The role of F in suppressing B diffusion was investigated by using a buried dopant marker to monitor the interaction of F with interstitials. A B-spike with a peak concentration of 1.2 x 1018/cm3, followed by 500nm of undoped Si, was grown in a low pressure chemical vapor deposition furnace. The wafers were then pre-amorphized and implanted with either B, B and F, BF2, As, As and F, or F, respectively. Following the implants, the samples were rapid thermal annealed at 1050C for very short times (spike). The use of pre-amorphization allows the chemical effect of F to be analyzed independently of implant damage, and the buried layer functions as an indicator of point defect (in this case Si self-interstitial) perturbation. As expected, secondary ion mass spectroscopy showed that the presence of F retards the diffusion of B. In addition, the retained F dose after the rapid thermal annealing was highest in the B-implanted samples. In all samples, the buried layer has diffused by the same amount, indicating that there was no change to the Si self-interstitial population due to F. These results suggested that F has a chemical effect, and retards B diffusion by mainly bonding with B.

Fluorine Interaction with Point Defects, Boron, and Arsenic in Ion-Implanted Si. A.Mokhberi, R.Kasnavi, P.B.Griffin, J.D.Plummer: Applied Physics Letters, 2002, 80[19], 3530-2