NUV-HD SiPMs with Metal-filled Trenches

In this contribution we would like to present a breakthrough improvement of the optical crosstalk between SPADs in SiPMs. In the framework of a collaboration between FBK and Broadcom we developed narrow metal-filled trenches that greatly suppress the optical crosstalk while maintaining a high fill factor and, in turn, photon detection efficiency. In particular, the new metal in trench detector (NUV-HD-MT) features an internal crosstalk almost 10 times lower than previous NUV-HD FBK SiPMs and can operate up to 17 V of excess bias voltages without any divergence of the correlated noise. The higher operating bias compensates the small loss in fill factor due to the insertion of the metal layer in the trenches and allows the NUV-HD-MT to reach PDE in excess of 60% with 40 μm cells. Together with a SiPM layout optimized for timing, the extended bias range allows to operate the detector with higher gain and low level of correlated noise, improving the CTR performance below 90 ps using 4x4 mm2 detectors coupled to 3x3x5 mm3 LYSO:Ce crystals and readout by a conventional front-end. The characteristics described above allow this detector to be considered as a good candidate for the upgrade of ToF-PET machines.