Pixel Hybridization Technologies for the HL-LHC

During the 2024-2025 shut-down, the Large Hadron Collider (LHC) will be upgraded to reach an instantaneous luminosity up to 7×10³⁴ cm^-2s^-1. This upgrade of the collider is called High-Luminosity LHC (HL-LHC). ATLAS and CMS detectors will be upgraded to meet the new challenges of HL-LHC: an average of 200 pile-up events in every bunch crossing and an integrated luminosity of 3000 fb^-1 over ten years. In particular, the current trackers will be completely replaced. In HL-LHC the trackers should operate under high fluences (up to 1.4 × 10¹⁶ n_eq cm^-2), with a correlated high radiation damage. The pixel detectors, the innermost part of the trackers, needed a completely new design in the readout electronics, sensors and interconnections. A new 65 nm front-end (FE) electronics is being developed by the RD53 collaboration compatible with smaller pixel sizes than the actual ones to cope with the high track densities. Consequently the bump density will increase up to 4 ·10⁴ bumps/cm². Preliminary results of two hybridization technologies study are presented in this paper. In particular, the on-going bump-bonding qualification program at Leonardo-Finmeccanica is discussed, together with alternative hybridization techniques, as the capacitive coupling for HV-CMOS detectors.