Microscopic defects in silicon induced by zinc out-diffusion

We have performed Zn out-diffusion experiments in homogeneously Zn-doped Si in the temperature range from 850 to 1207 degrees C. Diffusion profiles of Zn measured by spreading-resistance profiling are accurately described on the basis of the simultaneous occurrence of the kick-out and the dissociati ve diffusion mechanisms. Compared to Zn in-diffusion, Zn out-diffusion tend s to be dominated by the dissociative mechanism, i.e. preferentially in reg ions of high Zn concentration. Numerical modeling of the out-diffusion prof iles yields fairly reliable data for the vacancy transport coefficient (CvD v)-D-eq. In contrast, an accurate determination of the vacancy equilibrium concentrations C-v(eq) presumably suffers from vacancy agglomerates whose f ormation is driven by the vacancy supersaturation arising from the dissocia tive out-diffusion of Zn. Microscopic defects decorated with Cu3Si have bee n detected after the out-diffusion process by preferential etching and tran smission electron microscope analysis. A tentative explanation for the obse rved Cu3Si precipitates invokes their nucleation on vacancy clusters. (C) 2 000 Elsevier Science S.A. All rights reserved.