Electrical characterization of copper related defect reactions in silicon

Defect reactions involving interstitial copper impurities (Cui) in silicon are reviewed. The influence of the Coulomb interaction between positively charged copper and negatively charged defects, such as acceptor states of transition metals and lattice defects, on the complex formation rate is discussed in detail. The diffusivity of interstitial copper and the dissociation kinetics of copper–acceptor pairs are studied using the recently introduced transient ion drift (TID) method. TID results reveal that most interstitial copper impurities remain dissolved immediately after the quench and form pairs with shallow acceptors. It is shown that in moderately and heavily doped silicon the diffusivity of copper is trap limited, while in low B-doped silicon the interstitial copper–acceptor pairing is weak enough to allow the assessment of the copper intrinsic diffusion coefficient. The intrinsic diffusion barrier is estimated to be 0.18±0.01 eV. It is concluded that the Coulomb potential used in previous publications underestimated considerably the acceptor–copper interaction. In light of these results, a general discussion on Cu related defect reactions is given.