Reactively evaporated films with columnar or fine-grained structures were investigated for use as diffusion barriers to Si. After annealing at temperatures of up to 900C, the profiles of diffused Si were investigated by using 2MeV 4He+ Rutherford back-scattering spectrometric techniques. It was found that the diffusion data for columnar-grained films, at temperatures of between 400 and 900C, could be described by:

D (m2/s) = 2.5 x 10-18 exp[-31(kJ/mol)/RT]

The diffusion data for fine-grained films, at temperatures of between 400 and 900C, could be described by:

D (m2/s) = 3 x 10-19 exp[-26(kJ/mol)/RT]

It was concluded that these values represented grain boundary diffusivities, and that the differences between the 2 materials were caused by the grain structure.

K.G.Grigorov, G.I.Grigorov, M.Stoyanova, J.L.Vignes, J.P.Langeron, P.Denjean, J.Perriere: Applied Physics A, 1992, 55[5], 502-4