Thin n-in-p pixel sensors and the SLID-ICV vertical integration technology for the ATLAS upgrade at the HL-LHC

This R&D activity is focused on the development of new modules for the upgrade of the ATLAS pixel system at the High Luminosity LHC (HL-LHC). The performance after irradiation of n-in-p pixel sensors of different active thicknesses is studied, together with an investigation of a novel interconnection technique offered by the Fraunhofer Institute EMFT in Munich, the Solid–Liquid-InterDiffusion (SLID), which is an alternative to the standard solder bump-bonding. The pixel modules are based on thin n-in-p sensors, with an active thickness of 75μm or 150μm, produced at the MPI Semiconductor Laboratory (MPI HLL) and on 100μm thick sensors with active edges, fabricated at VTT, Finland. Hit efficiencies are derived from beam test data for thin devices irradiated up to a fluence of 4×1015neq/cm2. For the active edge devices, the charge collection properties of the edge pixels before irradiation are discussed in detail, with respect to the inner ones, using measurements with radioactive sources. Beyond the active edge sensors, an additional ingredient needed to design four side buttable modules is the possibility of moving the wire bonding area from the chip surface facing the sensor to the backside, avoiding the implementation of the cantilever extruding beyond the sensor area. The feasibility of this process is under investigation with the FE-I3 SLID modules, where Inter Chip Vias are etched, employing an EMFT technology, with a cross section of 3μm×10μm, at the positions of the original wire bonding pads.