Radiation Hardness of Digital Pixel Sensor Prototypes in 65 nm CMOS Technology for the ALICE ITS3 Upgrade

The ALICE Inner Tracking System will be upgraded to its third version (ITS3) in the LHC Long Shutdown 3 (2026-2028). The ITS Inner Barrel will be replaced by a truly cylindrical detector consisting of six half-layers from stitched wafer-scale monolithic active pixel sensors (MAPS). The sensor chip will produced in the TPSCo. 65 nm CMOS technology. In a first submission in this technology, several different test structures were produced. One of them is the Digital Pixel Test Structure (DPTS), which features 1024 pixel with a digital readout. In order to evaluate the radiation hardness of this test structure, irradiation campaigns with X-rays as well as with neutrons were carried out. Results from these studies demonstrate sufficient radiation hardness of these structures to ionizing doses of 10 kGy and non-ionizing doses of 1e13 1 MeV neq cm−2 as required for the ITS3. Moreover, this technology is candidate for the potentially upcoming ALICE 3 upgrade, where much higher radiation doses are expected. First results indicate that a sufficient ionizing radiation hardness is realistic in this technology. The non-ionizing radiation hardness is not sufficiently demonstrated yet. However, previous studies focused mainly on the operation at room temperature whereas sub-zero cooling is a viable option for ALICE 3.