Sputter-Induced Segregation of As in Si During SIMS Depth Profiling

The analysis of very abrupt profiles with SIMS is limited by sputter-induced redistribution processes such as collisional mixing [1–4] and radiation-enhanced diffusion [5,6]. The enhancement of the ionisation yield for a silicon substrate subject to normal incidence oxygen bombardment, or to oxygen flooding, leads to the formation of a silicon dioxide layer at the surface [7]. The presence of this oxide leads to another profile redistribution mechanism i.e. a chemically enhanced directional diffusion or segregation [8]. In a previous investigation, the redistribution of As in Si, under oxygen bombardment, was monitored by grazing exit RBS; unusually large decay lengths were observed for samples sputtered with 1700eV O 2 + in a reactive ion etcher (6). In this paper we present further analysis and develop a model to explain these observations.