Effect of fluorine on the diffusion of boron in ion implanted Si

Ion implants of 1 keV B-11(+) and 5 keV BF2+, to a dose of 1 x 10(15)/cm(2) at a tilt angle of 0 degrees, were implanted into preamorphized (Si+, 70 k eV, 1 x 10(15)/cm(2)) wafers. These samples were rapid thermal annealed in an ambient of 33 ppm of oxygen in N-2 at very short times (<0.1 s spike ann eals) at 1000 and 1050 degrees C to investigate the effects of the fluorine in BF2 implants on transient enhanced diffusion (TED). By using a relative ly deep preamorphization of 1450 Angstrom, any difference in damage between the typically amorphizing BF2 implants and the nonamorphizing B implants i s eliminated because the entire profile (<800 Angstrom after annealing) is well contained within the amorphous layer. Upon annealing, the backflow of interstitials from the end-of-range damage from the preamorphization implan t produces TED of the B in the regrown layer. This allows the chemical effe ct of the fluorine on the TED of the B in the regrown Si to be studied inde pendent of the damage. The secondary ion mass spectroscopy results show tha t upon annealing, the presence of fluorine reduces the amount of B diffusio n by 30% for the 1000 degrees C spike anneal, and by 44% for the 1050 degre es C spike anneal. This clearly illustrates there is a dramatic effect of F on TED of B independent of the effects of implant damage. Analysis of the temperature dependence of the enhancement factors point to transient enhanc ed diffusion not boridation as the source of the interstitials. (C) 1998 Am erican Institute of Physics. [S0003-6951(98)03035-6].