Radiation damages in CMOS image sensors: testing and hardening challenges brought by deep sub-micrometer CIS processes

Abstract

This paper presents a summary of the main results we observed after several years of study on irradiated custom imagers manufactured using 0.18 μm CMOS processes dedicated to imaging. These results are compared to irradiated commercial sensor test results provided by the Jet Propulsion Laboratory to enlighten the differences between standard and pinned photodiode behaviors. Several types of energetic particles have been used (gamma rays, X-rays, protons and neutrons) to irradiate the studied devices. Both total ionizing dose (TID) and displacement damage effects are reported. The most sensitive parameter is still the dark current but some quantum efficiency and MOSFET characteristics changes were also observed at higher dose than those of interest for space applications. In all these degradations, the trench isolations play an important role. The consequences on radiation testing for space applications and radiation-hardening-by-design techniques are also discussed.

Pixel pitch and particle energy influence on the dark current distribution of neutron irradiated CMOS image sensors

“…Two different processes can contribute to the radiation-induced dark current in CIS: the ionization and the displacement damage. The ionization (not depicted in the schematic and not studied in this work), corresponds to the production of electron-hole pairs within the silicon oxide by a charged particle, which increases the silicon-oxide interface state density [21]. These states introduce energy levels in the bandgap of the silicon at the oxide interface, and act as Shockley Read Hall Recombination-Generation (SRH R-G) centers [22].…”

“…in the depleted volume of the pixel). The ionization, quantified by the Total Ionizing Dose (TID), leads to a homogeneous dark current increase in all the pixels of the irradiated CIS [21].…”

Study on the Availability of 4T-APS as a Video Monitor and Radiation Detector in Nuclear Accidents

“…Charges generated in the hit pixel lead to an increased grayscale value. We can study the radiation response of the APS with help of Equations (1) and (2). Figure 5 shows the mean grayscale value as a function of irradiation dose rate.…”

“…An APS with four transistors (4T) has better background noise and a faster shutter speed than an APS with three transistors. Moreover, because of the separation of the space charge region (SCR) away from the oxide, its radiation resistance is greater than both APS with three transistors and charge coupled device (CCD) pixel sensors [1][2][3][4]. The photodiode in the core of each CMOS 4T-APS is a pinned photodiode (PPD), which is used in more than 99% of APSs today [5] and is designed to detect visible light photons, but is intrinsically sensitive to gamma photons as well.…”

Optical and Electrical Simulations of Radiation-Hard Photodiode in 0.35μM High-Voltage CMOS Technology

“…They act as recombination centers, trapping the generated charge and thus increasing the Shockley-Read-Hall (SRH) recombination rate and the dark current. The effective way to make a device radiation tolerant towards NIEL effect is to collect charge via drift, in order to reduce the probability of charge trapping and to make the device more resilient towards displacement damage [9][10][11].…”