Beam Test Results of Thin n-in-p 3D and Planar Pixel Sensors for the High Luminosity LHC Tracker Upgrade at CMS

This paper describes the development of new 3D and planar silicon pixel sensors designed for the Compact Muon Solenoid (CMS) Phase-2 Upgrade at High Luminosity LHC (HL-LHC). The project is funded by INFN and sensors are produced in collaboration with the FBK foundry. The HL-LHC will operate at an instantaneous luminosity approximately 5 times larger than the original LHC design, significantly increasing the number of concurrent collisions per bunch crossing, the integrated luminosity delivered to the experiments and, as a consequence, the radiation dose that the detectors will have to sustain. In order to cope with these future conditions, upgrades to the detectors are required. This is necessary for the pixel tracker that is the closest to the interaction point and will be replaced. In this paper, the results, from beam tests performed at Fermilab Test Beam Facility, of thin (100 $\mu$m and 130 $\mu$m thick) n-in-p type sensors, assembled into hybrid single chip modules bump bonded to the PSI46dig readout chip, will be presented. A comparison of the performances obtained with planar sensors before and after proton irradiation up to $3\times10^{15}$ n$_{eq}$/cm$^2$ will be also discussed. The paper will also report the results obtained with the first 3D pixel sensors 130 $\mu$m thick with columnar electrodes for different pixel cell prototypes. The novelty of the 3D prototypes is their small pixel cell size, ranging form the standard $100$~$\mu$m~$\times$~$150$~$\mu$m, down to $50$~$\mu$m~$\times$~$50$~$\mu$m and $25$~$\mu$m~$\times$~$100$~$\mu$m, which are the preferred dimensions in the high pile-up environment of the HL-LHC.