Study of dark current random telegraph signal in proton-irradiated backside illuminated CMOS image sensors

Abstract

The dark current random telegraph signal (DC-RTS) has been investigated in a four-transistor pinned photodiode 0.18-μm backside illuminated CMOS image sensor (BSI CIS). The sensors were irradiated by high energy protons of 50, 60 and 70 MeV, respectively. After exposure to protons, the radiation-induced variations of the number of RTS pixels, the number of RTS levels and transition maximum amplitude are analyzed. The effect of proton energy on RTS occurrence probability is studied using two types of theoretical models. Furthermore, DC-RTS dependence on the epitaxial layer thickness of the sensors is discussed, showing that there is no significant difference for DC-RTS phenomenon in different epitaxial layers.