The migration of Pt was investigated by using spreading resistance techniques, and substrates with various dislocation densities. The results for essentially perfect non-dislocated material provided evidence for the kick-out mechanism, due to the appearance of characteristic features in the concentration-depth profiles and to the diffusion-induced formation of stacking faults. In the case of solar-grade Si, the incorporation of substitutional Pt into the bulk was governed by the annihilation of self-interstitials at grown-in dislocations with a density of about 109/m2. In this material, the efficiency of dislocations as self-interstitial sinks appeared to be reduced and to depend upon the penetration depth. Measurements of plastically deformed material with a dislocation density of 1011 to 1013/m2 yielded, for the first time, diffusion profiles that were governed by the transport properties of interstitial Pt. The temperature dependence of the overall Pt diffusivity (table 75) could be described by:

D(m2/s) = 0.00021 exp[-1.79(eV)/kT]

W.Lerch, N.A.Stolwijk, H.Mehrer, C.Poisson: Semiconductor Science and Technology, 1995, 10[9], 1257-63

Table 75

Diffusivity of Pt in Si