Aluminium diffusion in titanium nitride films. Efficiency of TiN barrier layers

Two kinds of reactively evaporated titanium nitride films with columnar (B0 films) and fine-grained (B+ films) film structures, respectively, have been examined as diffusion barriers for preventing aluminium diffusion. The aluminium diffusion profiles have been investigated by 2 MeV 4He+ Rutherford backscattering spectrometry (RBS) at temperatures up to 550° C. The diffusivity from 300° C to 550° C is: D[m2s−1]=3×10−18 exp[−30/(RT)] in B0 layers and D[m2s−1]=1.4×10−16 exp[−48/(RT)] in B+ TiN layers. The activation-energy values determined indicate a grain boundary diffusion mechanism. The difference between the diffusion values is determined implicitly by the microstructure of the layers. Thus, the porous B0 layers contain a considerable amount of oxygen absorbed in the intercolumnar voids and distributed throughout the film thickness. As found by AES depth profiling, this oxygen supply allows the formation of Al2O3 during annealing the latter preventing the subsequent diffusion of the aluminium atoms.