Fabrication technologies of back-side illuminated SiPM for VUV/NUV light detection at Fondazione Bruno Kessler

Abstract The development of Front-Side Illuminated (FSI) Silicon Photomultipliers (SiPMs) has significantly advanced over the past years, with improvements in the fill factor (FF) and photon detection efficiency (PDE). However, further improvements are not straightforward without a deep modification in the internal structure of the microcell. A new approach based on the back-side Illuminated (BSI) SiPMs concept has been proposed to overcome these limitations, offering the potential for 100% FF, even with small microcell sizes. This paper focuses on the fabrication challenges associated with BSI SiPMs, particularly optimized for Vacuum Ultraviolet (VUV) and Near Ultraviolet (NUV) light detection, where high efficiency requires the complete removal of the substrate and the creation of a thin active “entrance window” for an efficient collection of the photogenerated carriers.