Au agglomerates observed in the out-diffusion process of supersaturated high-temperature substitutional Au in Si

Abstract

Out-diffusion profiles of supersaturated substitutional Au in Si annealed at 900 °C for 90 h have been measured by SIMS and ICTS methods over a distance of 80 μm from the specimen surface. The tendency of the profile of total Au atoms measured by SIMS and that of electrically active substitutional Au measured by ICTS agrees well, but the very small regions containing high-concentration of Au atoms, 3 × 10²² cm⁻³, are observed sporadically at the distance deeper than 10 μm from the surface by SIMS method. The size of the high-concentration region is estimated to be about 20 nm and its density is about 2 × 10¹⁰ cm⁻³. The small agglomerates contain 10⁵–10⁷ Au atoms and many of them contain about 2 × 10⁵ atoms. The observed agglomerate is a new agglomeration of Au in Si. The state of the agglomeration (namely, precipitates of Au, agglomeration of substitutional Au in Si, or a new state) is not clear by SIMS measurement.