Segregation under low-energy oxygen bombardment in the near-surface region

We found that a transient region of SIMS profiles was suppressed to less than the native oxide in silicon, with O2+ bombardment energy of less than 0.2 keV under an incident angle of 0° with respect to the surface normal without oxygen flooding. However, gallium segregated significantly due to oxidation caused by O2+ bombardment in this condition. We also found that the segregation decreased as the incident angle increased, and that it disappeared at the angle of around 40°, which was verified by comparing SIMS profiles with the HR-RBS profile. These results suggested that the angle of around 40° was the critical angle to prevent segregation. The transient region was almost the same at angles of 0–40°. Therefore, we consider that the energy of 0.2 keV at the angle of around 40° under O2+ bombardment without oxygen flooding is the optimum SIMS condition for depth profiling in the near-surface region. On the other hand, the profile shift of arsenic depending on the angle was quite different as compared with gallium, but the shift was a minimum at the same critical angle. We expect that more accurate profiles for other impurities can be obtained using this SIMS condition.