Microscopic defects in silicon induced by zinc out-diffusion

Abstract

We have performed Zn out-diffusion experiments in homogeneously Zn-doped Si in the temperature range from 850 to 1207°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 dissociative diffusion mechanisms. Compared to Zn in-diffusion, Zn out-diffusion tends to be dominated by the dissociative mechanism, i.e. preferentially in regions of high Zn concentration. Numerical modeling of the out-diffusion profiles yields fairly reliable data for the vacancy transport coefficient CVeqDV. In contrast, an accurate determination of the vacancy equilibrium concentrations CVeq presumably suffers from vacancy agglomerates whose formation is driven by the vacancy supersaturation arising from the dissociative out-diffusion of Zn. Microscopic defects decorated with Cu3Si have been detected after the out-diffusion process by preferential etching and transmission electron microscope analysis. A tentative explanation for the observed Cu3Si precipitates invokes their nucleation on vacancy clusters.