The role of fluorine in suppressing boron diffusion was investigated by utilizing a buried dopant marker to monitor the interaction of fluorine with interstitials. A boron spike with a peak concentration of 1.2×1018 cm−3 followed by 500 nm of undoped silicon was grown in a low pressure chemical vapor deposition furnace. The wafers were then preamorphized 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 (RTA) at 1050 °C for very short times (spike). The use of preamorphization allows the chemical effect of fluorine 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 shows that the presence of fluorine retards the diffusion of boron. In addition, the retained fluorine dose after the RTA is highest in the boron-implanted samples. In all samples the buried layer has diffused by the same amount, indicating that there is no change to the silicon self-interstitial population due to fluorine. These results suggest that fluorine has a chemical effect, and retards boron diffusion by mainly bonding with boron. © 2002 American Institute of Physics.