitatively that there had been an obvious underestimation, of the frequently used 2-dimensional analysis, with regard to the effects of the film geometry and grain-boundary diffusion coefficient. In the case of the average concentration at the reverse side of diffusion barriers, a factor of 2 difference was found between the 2-dimensional and 3-dimensional results over relevant ranges of times and grain sizes. Graphs were provided for the prediction of the effectiveness of diffusion barriers. The particular example of Al diffusion in TiN films justified the use of this material as an effective diffusion barrier in Si devices.

X.Gui, S.K.Dew, M.J.Brett: Journal of Electronic Materials, 1994, 23[12], 1309-14