Diffusion and transient trapping of metals in silicon

In this study, the transport of ion-implanted metals to cavities and subsequent metal dissolution have been examined for short- and long-annealing times using Rutherford backscattering and channeling, transmission electron microscopy, and neutron activation analysis. A band of nanocavities in Si is found to be a very efficient sink for implanted Au and Cu during short-time annealing. In this case, the system appears to be in pseudoequilibrium where the fraction of soluble metals is well below the expected solubility even when bulk phase (silicide) is present. However, long-term annealing results in dissolution of metals and progression towards thermal equilibrium solubilities. We suggest that the slow equilibration is a result of both the local metal supersaturation and disorder resulting from implantation. The role of defects (particularly Si interstitials) in both the transient and slow equilibration processes is discussed. For example, metal transport and trapping at cavities are defect mediated processes and subsequent dissolution can also be defect limited.