  The challenging demands of the ATLAS High Luminosity (HL-LHC) Upgrade aim for
a complete swap of new generation sensors that should cope with the ultimate
radiation hardness. FBK has been one of the prime foundries to develop and
fabricate such radiation-hard 3D silicon (Si) sensors. These sensors are chosen
to be deployed into the innermost layer of the ATLAS Inner Tracker (ITk).
Recently, a pre-production batch of 3D Si sensors of 50x50 um2 pixel geometry,
compatible with the full-size ITKPix (RD53B) readout chip, was fabricated. Two
wafers holding temporary metal were diced at IZM, Germany, and a systematic QC
test campaign was carried out at the University of Trento electronics
laboratory. The paper briefly describes the 3D Si sensor design for ATLAS ITk
and the required QC characterization setups. It comprises electrical tests
(i.e., I-V, C-V, and I-T) of non-irradiated RD53B sensors. In addition, the
study of several parametric analyses, i.e., oxide charge density, oxide
thickness, inter-pixel resistance, inter-pixel capacitance, etc., are reported
with the aid of Process Control Monitor (PCM) structures.
