Annealing kinetics of the gold-iron complex in silicon

Abstract

Gold and iron are known to interact in silicon at temperatures below ∼400 °C to form gold-iron pairs with band-gap energy levels of Ev +0.434 eV and Ec −0.354 eV. In this work, the details of the formation and dissociation of these pairs were examined and from the equilibrium concentrations a binding energy of 1.22±0.02 eV was deduced. The activation energy of the gold-iron pair formation process was found to be 0.8 eV; when corrections were made to extract the activation energy for the iron diffusion coefficient from the data, a value of 0.42 eV was obtained. This is substantially smaller than the values of 0.7–0.9 eV obtained from iron precipitation and iron-boron pairing studies. It was noted during the higher-temperature dissociation process that there was concurrent precipitation of the iron which caused the dissociation to appear to be a two-stage process. This precipitation also resulted in substantial irreversibility of successive dissociation and pair formation anneals. Finally, it is pointed out that these low-temperature instabilities in the concentration of gold and the deep-level gold-iron complex are likely to result in device instabilities when gold and iron contamination occur.