Total ionizing dose effects on I-V and noise characteristics of MOS transistors in a 0.18 μm CMOS Image Sensor process

This paper presents an investigation into total ionizing dose (TID) effects on I-V and noise characteristics of MOS transistors manufactured in a 0.18 μm CMOS Image Sensor (CIS) process. The CIS are intended for use in space science missions experiencing harsh radiation environments, such as ESA's forthcoming JUICE mission. Devices were therefore irradiated to various TID levels up to 1 Mrad. Following irradiation, significant leakage current and threshold voltage modification was observed, and this was found to be more severe for devices with small channel geometries. Noise spectral density measurements were also performed at the different irradiation steps. Noise in the smaller geometry devices was found to increase following irradiation, whereas for larger devices it was not significantly affected. These findings enable future assessment of the effects of TID on functional and electro-optical characteristics of high performance CIS designs for use in space.