X-ray radiation effect on CMOS imagers with in-pixel buried-channel source follower

Abstract

This paper presents a CMOS image sensor (CIS) with pinned-photodiode 5T active pixels which use an in-pixel buried channel source follower (BSF) with an optimized row selector (RS). According to our previous work [1][2], using in-pixel BSFs with optimized RS can achieve significant pixel dark random noise reduction, i.e. 50% reduction, specially for random telegraph signal (RTS) noise, and an increase of the pixel output swing and dynamic range. With significant dark random noise reduction, in order to evaluate the performance for perspective space or medical imaging application, this proposed pixel structure using 0.18μm CMOS image sensor process is also further characterized under X-ray radiation. The results show that although X-ray radiation induced additional acceptor-like interface traps will increase dark random noise, the BSF pixels are able to constrain the dark random noise increase after X-ray radiation.

Development of medical imaging sensors

“…The experimental results show that compared with the conventional sensor structure, the new sensor structure has a larger dynamic output range, but the quantum efficiency of pinned photodiode in the detection of long-wave light is reduced due to the extra n-well. 84 In order to solve the problem of non-uniformity caused by sensor splicing, a new wafer scale CMOS APS that is capable of lownoise and high-dynamic range simultaneously was designed. Compared with mammography detectors commonly, the new detectors showed a uniformity in terms of contrast-to-noise ratio (CNR) among the highest.…”