  The radiation hardness of passive CMOS pixel sensors fabricated in 150 nm
LFoundry technology is investigated. CMOS process lines are especially of
interest for large-scale silicon detectors as they offer high production
throughput at comparatively low cost. Moreover, several features like
poly-silicon resistors, MIM-capacitors and several metal layers are available
which can help enhance the sensor design. The performance of a 100
$\mathrm{\mu}$m thin passive CMOS sensor with a pixel pitch of 50
$\mathrm{\mu}$m at different irradiation levels, 5 $\times$
10$^{15}$n$_{\mathrm{eq}}$cm$^{-2}$ and 1 $\times$
10$^{16}$n$_{\mathrm{eq}}$cm$^{-2}$, is presented. The sensor was bump-bonded
and read out using the RD53A readout chip. After the highest fluence a
hit-detection efficiency larger than 99% is measured for minimum ionising
particles. The measured equivalent noise charge is comparable to conventional
planar pixel sensors. Passive CMOS sensors are thus an attractive option for
silicon detectors operating in radiation harsh environments like the upgrades
for the LHC experiments.
