WORKSHOP PAPER
Optoelectrical Performance Evolution of CMOS Image Sensors Exposed to Gamma Radiation
Abstract
This study presents the effects of ionizing radiation, up to 5 kGy, in several CMOS image sensors manufactured using a commercial 0.18 µm technology dedicated to imaging. The main focus is on the degradation caused by electron-hole pairs in the isolation oxides used in CMOS image sensors, leading to interface state generation and positive charge trapping. Experiments were conducted on 128x128-3T-pixel-CMOS image sensors with various designs, examining the impact of gamma rays on optoelectrical transfer function, spectral responsivity, and dark current. The results show a significant increase in dark current and saturation voltage, attributed to shallow trench isolations, which can be mitigated by using enclosed layout transistors for doses above 1 kGy. The study also observes a wavelength-dependent decrease in responsivity, which could be caused by an increase in surface recombination velocity or a change in the superficial layers' stack transmittance.Keywords
Ionizing radiation, CMOS image sensors, Radiation effects,References
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