The effect of Sn upon the structural evolution of Al films was analyzed in detail. The films were prepared in HV by magnetron sputtering at a 180C substrate temperature on Si wafers covered by the native oxide. The Al and Sn were sequentially sputtered from a 100mm diameter direct-current magnetron target. The samples consisted of an Al base-layer (400nm), a Sn interlayer (10nm) and an Al-capping layer (400nm) and were investigated by analytical and high resolution X-TEM, AFM and scanning Auger electron spectroscopy. If the Sn-interlayer was oxidized, no effect on the growth of the Al-capping layer was observable. If, on the other hand, the Sn-interlayer was prevented from oxidation grain growth was promoted in the Al-capping layer as confirmed by X-TEM and AFM. The capping layer contained intragranular line-like features roughly parallel to the substrate plane. Microanalysis revealed the presence of Sn in the capping layer and indicated that Sn was associated with these linear features. The promotion of grain growth in the capping layer could be attributed to the permanent transport of Sn to the growth front via grain boundaries; as was confirmed by dynamic scanning Auger electron spectroscopic measurements. The linear intragranular feature formation was explained by the oxidation of Sn on the free surface due to the residual O present in the background gas.

Solid-State Diffusion of Sn in Polycrystalline Al Films. C.Eisenmenger-Sittner, H.Bangert, C.Tomastik, P.B.Barna, A.Kovács, F.Misiak: Thin Solid Films, 2003, 433[1-2], 97-102