Mechanisms of Dark Current Increase and Pixel Anomalies Induced by 2-GeV Ta-Irradiation in 8T-CMOS Image Sensors

The space optoelectronic imaging systems are susceptible to the impact of high-energy particle irradiation during on-orbit operations, leading to dark current increase and various types of pixel anomalies, which degrades device performance. Heavy ion and proton irradiation experiments on 8T-CMOS image sensors (CISs) are conducted to investigate the characteristics of dark current distributions and hot pixels. Additionally, cold pixels are observed in 8T-image sensors. The results demonstrate that dark current increases with increasing fluence, coupled with stopping and range of ions in matter (SRIM) simulations, Coulombic elastic scattering can be identified as the main cause for dark current increases due to proton and heavy ion irradiations, and the value of scattering cross sections may ultimately lead to offsets in the universal damage factor. A common exponential behavior is observed; integrating heavy ions into the existing theoretical framework, temperature dependence, and annealing of exponential behavior are also discussed. Both hot pixels and cold pixels can be attributed to defects induced by particle irradiation, with the difference that the defects causing hot pixels are located near the pinned photodiode, while the defects causing cold pixels are located in a specific capacitance of the 8T-CMOS image sensor.