Out-Diffusion and Precipitation of Copper in Silicon: An Electrostatic Model

Concentrations of mobile interstitial copper and precipitated copper in silicon were studied after a high temperature intentional contamination and quench to room temperature. It was found that below a critical contamination the copper predominantly diffuses out to the surface, while for higher initial copper concentrations it mainly precipitates in the bulk. The critical copper contamination equals the acceptor concentration plus ${10}^{16}\mathrm{cm}{}^{-3\mathrm{}}$. This behavior can be explained by the electrostatic interaction between the positively charged interstitial copper and the forming copper precipitates.