The experiments of displacement damage effects on CMOS APS image sensors induced by neutron irradiation from a nuclear reactor are presented. The CMOS APS image sensors are manufactured in the standard 0.35 μm CMOS technology. The flux of neutron beams was about 1.33 × 108 n/cm2s. The three samples were exposed by 1 MeV neutron equivalent-fluence of 1 × 1011, 5 × 1011, and 1 × 1012 n/cm2, respectively. The mean dark signal (KD), dark signal spike, dark signal non-uniformity (DSNU), noise (VN), saturation output signal voltage (VS), and dynamic range (DR) versus neutron fluence are investigated. The degradation mechanisms of CMOS APS image sensors are analyzed. The mean dark signal increase due to neutron displacement damage appears to be proportional to displacement damage dose. The dark images from CMOS APS image sensors irradiated by neutrons are presented to investigate the generation of dark signal spike.

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The dark signal degradation of the CMOS image sensor (CIS) was induced by neutron radiation, and it was modeled by Geant4, which is a three-dimensional Monte Carlo code. The simplified model of the CIS array was established according to the actual pixel geometry, material, and doping concentration. Nuclear elastic interaction and capture interaction were included in the physical processes, and the displacement damage dose in the space charge region of the pixel was calculated. The mean dark signal and dark signal distribution were modeled using Geant4, and the physical mechanisms were analyzed. The modeling results were in good agreement with the experimental and theoretical results.