Ring-diffusion of gold atoms in silicon

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A new method for brief and high sensitive measurement of concentration profile of low-temperature substitutional gold, expected to diffuse by a ring-mechanism, in silicon has been established by a capacitance measurement on Schottky diodes fabricated on an angle-lapped surface of silicon, with a detection limit less than 10ィイD113ィエD1 cmィイD1-3ィエD1.Annealing characteristics of supersaturated low-temperature substitutional gold in silicon have been investigated by a measurement of concentration profiles of substitutional gold using above method. the concentration decreases uniformly kept intact with a flat profile, and the average concentration decreases rapidly with the annealing time. Diffusion coefficient of the ring-diffusion is obtained as (10ィイD1-5ィエD1-10ィイD1-3ィエD1)exp(-(1.7±0.2)kT) cmィイD12ィエD1/s from the initial concentration dependence of the time constant of the concentration decrease in the annealing. Namely the chemical activation energy for the ring-diffusion of gold in silicon has been obtained as 1.7±0.2 eV.By comparison of concentration profiles of substitutional gold with those of total gold atoms, the rapid decrease of supersaturated low-temperature substitutional gold was made clear to be caused by a homogeneous agglomeration of low-temperature substitutional gold via a ring-diffusion to an agglomeration center, and supersaturated low-temperature substitutional gold agglomerates in the silicon specimen resulting in electrically inactive during the heat-treatment for the annealing.