Atomic scale evidence of the suppression of boron clustering in implanted silicon by carbon coimplantation

The effect of carbon codoping on boron distribution in implanted silicon has been investigated at the atomic scale using atom probe tomography. Whereas small boron-enriched clusters a few nm in size, containing about 2.4 at. % of boron atoms, are clearly visible in carbon-free B-implanted silicon after annealing at 800°C for 30 min, no boron clustering is evidenced if C is coimplanted in the sample. C coimplantation is known to reduce the electrical deactivation of boron, but, in addition, this suggests that C addition induces a larger fraction of mobile boron near the peak of the B profile.