Total-Ionizing Dose Effects on Charge Transfer Efficiency and Image Lag in Pinned Photodiode CMOS Image Sensors

Abstract

The total-ionizing dose (TID) effects on image lag in pinned photodiode CMOS image sensors are investigated thanks to various device variants in order to isolate the major radiationinduced effects on the charge transfer. It is shown that the main cause of the charge transfer degradation is the radiation-induced defects generation in the premetal dielectric (PMD) and in the transfer gate (TG) spacer vicinity which modifies the potential diagram at the photodiode/TG interface by the creation of a potential pocket retaining the electrons that are not transferred. For 0.1 kGy(SiO 2) < TID < 5 kGy(SiO 2), the potential pocket degrades the pixel which exhibits very good lag performances, whereas it improves the high lag pixels by creating a speedup implant enhancing the electron transfer or by reducing the spillback. For TID > 5 kGy(SiO 2), the defects generated in the PMD influence the whole photodiode potential inducing a pinning voltage increase and degrading the charge transfer by enlarging the potential pocket effect which becomes the main image lag source. The reported results clarify the impact of ionizing radiation on the charge transfer, suggesting radiation hardened by design solutions for future space or nuclear applications.

Proton and Gamma Radiation Effects on a Fully Depleted Pinned Photodiode CMOS Image Sensor

“…In PPD CISs, photo-generated carriers collected in the PPD are not completely transferred to the SN even in non-irradiated sensors. Incomplete charge transfer happens due to several reasons: long diffusion time in the PPD, potential barrier or pocket at the PPD-TG edge, charge trapping under the TG and charge spill-back from the SN to the PPD [27], [28]. Image lag was measured as the signal in the first sensor readout in darkness following illumination at a defined level in the previous image.…”

A Multiscale Denoising Framework Using Detection Theory with Application to Images from CMOS/CCD Sensors

“…While CMOS image sensing technology is revolutionizing the digital imaging by shrinking the pixel pitch [39], one of the major challenges includes reducing image noise at the time of acquisition [40]. In the case of CMOS imaging sensors, main sources of noise include sensor electronics and photon starvation.…”

Proton Radiation Effects of CMOS Image Sensors on Different Star Map Recognition Algorithms for Star Sensors

“…However, CMOS image sensors in star sensors are subject to cumulative effects and single-event transients by the widespread presence of protons in space. The cumulative effects cause the degradation of image sensor parameters such as dark current, uniformity, and full well capacity [6][7][8]. Moreover, protons can cause bulk defects inside the image sensor, resulting in hot pixels in the image.…”