Development Of Silicon Photomultiplier With High Detection Efficiency And Low Time Jitter For PET

Silicon photomultiplier tube(SiPM)has become the core component of positron emission tomography(PET)technology to accurately realize disease diagnosis,metabolic monitoring,drug development and other functions at the molecular level due to its excellent performance of high detection efficiency and high time resolution.In this paper,based on the key performance of detection efficiency and time jitter of silicon photomultiplier tube,an electronic avalanche triggering structure with ultra-shallow junction and deep junction is proposed,and the prototype chip of silicon photomultiplier tube is developed by optimizing electric field morphology to improve avalanche triggering probability.The radiation damage mechanism of silicon photomultiplier elements is studied,and the pre-compensation structure is proposed.The feasibility of the precompensation structure for radiation reinforcement is proved by simulation and experiment.Specific research contents are as follows:1、Designed the structure of silicon photomultiplier tube for PET application requirements.In order to improve the detection efficiency of the device at 420 nm,p-on-n structure is proposed to realize ultra-shallow electron triggered avalanche structure by BF2 ion implantation.The electric field morphology is optimized,and the time jitter is reduced by steep electric field control method on the premise of ensuring the avalanche triggering probability.A deep trench isolation structure is adopted to optimize its distance from the avalanche zone,prevent edge breakdown and reduce cross talk between pixels.2、A single tube with a pixel period of 50 μm,90 μm and 170 μm was developed.The dark current was below 1 nA before the breakdown voltage,and the breakdown voltage was 9.2V.EMMI tests showed no significant edge breakdown.This is because the quenched resistance values are in agreement with the design values,showing a significant current quench effect.For the single tube with 50 μm pixel,the distance between the avalanche zone and the deep trench isolation structure is 2,3.5 and 6μm,respectively.Under the condition of 0.3V overbias,the signal rate decreases from 286 cps/μm2 to 197 cps/μm2.Test results of a 15×15 silicon photomultiplier array show that the breakdown voltage is consistent with that of a single tube,and the level of dark current is two orders of magnitude higher than that of a single tube.3、In order to solve the problem of radiation damage of silicon avalanche diode,a charge pre-compensation structure is proposed.The forward current and voltage characteristics,reverse breakdown voltage characteristics and dark current characteristics of the devices before and after irradiation are compared.The dark current is reduced by one order of magnitude,and the simulation results further reveal the effectiveness of irradiation reinforcement.