Effect of surface condition on the solid solubility of substitutional gold in the out-diffusion of supersaturated gold in silicon

Gold-diffused silicon specimens are heat-treated at 1000 degreesC or at 700 degreesC for the annealing of supersaturated high-temperature or low-temperature substitutional gold, respectively. The concentration profiles of electrically active gold, namely out-diffusion profiles of supersaturated substitutional gold, are obtained by a capacitance measurement, and those of total gold atoms are measured by SIMS. The concentration of substitutional gold is nearly equal to that of total gold atoms in the annealing of high-temperature substitutional gold, but this is not the case in the annealing of low-temperature substitutional gold. The surface concentration, which is regarded as solid solubility, of high-temperature substitutional gold in silicon bounded by Au-Si fusion is nearly equal to the concentration of the in-diffusion profiles, generally accepted as the solid solubility of gold in silicon. On the other hand, the concentration in the silicon bounded by argon ambiance is about 1/10 of the in-diffusion profiles even at the same temperature, and is about 2 x 10(15) cm(-3) at 1000 degreesC. The reason for the decrease in the surface concentration has not yet been ascertained. The concentration of low-temperature substitutional gold decreases up to a solid solubility, 2 x 10(15) cm(-3) at 700 degreesC, which is much larger than the acceptable solubility, with a flat profile.