Current Status and Development of CMOS SiPM for Scintillator-Based Radiation Detectors Toward All-Digital Sensors[invited]

Modern scintillator-based radiation detectors require silicon photomultipliers (SiPMs) with photon detection efficiency higher than 40% at 420 nm, possibly extended to the vacuum ultraviolet (VUV) region, single-photon time resolution (SPTR) < 100 ps, and dark count rate (DCR) < 150 kcps/mm(2) . To enable single-photon time stamping, digital electronics and sensitive microcells need to be integrated in the same CMOS substrate, with a readout frame rate higher than 5 MHz for arrays extending over a total area up to 4 mm x 4 mm. This is challenging due to the increasing doping concentrations at low CMOS scales, deep-level carrier generation in shallow trench isolation fabrication, and power consumption, among others. The advances at 350 and 110 nm CMOS nodes are benchmarked against available SiPMs obtained in CMOS and commercial customized technologies. The concept of digital multithreshold SiPMs with a single microcell readout is finally reported, proposing a possible direction toward fully digital scintillator-based radiation detectors.