Segregation effects of Li, K, and F in Si during depth profiling by oxygen ions

The migration behavior of Li, K, and F during secondary ion mass spectrometry (SIMS) depth profiling was investigated in both n-and p-type Si using different oxygen bombardment conditions. The presence of an electric field across the surface oxide is shown to be the major driving force for both the segregation of Li and K at the SiO₂/Si interface and the antisegregation of F into the oxide. Room temperature SIMS measurements revealed that K segregates at the oxide side of the SiO₂/Si interface, whereas Li segregates at the silicon side of the interface. We have also found that the field-induced segregation of Li and antisegregation of F are less pronounced in high resistivity (11 000-16000 Ωcm) p-type Si than in low resistivity (∼0.011 Ωcm) n-type Si. Although Li segregates at the Si side of the interface in both types of Si, some Li, however, remains at the oxide side in the high resistivity p-type Si. The high solid solubility of Li in amorphous Si is also considered as a driving force for its segregation.