Copper passivation of boron in silicon and boron reactivation kinetics

Copper passivation of substitutional boron in single-crystal silicon and the reactivation kinetics of the passivated boron have been investigated with the use of Schottky-barrier structures formed by the deposition of copper on boron-doped silicon at room temperature. It is found that passivation of the boron acceptors occurs after copper deposition. The results suggest that the fast-diffusing interstitial ${\mathrm{Cu}}^{+}$ passivates the boron acceptors by forming neutral B-Cu complexes, rather than by direct compensation. No compensating donor levels associated with Cu are observed. These results are consistent with recent theoretical predictions. The reactivation kinetics are first order with an activation energy of 0.89 eV, and the annealing process is found to be controlled by long-range diffusion, rather than by pure dissociation. The thermal dissociation of the B-Cu complexes is driven by the formation of the copper silicide η’-${\mathrm{Cu}}_3$Si, indicating the importance of silicide formation in the reactivation of the boron acceptors.