Radiation Hardness Comparison of CMOS Image Sensor Technologies at High Total Ionizing Dose Levels

Abstract

The impact of the manufacturing process on the radiation-induced degradation effects observed in CMOS image sensors (CISs) at the MGy total ionizing dose (TID) levels is investigated. Moreover, the vulnerability of the partially pinned PHDs at moderate-to-high TIDs is evaluated for the first time to our knowledge (PHD stands for “photodiode”). It is shown that the 3T-standard partially pinned PHD has the lowest dark current before irradiation, but its dark current increases to ~1 pA at 10 kGy(SiO 2 ). Beyond 10 kGy(SiO 2 ), the pixel functionality is lost. The comparison between several CIS technologies points out that the manufacturing process impacts the two main radiation-induced degradations: the threshold voltage shift of the readout chain MOSFETs and the dark current increase. For all the tested technologies, 1.8-V MOSFETs exhibit the lower threshold voltage shift, and the nMOSFETs are the most radiation tolerant. Among all the tested devices, 1.8-V sensors achieve the best dark current performance. Several radiation-hardening-by-design solutions are evaluated at the MGy level to improve further the understanding of CIS radiation hardening at extreme TID.