Silicon photomultipliers (SiPMs) are becoming the detector of choice in many fields, including medical instrumentation, industry and scientific experiments. The sensitivity of SiPMs typically covers the entire visible range but, in some applications, sensitivity in the vacuum ultraviolet (VUV) or near infrared (NIR) range is required, posing significant challenges in the technology development and in the device design. Fondazione Bruno Kessler (FBK) is now involved in research programs and instrumental upgrades towards the realization of backside illuminated (BSI) SiPMs. A first demonstration of BSI SiPMs has been recently obtained. A batch of SiPM wafers was thinned to a final thickness of about 10 μm, a few microns in excess compared to the nominal epitaxial layer thickness. An anti-reflective coating was built on the backside and a glass carrier wafer was permanently bonded in order to provide mechanical stability. Although this was a preliminary attempt, mainly intended as a process demonstration, this batch of thinned substrate SiPMs provided an increased photon detection efficiency (PDE) in the NIR range when operated in BSI configuration. The increase in the PDE was of about 50% at 900 nm in devices with metal reflectors, compared to the same front side illuminated technology. Further developments are in progress at FBK towards a BSI SiPM technology optimized for VUV light detection. In several frontier physics experiments, the direct detection of scintillation light produced by liquid noble elements is needed, ranging from 80 nm (He and Ne) to 178 nm (Xe). A BSI SiPM approach could bring several advantages in these fields, such as more flexibility in the entrance window fabrication and the potential of exploiting 3D-integration strategies.
Developments Towards Backside Illuminated Silicon Photomultipliers at Fondazione Bruno Kessler
Alberto Mazzi
;Giovanni Paternoster;Alberto G. Gola;Fabio Acerbi;Pierluigi Bellutti;Giacomo Borghi;Lorenza Ferrario;Andrea Ficorella;Stefano Merzi;L. Parellada Monreal
2021-01-01
Abstract
Silicon photomultipliers (SiPMs) are becoming the detector of choice in many fields, including medical instrumentation, industry and scientific experiments. The sensitivity of SiPMs typically covers the entire visible range but, in some applications, sensitivity in the vacuum ultraviolet (VUV) or near infrared (NIR) range is required, posing significant challenges in the technology development and in the device design. Fondazione Bruno Kessler (FBK) is now involved in research programs and instrumental upgrades towards the realization of backside illuminated (BSI) SiPMs. A first demonstration of BSI SiPMs has been recently obtained. A batch of SiPM wafers was thinned to a final thickness of about 10 μm, a few microns in excess compared to the nominal epitaxial layer thickness. An anti-reflective coating was built on the backside and a glass carrier wafer was permanently bonded in order to provide mechanical stability. Although this was a preliminary attempt, mainly intended as a process demonstration, this batch of thinned substrate SiPMs provided an increased photon detection efficiency (PDE) in the NIR range when operated in BSI configuration. The increase in the PDE was of about 50% at 900 nm in devices with metal reflectors, compared to the same front side illuminated technology. Further developments are in progress at FBK towards a BSI SiPM technology optimized for VUV light detection. In several frontier physics experiments, the direct detection of scintillation light produced by liquid noble elements is needed, ranging from 80 nm (He and Ne) to 178 nm (Xe). A BSI SiPM approach could bring several advantages in these fields, such as more flexibility in the entrance window fabrication and the potential of exploiting 3D-integration strategies.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
