Investigation of copper precipitation in denuded zone in Czochralski silicon

The precipitation behavior of copper in denuded zone (DZ) of Czochralski silicon has been systematically investigated by means of etching and optical microscopy (OM). Firstly, the samples were treated in a conventional furnace by high-low-high annealing for the formation of denuded zone. Subsequently, copper contamination was introduced at different temperatures. Finally, samples were treated with rapid thermal annealing (RTA) and conventional furnace annealing separately. It was found that, copper precipitates could be observed in DZ through OM only in the samples which experienced RTA followed by contamination in 900 ℃ and 1100 ℃. This indicates that the out-diffusion of vacancy which is produced in the process of RTA is the main cause for the copper precipitation in DZ.