Transient enhanced diffusion in preamorphized silicon: the role of the surface

Experiments on the depth dependence of transient enhanced diffusion (TED) of boron during rapid thermal annealing of Ge-preamorphized layers reveal a linear decrease in the diffusion enhancement between the end-of-range (EOR) defect band and the surface. This behavior, which indicates a quasi-steady-state distribution of excess interstitials, emitted from the EOR band and absorbed at the surface, is observed for annealing times as short as 1 s at 900 degrees C, Using an etching procedure we vary the distance x(EOR) from the EOR band to the surface in the range 80-175 nm, and observe how this influences the interstitial supersaturation, s(x), The supersaturations at the EOR band and the surface remain unchanged, while the gradient ds/dx, and thus the flux to the surface, varies inversely with x(EOR). This confirms the validity of earlier modelling of EOR defect evolution in terms of Ostwald ripening, and provides conclusive evidence that the surface is the dominant sink for interstitials during TED. (C) 1999 Elsevier Science B.V. All rights reserved.