The ForwArd Search ExpeRiment (FASER) is dedicated to search for new particles and physics beyond the Standard Model located 480 m downstream from the ATLAS interaction point at the Large Hadron Collider (LHC). FASER's sub-detectors include the pre-shower, which is a critical component in process of being upgraded into modules of monolithic silicon pixel sensor planes alternated with tungsten absorber planes. As part of this process, a pre-production version chip has been designed in the University of Geneva based on SiGe BiCMOS technology, produced by IHP electronics. The new high-precision pre-shower detector aims to have an increased granularity and sensitivity for light and weakly interacting particles that decay into a pair of photons of energies within a 100 GeV to a few TeV range, and separation ≥200 μm. The pre-production chip has been characterized to evaluate its performance, as well as identify and correct possible defects before the final design of the FASER pre-shower chip.

In this work, results of the characterization of pre-production chip samples both on standard wafer (ρ = 50 Ω⋅cm), and high-resistivity wafer (ρ = 4 kΩ⋅cm) are presented.