Benefitting from the development of semiconductor technology, complementary metal oxide semiconductor (CMOS) image sensors have been able to rival or even surpass charge-coupled devices (CCDs). With high integration, low power consumption, and strong radiation resistance, CMOS image sensors have become a mainstream imaging device in the fields of star tracking, remote sensing imaging, and astronomical observation, and play an important role in space missions. The large number of high-energy protons in the space radiation environment can cause radiation damage to CIS devices operating in orbit, leading to device performance degradation and even functional failure. Proton-induced radiation damage includes the total ionizing dose effect, displacement damage effect, and single event effect. The total ionization dose and displacement damage cause defects in the oxides, interface states, and bulk Si, resulting in permanent damage to the devices, which mainly produces the output signal of the transient disturbance, and the damage gradually recovers with time. Therefore, it is important to study the proton radiation effect of CIS to improve the reliability of CIS applications in space-irradiated environments. Proton irradiation experiments of CIS are conducted at different energies and fluences. The degradation of dark signal, non-uniformity of dark signal, random telegraph signal, and hot pixel is analyzed, and the influence of different defects on the degradation of device parameters is studied by simulation. These experiments and analysis will help designers improve the reliability of CIS applications in space radiation environments.

The irradiation experiment was carried out by using the 100 MeV proton cyclotron of China Institute of Atomic Energy, and the selected proton energy was 50 MeV and 90 MeV. The fluence is in the range of 6×10¹⁰-4.7×10¹¹ cm^-2, All pins of the CIS are unbiased during irradiation. The CIS model used in this experiment is CMV4000 which the pixel size is 5.5 μm×5.5 μm and the total number of effective pixels is 2048×2048, It adopts a 8 T pixel structure. The CIS parameter test is carried out on the irradiation effect parameter measurement system of photoelectric image sensor based on European standard EMVA1288. The tests before and after irradiation were carried out at room temperature. In this study, The data gray images are extracted and processed by image analysis software, and the change rules of the dark signal distribution, dark signal spikes, and random telegraph signal are obtained. The changes of electron density and generation rate in space charge region after adding different defects are obtained by Technology Computer-Aided Design (TCAD) simulation.

In present study, experiments of 50 MeV and 90 MeV proton irradiation on CIS are carried out to analyze the experimental law of CIS performance degradation induced by proton irradiation. The increase in irradiation fluence results in rising dark signals, and dark signal spikes. Under the same displacement damage dose, the increase of average dark signal and the distribution trend of dark signal are consistent after proton irradiation with different energy (Figs. 2 and 3). However, 50 MeV proton irradiation will produce more dark signal spikes and greater dark signal non-uniformity. This is because the cross sections of inelastic collisions between different energiy proton and Si are different, resulting in different types of defects, and dark signal spikes are mainly caused by complex cluster defects (Figs. 4 and 5). Proton irradiation will produce two-level and multi-level RTS in CIS pixel,which is related to the density and type of bulk defects in the space charge region (Figs. 6 and 7). The simulation results show that different types of defects affect the carrier generation rate in the space charge region, deep level defects and cluster defects lead to higher carrier generation rate, and the increase of generation rate improves the dark signal, which in turn leads to DSNU and RTS phenomena between pixels (Figs. 9 and 10).

In this paper, proton irradiation experiments with different energy and fluence were carried out with commercial 8 T CIS, and the degradation laws of CIS dark signal, DSNU, hot pixel and RTS induced by proton irradiation were studied. The results show that the average dark signal increases significantly with the increase of displacement damage dose. Under the same displacement damage dose, the average dark signal increases uniformly after proton irradiation with different energy, but a different number of hot pixels are produced. This is mainly because the cross section of nuclear interaction between protons and silicon with different energy is different, which produces different types of defects in pixel units, leading to the difference of dark signals between pixels and the phenomenon of DSNU and RTS between different pixels. Through TCAD simulation, it is confirmed that the point defect near the center of the band gap has higher carrier generation rate, the generation rate of cluster defect is also higher than that of simple point defect, and the increase of generation rate leads to the increase of dark signal. This study provides experimental data reference for the study of displacement damage mechanism of CIS protons with different energies, and more radiation experiments and simulations will be carried out in the future to further study the degradation law and damage mechanism of displacement damage sensitive parameters such as hot pixels and RTS after proton irradiation with different energies.