TRAP-LIMITED INTERSTITIAL DIFFUSION AND ENHANCED BORON CLUSTERING IN SILICON

Boron doped superlattices have been used to detect the diffusion of self-interstitials in Si. Interstitials were generated in the near-surface region by 40 keV Si implantation followed by diffusion at 670-790°C. The interstitial diffusion profile at 670°C is stationary for t≤1 h, demonstrating that the penetration depth of interstitials is limited by trapping. The concentration of traps is estimated to be ∼1017/cm3. For sufficiently long annealing times, interstitials diffuse beyond the trapping length with an effective trap-limited diffusivity ranging from ∼6×10-15 cm2/s at 670°C to ∼1×10-12 cm2/s at 790°C. The high interstitial supersaturation adjacent to the implant damage drives substitutional B into metastable clusters at concentrations below the B solid solubility limit.