THE ROLE OF EXTENDED DEFECTS ON TRANSIENT BORON-DIFFUSION IN ION-IMPLANTED SILICON

Transient tail diffusion of boron in Si(100) has been investigated as a function of boron implant condition, dose, energy, time, temperature and silicon or germanium post-implantations at doses above and below the amorphization threshold. Boron was implanted at energies in the range 5-380 keV and at doses in the range 2 x 10(12) to 5 x 10(15) cm-2 either along [100] or in a random direction. Significantly longer transient boron tail diffusion is observed for implants along [100]. These results reflect the differences between the random and channeling implants in the position of the damage distribution relative to the boron profile. Post-implantation with 1 MeV Si-29 ions below the amorphization threshold can reduce boron tail diffusion if the silicon dose is high enough (5 x 10(13) cm-2 or greater) to form extended defects during the anneal. Lower silicon doses do not influence boron diffusion. Annealing of extended defects also results in anomalous diffusion. These results demonstrate that silicon interstitials cause the enhanced boron diffusion. Amorphization of boron-implanted silicon with Si-29 or Ge-73 ions prevents transient boron tail diffusion during subsequent annealing if the boron profile is completely incorporated in the amorphized region.