The INFN R&D: New Pixel Detector for the High Luminosity Upgrade of the LHC

The High Luminosity upgrade of the CERN-LHC (HL-LHC) demands for a new high-radiation tolerant solid-state pixel sensor capable of surviving fluencies up to a few $10^{16}$~ particles/cm$^2$ at $\sim$3~cm from the interaction point. To this extent the INFN ATLAS-CMS joint research activity, in collaboration with Fondazione Bruno Kessler-FBK, is aiming at the development of thin n-in-p type pixel sensors for the HL-LHC. The R\&D covers both planar and single-sided 3D columnar pixel devices made with the Si-Si Direct Wafer Bonding technique, which allows for the production of sensors with 100~$\mu {\rm m}$ and 130~$\mu {\rm m}$ active thickness for planar sensors, and 130~$\mu {\rm m}$ for 3D sensors, the thinnest ones ever produced so far. First prototypes of hybrid modules bump-bonded to the present CMS and ATLAS readout chips have been tested in beam tests. Preliminary results on their performance before and after irradiation are presented.