Zero-energy SIMS depth profiling: The role of surface roughness development with XeF2-based etching

To obtain monolayer depth resolution in the zero-energy SIMS concept, an almost atomically flat surface during the electron beam-induced etching (EBIE) is crucial. However, the surface roughness observed with Si EBIE and XeF2 shows the same characteristics as observed during spontaneous etching of Si with XeF2. The subsurface fluorine concentration in a Si EBIE process (even in amass transport limited regime) can influence the unactivated formation of the SiFx reaction layer as well, and therefore, contribute to observed roughness development. SiO2 EBIE leads to extreme pit formation due to preferential etching of Si at the SiO2/Si interface. In general, preferential etching can deteriorate or enhance the depth resolution as shown on a SiGe epilayer structure. Finally, the capabilities of zero-energy SIMS are shown on an ultra-shallow SiGe structure demonstrating a narrow surface transient and a very good depth resolution in the surface region. Copyright (C) 2010 John Wiley & Sons, Ltd.