REDUCTION OF TRANSIENT BORON-DIFFUSION IN PREAMORPHIZED SI BY CARBON IMPLANTATION

Boron diffusion in preamorphized Si is studied as a function of dose of carbon ion implantation. The boron was implanted at 20 keV with a dose of 1 X 10(15) cm-2, and carbon was implanted at 60-90 keV. The preamorphized depth was 230 nm. It is shown that transient enhanced diffusion occurs even in the preamorphized region without C+ implantation. The diffusion constant is larger than the standard one by about one order of magnitude in the case of 1000-degrees-C annealing for 15 s. This enhancement is eliminated by C+ implantation at a dose of about 10(15) cm-2. This implantation also reduces the defects at the amorphous/crystal interface. These findings indicate that the implanted carbon acts as a sink of excess interstitials.