Characterization of the pile-up of As at the SiO2/Si interface

The pile up of As at the SiO2/Si interface was investigated by grazing incidence X-ray fluorescence spectroscopy in combination with removal of silicon layers by etching with thicknesses on the order of a nanometer. In order to determine the thickness of the silicon layers removed at the interface, atomic force microscope measurements were performed at trench structures. With this method, it is possible to determine the thickness of the piled-up region in the silicon. In addition, it is possible to clearly distinguish between the segregated atoms and the As atoms in the bulk over a large range of implantation doses from 3middot1012 cm-2 to 1middot10-16 cm-2. The samples were annealed at 900degC and 1000degC, respectively, for times sufficiently long to ensure that the segregation reflects an equilibrium effect. With this approach, the pile-up of As was measured with new precision.