Annealing of low-temperature substitutional gold in silicon: Ring-diffusion of substitutional gold in silicon

Annealing characteristics of low-temperature substitutional gold in silicon have been investigated by a special annealing method. Concentration profiles of substitutional gold and their decrease during the annealing were measured with an isothermal capacitance transient spectroscopy, ICTS, and resistivity. The concentration decreases uniformly kept intact with a flat profile and the average concentration decreases rapidly with the annealing time. The rapid decrease is caused by a homogeneous agglomeration of low-temperature substitutional gold via a ring-diffusion to an agglomeration center. Diffusion coefficient of the ring-diffusion was obtained as (10(-5)-10(-3))exp(-(1.7+/-0.2)/kT) cm(2)/s from the initial concentration dependence of the time constant in the annealing. A tendency of out-diffusion profile near the specimen surface was observed, however, the observed diffusion length was larger than the length calculated from the diffusion coefficient. The average concentration obtained from resistivities is followed by a slow decreases after the first rapid one. The slow decrease may be caused by a diffusion of other impurities such as shallow or deep accepters.