Evaluation of Planar Silicon Pixel Sensors with the RD53A Readout Chip for the Phase-2 Upgrade of the CMS Inner Tracker

The Large Hadron Collider at CERN will undergo an upgrade in order to increase its luminosity to 7.5 x 1034 cm-2s-1. The increased luminosity during this High-Luminosity running phase, starting around 2029, means a higher rate of proton-proton interactions, hence a larger ionizing dose and particle fluence for the detectors. The current tracking system of the CMS experiment will be fully replaced in order to cope with the new operating conditions. Prototype planar pixel sensors for the CMS Inner Tracker with square 50 gm x 50 gm and rectangular 100 gm x 25 gm pixels read out by the RD53A chip were characterized in the lab and at the DESY-II testbeam facility in order to identify designs that meet the requirements of CMS during the High-Luminosity running phase. A spatial resolution of approximately 3.4 gm (2 gm) is obtained using the modules with 50 gm x 50 gm (100 gm x 25 gm) pixels at the optimal angle of incidence before irradiation. After irradiation to a 1 MeV neutron equivalent fluence of (Deq = 5.3 x 1015 cm-2, a resolution of 9.4 gm is achieved at a bias voltage of 800 V using a module with 50 gm x 50 gm pixel size. All modules retain a hit efficiency in excess of 99% after irradiation to fluences up to 2.1 x 1016 cm-2. Further studies of the electrical properties of the modules, especially crosstalk, are also presented in this paper.