A distinguishing property of copper impurities in Si was their very fast diffusivity, which was undesirable in Si device processes. This was the first attempt to simulate the fast diffusion of Cu by first-principles calculations. It was shown that, even near room temperature, the amplitude of Cu vibrations was very large; this was a consequence of the fact that the local mode of Cu has very low frequencies. At T>1000K, the simulations demonstrated clear migration between adjacent cells. The diffusion path was from an interstitial T site to the next T site through an H site. The Arrhenius plot of the calculated diffusion constants agrees with the experimental data on the intrinsic diffusion of Cu, which were currently most reliable data available.

Molecular Dynamics Study of Fast Diffusion of Cu in Silicon. K.Shirai, T.Michikita, H.Katayama-Yoshida: Japanese Journal of Applied Physics, 2005, 44[11], 7760-4