  Fully energy-filtered X-ray photoelectron emission microscopy is used to
analyze the spatial distribution of the silicon sub-oxide structure at the
SiO2/Si interface as a function of underlying doping pattern. Using a
spectroscopic pixel-by-pixel curve fitting analysis, we obtain the sub-oxide
binding energy and intensity distributions over the full field of view. Binding
energy maps for each oxidation state are obtained with a spatial resolution of
120 nm. Within the framework of a five-layer model, the experimental data are
used to obtain quantitative maps of the sub-oxide layer thickness and also
their spatial distribution over the p-n junctions. Variations in the sub-oxide
thicknesses are found to be linked to the level and type of doping. The
procedure, which takes into account instrumental artefacts, enables the
quantitative analysis of the full 3D dataset.
