Non-ionizing radiation effects in a soft X-ray CMOS image sensor

Townsend-Rose, Charles; Buggey, Thomas; Ivory, James; Dazzazi, Imane; Stefanov, Konstantin and Hall, David (2024). Non-ionizing radiation effects in a soft X-ray CMOS image sensor. Journal of Astronomical Telescopes, Instruments, and Systems, 10(3), article no. 036002.

DOI: https://doi.org/10.1117/1.JATIS.10.3.036002

Abstract

CIS221-X is a prototype monolithic complementary metal-oxide-semiconductor (CMOS) image sensor, optimized for soft X-ray astronomy and developed for the proposed European Space Agency Transient High Energy Sky and Early Universe Surveyor (THESEUS) mission. One significant advantage of CMOS technology is its resistance to radiation damage. To assess this resistance, three backside-illuminated CIS221-X detectors have been irradiated with 10 MeV protons using the MC40 Cyclotron Facility at the University of Birmingham, United Kingdom. Each detector received 1/2, 1, and 2 THESEUS end-of-life proton fluences ( 6.65 × 10 8p+/cm2). One had already been exposed to ionizing radiation [up to 59.04 krad total ionizing dose (TID)] during a previous radiation campaign. Using unirradiated readout electronics, the electro-optical performance of each device has been measured before and after proton irradiation. No significant change was observed in the readout noise and image lag. An increase in mean dark current was recorded, as was an increase in the number of hot pixels. The degradation of CIS221-X performance due to non-ionizing radiation effects is similar to that of comparable CMOS image sensors and has been attributed to an increase in the number of bulk silicon defects.