PERFORMANCE OF TXRF and GI-XRF ANALYSES - Total-Reflection X-Ray Fluorescence Analysis and Related Methods - page 263

Figure4.24. Flow chart for depth profiling by wet-chemical etching and TXRF analysis. Several
steps have to be done and the loop has to be repeated for a lot of sublayers. The second weighing
may be redundant if care is taken for an extremely clean working. Finally, two depth profiles can be
plotted: one determined for the freshly etched surfaces, the other for the etching solutions. Figure
from Ref. [72], reproduced with permission. Copyright1999 by Elsevier.
the oxide layer (2.27 g/cm 3 ) and the area of the wafer piece, the thickness of the
respective sublayer can be calculated. The next step is TXRF analysis of the
implanted ions (1) within the etching solution and (2) at the freshly etched
surface of the sample. These measurements are carried out with an energy-
dispersive Si(Li) or a Si drift detector of a TXRF spectrometer. For that
purpose, (1) a small droplet (10 μ l) of the etching solution is pipetted onto a
clean Plexiglas carrier and analyzed by the detector and (2) a small area of the
freshly etched surface (about 0.5 cm 2 ) is analyzed. The glancing angle is chosen
to be below the critical angle of total reflection and the intensity ratio of the net
counts N ion / N Si is measured in a counting time of 100 s with an RSD of 2-3%.
It leads to the mass ratio of implanted ions and atoms of the substrate,
which is determined quantitatively by sensitivity factors after calibration.