Near-surface Cu-rich layers were observed by means of the secondary ion mass spectroscopy of intentionally contaminated wafers after thermal oxidation (950C, 2100s). The diffusivity of Cu, at 950C, which was deduced from secondary ion mass spectroscopy profiles was 9 x 10-14. This value was almost 9 orders of magnitude lower than that expected for interstitial diffusants. It was comparable to those of group-III and group-V atoms; which were known to be substitutional diffusants. On the basis of the results, a model was proposed in which the interstitial and substitutional atoms diffused independently, and the slow substitutional diffusion gave rise to a near-surface impurity-rich layer.

Substitutional Diffusion of Transition Metal Impurities in Silicon. L.Zhong, F.Shimura: Japanese Journal of Applied Physics - 2, 1993, 32[8B], L1113-6