  We report on the experimental study made on a successive prototype of
High-Voltage CMOS (HV-CMOS) ATLASPix2 sensor for the tracking detector
application, developed with 180 nm feature size. These sensors are to qualify
mainly the peripheral data processing blocks (e.g. Command Decoder, Trigger
Buffer, etc.). It is a smaller version of 24 X 36 pixelated sensor in
comparison to the earlier generation of ATLASPix1 fabricated in both ams AG,
Austria, and TSI Semiconductors, USA. While ams produced ATLASPix2 showed
breakdown voltage 50 V in nonirradiated condition as it was seen on its
predecessors ATLASpix1, TSI produced prototypes reported breakdown voltage
greater than 100 V. The chosen wafer of MCz 20 Ohm.cm P-type substrate
resistivity can deplete a few tenths of um, where the process-driven surface
damage can have a greater impact on device operating conditions before and
after irradiation. In an aim to understand device intrinsic performance at the
irradiated case, a dedicated neutron irradiation campaign has been made at JSI
for different fluences. Characterizations have been performed at different
temperatures after irradiation to analyze the leakage current and breakdown
voltage before and after irradiation. TSI prototypes showed a breakdown voltage
decrease 90 V due to impact ionization and enhanced effective doping
concentration. Results demonstrated for the neutron-irradiated devices up to
the fluence of 2 X 10^15 neq/cm2 can still safely be operated at a voltage high
enough to allow for high efficiency. Accelerated Annealing steps also made on
selective irradiated ATLASPix2 samples, equivalent to more than two years of
room-temperature annealing (at 20 degC), and they showed the reassuring
expected breakdown voltage increase and damage constant rate alpha^* (geometry
dependent) decrease, driven by the beneficial annealing.
