Back Side Illuminated SiPM from NIR to NUV light detection

In the last 15 years Fondazione Bruno Kessler (FBK) has developed a custom technology for single-photon avalanche diodes (SPADs) and silicon photomultipliers (SiPMs) optimized for several applications, from high-energy physics experiments to medical imaging or light detection and ranging (LiDAR). In the IPCEI framework, FBK is upgrading its microfabrication facility for the realization of 3D integrated radiation sensors. In the specific case of SiPMs, 3D integration technologies will allow to improve its capabilities by using back side illuminated (BSI) devices and Through Silicon Vias (TSV) interconnections. The BSI approach for SiPMs can be exploited to improve the current photon detection efficiency (PDE), even in the wavelength ranges far away from the visible spectrum, where typically it drops down to about 10% for the near infrared (NIR) and about 15% for vacuum ultraviolet (VUV). A first batch of BSI SiPMs for NIR detection was recently fabricated at FBK as a proof of concept. After wafer bonding and thinning, the characterization results showed an increase of the PDE of about 50% at 900 nm for BSI sensors with metal reflectors compared with the standard front side illuminated (FSI) technology. Research on the realization of the fabrication process modules optimized for near ultraviolet (NUV) and VUV BSI SiPMs is currently ongoing and will also be presented and discussed.