Radiation-induced dark current increase in CMOS Active Pixel Sensors

In this paper we discuss the dark current increase in CMOS Active Pixel Sensors (APS) due to total dose and proton induced damage. We describe measurement results on several diodes that were used to investigate the degradation of the pixel photodiode under ionizing radiation. This study resulted in the design of radiation tolerant pixels that have proven to tolerate at least 200 kGy(Si) total dose from a Co-60 source. Standard APS sensors show already large degradation after less than 100 Gy(Si) due to a strong surface leakage current increase. Standard CMOS imagers were also evaluated with respect to proton induced damage. Highly energetic protons can displace atoms from their lattice position, giving rise to an increase in mean level of dark current and non-uniformity.