In-Pixel source follower transistor RTS noise behavior under ionizing radiation in CMOS image sensors

Abstract

This paper presents temporal noise measurement results for several total ionizing dose (TID) steps up to 2.19 Mrad of an image sensor designed with a 0.18-μm CMOS image sensor process. The noise measurements are focused on the random telegraph signal (RTS) noise due to the in-pixel source follower transistor of the sensor readout chain inducing noisy pixels. Results show no significant RTS noise degradation up to 300 krad of TID. Beyond this TID step, a limited RTS noise degradation is observed, and for the 2.19-Mrad step, an additional increase of total noise, including thermal, 1/f, and RTS noises, is noted. Noisy pixels have been studied for high TIDs, and three cases have been observed: 1) no change on RTS behavior; 2) creation of RTS behavior; and 3) modifications of RTS behavior.