Random Telegraph Noises in CMOS Image Sensors Caused by Variable Gate-Induced Sense Node Leakage Due to X-Ray Irradiation

• Published in: IEEE journal of the Electron Devices Society 2019, Vol.7, p.227-238
• Main Authors: Chao, Calvin Yi-Ping, Wu, Thomas M.-H., Yeh, Shang-Fu, Chou, Kuo-Yu, Tu, Honyih, Lee, Chih-Lin, Yin, Chin, Paillet, Philippe, Goiffon, Vincent
• Format: Article
• Language: English
• Subjects: active pixel sensor (APS); Charge transfer; CMOS; CMOS image sensor (CIS); CMOS image sensors; Cold storage; correlated double sampling (CDS); Dark current; Dependence; Electric potential; Food irradiation; gate induced drain leakage (GIDL); Leakage; Logic gates; MOSFETs; pinned photodiode (PPD); Pixels; radiation damage; Radiation effects; Random noise (RN); random telegraph noise (RTN); random telegraph signal (RTS); Silicon dioxide; total ionizing dose (TID); variable junction leakage (VJL); variable retention time (VRT); Voltage; Voltage control; X ray irradiation; X-ray; X-ray imaging
• ISSN: 2168-6734; 2168-6734
• DOI: 10.1109/JEDS.2019.2893299

The effects of X-ray irradiation on the random noises, especially the random telegraph noises (RTN), of a 45-nm on 65-nm stacked CMOS image sensor with 8.3M 1.1 μm pixels are investigated. It is found that before X-ray irradiation the dominant type of RTN among the noisiest pixels is the source follower (SF) MOSFET channel RTN. In contrast, after X-ray irradiation up to a total ionizing dose of 1 Mrad(SiO 2 ), the RTN becomes dominated by the variable transfer-gate-induced sense node (SN) leakage. These two different types of RTN can be distinguished by their dependence on the transfer gate (TG) OFF voltage and the time between the correlated double sampling (CDS). The magnitude of the RTN from the variable SN leakage is proportional to the CDS time and can be suppressed effectively by increasing the TG OFF voltage, whereas the SF RTN is independent of the CDS time or the TG OFF voltage.