Room temperature migration of boron in crystalline silicon during secondary ion mass spectrometry profiling

Abstract

Recently we have demonstrated that substitutional boron in crystalline silicon can migrate for long distances even at room temperature (RT) and below during secondary ion mass spectrometry (SIMS) profiling. The phenomenon is suppressed after amorphization or by cooling the sample. The above data force to reconsider the observations obtained in the last decades by SIMS in light of possible long-range migration artifacts. Here we show that the use of oxygen flooding (OF) during the analysis enhances the injection of self-interstitials (I) responsible for the migration of B, producing profiles that are more broadened and less accurate than in ultrahigh vacuum. On the other hand, by properly controlling OF, we have obtained new insights on the mechanisms of B diffusion and interaction with intrinsic traps at RT. Moreover, by cooling the sample the migration of B is suppressed even while using OF, allowing measurements of boron deltas in c-Si of unprecedented level of accuracy and sensitivity. Finally, we have clarified the role of the migration phenomena on the profiling of ultra low energy B implants for ultra shallow junctions.