Comparative Study of Low-Temperature and Room-Temperature Proton-Induced Dark Current and Annealing Effects on CMOS Image Sensors

This article compares the proton-induced dark current and annealing effects on CMOS image sensors (CISs) under room-temperature (RT-CIS, 298 K) and low-temperature (LT-CIS, 253 K) conditions. It is demonstrated that LT-CIS exhibits a higher dark current and produces more hot pixels than that of the RT-CIS after proton irradiation, as low temperature hinders defect mobility. The physical model of dark current established at room-temperature irradiation is verified on LT-CIS. Annealing effects occur at a relatively low temperature (i.e., 263 K) on LT-CIS, as evidenced by a reduction in both the mean dark current and the number of hot pixels. After high-temperature annealing, several discrete peaks are observed in the dark current distributions on both LT-CIS and RT-CIS, indicating that there is a difference in the defect characteristics for distinct irradiation temperatures. This difference is able to be identified using the dark current spectrum and activation energy test. Furthermore, a reverse annealing phenomenon (that is, dark current increase during annealing) was observed in both LT-CIS and RT-CIS when the annealing temperature reached 493 K. The observed phenomenon suggests that defects may reorder and form new stable defects at the elevated temperatures. The reverse annealing is likely associated with the formation of an oxygen-vacancy complex (V2O).