The diffusion of Au in dislocation-free material was investigated at 1473K by using neutron activation analyses and mechanical sectioning. In most wafers, the diffusion profiles were U-shaped, as in the case of previous studies performed at lower temperatures. In these wafers, the Au concentrations in the profile centers, measured after 0.75h diffusion anneals, decreased in inverse proportion to the wafer thickness, in accordance with the so-called kick-out diffusion model. The latter was further confirmed by the good agreement of the contribution from self-interstitials to the self-diffusion coefficient at 1473K, as calculated from the present Au diffusion data using directly measured values of the Si self-diffusion coefficient (table 16). In some Au diffused wafers, W-shaped penetration profiles were found. Using spreading resistance, preferential etching, and X-ray topography studies, it was found that the Au concentration peaks which occurred within these specimens were located at faulted dislocation loops which formed during the in-diffusion of Au. An electron microscopic analysis showed that the stacking faults were of extrinsic type. It was presumed that they were formed by the agglomeration of supersaturated self-interstitials which were produced via the kick-out diffusion mechanism.

U- and W-Shaped Diffusion Profiles of Gold in Silicon. J.Hauber, N.A.Stolwijk, L.Tapfer, H.Mehrer, W.Frank: Journal of Physics C, 1986, 19[29], 5817-36

Table 16

Diffusivity of Au in Si