Surface roughening effect in sub-keV SIMS depth profiling

Low energy secondary ion mass spectrometry (SIMS) is used for the purpose of achieving high depth resolution and reducing the surface transient. However, profiling using sub-keV primary ion energies is complicated by the early onset of surface roughening. A Cameca IMS 6f SIMS instrument is used to study the development of surface roughness in the sub-keV primary ion energy regime using B and SiGe delta doped Si standard samples. Energy dependent analyses using 0.5–2.0 keV O2+ show that while higher depth resolution is achievable at 0.5 keV, the onset of roughening occurs earlier. The onset of surface roughness is also shown to occur earlier for smaller incidence angles (in the 46–69° range) using 0.5 keV primary ion energy. This angular dependence is explained using the heterogeneity layer model.