Results of planar pixel sensor qualification campaign for the CMS Phase 2 upgrade

The Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) at CERN will install a new Inner Tracker (IT) pixel detector for the High-Luminosity upgrade of LHC (HL-LHC). The maximum delivered integrated luminosity expected at the end of the HL-LHC running phase will be 4000\,fb$^{-1}$. At the innermost layer of the IT, a fluence corresponding to a non-ionizing energy loss (NIEL) of $\Phi_{eq}$\,=\,3.5\,$\times$\,10$^{16}$\,cm$^{-2}$ is expected. In this paper, the final design option chosen for planar silicon sensors of the IT will be reviewed. All the layers excluding the innermost of the barrel section of the IT will be equipped with planar n-in-p sensors with an active thickness of 150\,$\mu$m and pixel size of 25\,$\mu$m\,$\times$\,100\,$\mu$m. The sensors used for this characterization campaign were coupled to a demonstrator chip (RD53A) and the modules were irradiated to different fluences up to $\Phi_{eq}$\,=\,2\,$\times$\,10$^{16}$\,cm$^{-2}$ and extensively tested in both CERN and DESY test beam facilities over the last three years. This campaign completed the first step of the vendor qualification and the results obtained are a reference for the next testing phase, based on the final CMS readout chip (CROC). An overview of the results obtained in terms of spatial resolution, hit efficiency, crosstalk, and noise studies is presented. For all the parameters investigated, the results were found to be within the requirements. This made it possible to qualify three vendors and promises excellent performances also for the pre-production phase that will start soon.