DIFFUSION OF SILICON IN TITANIUM NITRIDE FILMS - EFFICIENCY OF TIN BARRIER LAYERS

Two kinds of reactively evaporated titanium nitride films with columnar (B0 films) and fine-grained film structure (B+ films) have been examined as diffusion barriers, preventing the silicon diffusion in silicon devices. The silicon diffusion profiles have been investigated by 2 MeV He-4+ Rutherford backscattering spectrometry (RBS) after annealing at temperatures up to 900-degrees-C, in view of application of high-temperature processes. The diffusivity from 400 to 900-degrees-C: D (m2 s-1) = 2.5 x 10(-18) exp[-31 kJ/mol/(RT)] in B0 layers and D (m2 s-1) = 3 x 10(-19) exp[-26 kJ/mol/(RT) in B+ TiN layers. The diffusivities determined correspond to grain boundary diffusion, the difference being due to the different microstructure. The very low diffusivity of silicon in B+ TiN layer makes it an excellent high-temperature barrier preventing silicon diffusion.