It has been shown that the negative bias temperature instability (NBTI) may be significantly suppressed through the incorporation of fluorine in the gate oxide. In this study, we use the electrically-detected magnetic resonance technique of spin dependent recombination and standard gated diode current measurements to investigate the atomic-scale processes involved in fluorine's suppression of NBTI. Our results indicate that fluorine effectively passivates Si/SiO 2 P b0 center defect precursors, but is much less effective at passivating Si/SiO 2 P b1 center defect precursors. Since these two defects have significantly different densities of states, our results maybe useful in modeling NBTI response in fluorinated oxide devices. Our results also help to provide a fundamental explanation for the observation that fluorination has a strong effect on NBTI in "pure" SiO 2 MOS devices, but is ineffective at reducing NBTI in nitrided oxide devices.