Radiation-Induced Leakage Current and Electric Field Enhancement in CMOS Image Sensor Sense Node Floating Diffusions

Alexandre Le Roch (1) , Cédric Virmontois (2) , Philippe Paillet (3) , Jean-Marc Belloir (2) , Serena Rizzolo (1) , Federico Pace (1) , Clémentine Durnez (1) , Pierre Magnan (1) , Vincent Goiffon (1)

1 DEOS - Département Electronique, Optronique et Signal
2 CNES - Centre National d'Études Spatiales [Toulouse]
3 DAM/DIF - DAM Île-de-France

This study investigates the leakage currents as well as the leakage current random telegraph signals sources in sense node floating diffusions and their consequences on imaging performances specifically after exposure to high energy particle radiation. Atomic displacement damage and ionization effects are separately studied thanks to neutron and X-ray irradiations. Proton irradiations have been performed to simultaneously study displacement damage dose and total ionizing dose effects while being more representative of the space environment. The studied displacement damage doses range from 500 TeV.g-1 to 40 GeV.g-1 and the total ionizing dose ranges from 24 krad(SiO2) to 72 krad(SiO2). High magnitude electric field effects, such as transfer gate induced leakage current, are investigated to further understand the phenomena involved in floating diffusions while giving new insights on the electric field enhancement of the charge generation mechanisms. This work shows that floating diffusions are very sensitive to ionizing radiation because of the presence of depleted Si/SiO2 interfaces with high magnitude electric fields around the junction. On the other hand, displacement damage in the floating diffusions is a major source of high amplitude leakage current random telegraph signals and leakage current non-uniformity. Such radiation-induced degradations can prevent the use of CMOS image sensor with a long floating diffusion retention time (e.g. global shutter operating mode or burst imagers) in radiation environments.

Mots clés: CMOS Image Sensor; Charge Storage; Floating Diffusion; Sense Node; Leakage Current; Dark Current; Electric Field Enhancement; Random Telegraph Signal; Pinned PhotoDiode; Global Shutter; Total Ionizing Dose; Displacement Damage Dose

Domaines: Traitement du signal et de l'image [eess.SP]

Alexandre Le Roch, Cédric Virmontois, Philippe Paillet, Jean-Marc Belloir, Serena Rizzolo, et al.. Radiation-Induced Leakage Current and Electric Field Enhancement in CMOS Image Sensor Sense Node Floating Diffusions. IEEE Transactions on Nuclear Science, 2019, 66 (3), pp.616-624. ⟨10.1109/TNS.2019.2892645⟩. ⟨hal-02103366⟩