Two kinds of reactively evaporated nitride film with columnar (Bo) or fine-grained (B+) structures were considered as diffusion barriers to Al diffusion. The Al diffusion profiles were determined, by means of 2MeV 4He+ Rutherford back-scattering spectrometry, at temperatures of up to 550C. It was found that the diffusivity between 300 and 550C could be described by:

D (m2/s) = 3 x 10-18exp[-30/RT]

in the case of Bo layers, and by:

D (m2/s) = 1.4 x 10-16exp[-48/RT]

in the case of B+ layers (table 161). The activation energies indicated the operation of a grain boundary diffusion mechanism. The difference between the diffusion values was governed by the microstructure of the layers. Thus, the porous Bo layers contained a considerable amount of O which was absorbed in the inter-columnar voids and was distributed throughout the film thickness. This O supply permitted the formation of alumina during annealing, and the latter prevented the subsequent diffusion of Al atoms.

G.I.Grigorov, K.G.Grigorov, M.Stoyanova, J.L.Vignes, J.P.Langeron, P.Denjean: Applied Physics A, 1993, 57[2], 195-7

  Table 161

Diffusivity of Al in TiN Films