γ-ray And Electron Irradiation Effects On A CMOS Image Sensor

In this study, Co60radiation sources and DD1.2high-frequencyhigh-voltage electron accelerator were used to carry out g-ray and1MeV electronirradiation tests for the commercial LUPA4000CMOS image sensors. Roomtemperature and high temperature annealing experiments were carried out afterirradiation. The performance of the CMOS image sensor was evaluated underdifferent irradiation and annealing conditions and the performance variation ofthe CMOS image sensor was summarized after the test. The irradiation damagemechanism of the CMOS image sensor as well as the similarities and differencesof g-ray and electron irradiation effects were also discussed. It is expected toprovide an experimental basis for the establishment of space radiation effectsequivalent and simulation methods and for exploration of the image sensorprotection approach.The main properties of the CMOS image sensor were found to varysignificantly after g-ray irradiation. Dark signal and the readout noise increasedmonotonically with increasing radiation dose. Response non-uniformity and thenumber of dead pixels increased slowly under lower dose irradiation, and thenincreased rapidly after increasing the irradiation dose up to70krad. Signal tonoise ratio (SNR) decreased gradually with increasing irradiation dose. Afterannealing at room temperature, dark signal failed to restore significantly, but thehysteresis phenomenon of grow was observed during certain hours, while otherproperties exhibited a certain degree of recovery. All the properties of the CMOSimage sensor displayed significant recovery effect after annealing at100°C. Asthe annealing temperature reached200°C, the property parameters were found tobe closed to the level before g irradiation.It has been found that1MeV electron irradiation and g-rays exhibit a similarirradiation effect on the CMOS image sensor. Under an equivalent absorbed dose,electron irradiation has a more serious impact on the CMOS image sensor thang-ray irradiation. Compared with the γ-ray irradiation, the growth rate of the darksignal and readout noise is greater after1MeV electron irradiation. Electronirradiation and g-ray have the same effect on the CMOS image sensor when the irradiation dose is less than30krad, however, response non-uniformity and thenumber of dead pixels increased rapidly as (the CMOS image sensor) irradiatedby electron.The mechanism of the CMOS image sensor after irradiation damage wasalso discussed. It is shown that the increasing of effect was caused by1MeVelectronic irradiation along the chip thickness direction that absorbed doseunevenly and also caused by the absorbed dose of sensitive area was larger thang-ray. The drift of image sensor’s property parameters was mainly caused by theirradiation damage of photosensitive diode, and the damage of other pixeldevices also contributed to the irradiation effect.