Abstract
The segregation and pile-up of arsenic atoms at the Si/SiO2 interface in steady state was
investigated in detail by a combination of gracing incidence x-ray fluorescence spectroscopy
GI-XRF measurements, electrical measurements, etching on the nanometer scale, and
measurements of the step heights by interferometry. Using GI-XRF measurements and removal of
the highly doped segregation layer by a sensitive etching process it was possible to distinguish
clearly between the piled-up atoms and the arsenic atoms in the bulk over a large range of
implantation doses, from 31012 to 11016 cm−2. The samples were annealed at different
temperatures from 900 °C to 1200 °C for time periods long enough to make sure that the
segregation reflects an equilibrium state. With additional step height measurements at line-space
structures, the thickness of the layer with the piled-up arsenic and the shape of the segregation
profile was determined. Electrical measurements indicated that the segregated arsenic atoms are
deep donors with an electrical activity that increases eventually to full electrical activation for high
sheet concentrations of the segregated atoms. The measured data can be modeled as a steady state
of neutral arsenic atoms in the segregation layer with positively charged substitutional arsenic atoms
and free electrons. For the highest concentration, a saturation of the sheet concentration of
segregated arsenic atoms was observed that correlates with the increase in electrical activation. For
the use in process simulation programs, a three-phase segregation model was adapted and
calibrated.