Dark Current Spectroscopy on Alpha Irradiated Pinned Photodiode CMOS Image Sensors

Abstract

International audienceDark Current Spectroscopy is tested for the first time on irradiated CMOS Image sensors (CIS) to detect and identify radiation-induced silicon bulk defects. Two different pinned photodiode CIS are tested: a 5MP Commercial-Off-The-Shelf (COTS) CIS from OmniVision (OV5647) and a 256x256 pixel custom CIS. These CISs are irradiated with alpha particles at various fluences and at two different particle energies in the custom CIS (4 MeV or < 500 keV). Several defect types are detected in both CIS (up to five in the custom CIS). The identity of the defects is investigated by measuring the activation energy of the dark current and the stability of the defects during an isochronal annealing. Two defects are identified in the custom CIS: the divacancy and the vacancy-phosphorus. This work proves that dark current spectroscopy can be used on irradiated CIS to detect and identify radiation-induced silicon bulk defects

Simulation of Single-Particle Displacement Damage in Silicon—Part III: First Principle Characterization of Defect Properties

“…Moreover, the activation energy that we obtained here (i.e. 0.65 eV) has also been measured in the literature (0.64 eV in averages) using Arrhenius law in CMOS [7] or the generation rate and DLTS in diodes [8] (a full review is given in [4] for 2V and other defects). Therefore, the measured activation energy of 0.64 eV could be ascribed to the switching between 2Va 4 and 2Va 2 configurations.…”

“…The pre-factor A is proportional to T 2 and estimated to be ln(A)≈36 at 300 K in our studied case, from the experimental value of the divacancy given in [7,17,6].The term ! is commonly named the activation energy needed for one electron to go from the valence band to the conduction band.…”

“…Moreover, measured energy levels and cross sections are different for the recombination rate observed in siliconbased solar cells or bipolar transistors. In addition, even if the probability of having ICCT can be linked to the number of defects centers in the cluster, see Refs [7] and [2], it is still unclear how to account quantitatively for the measured current. These questions will be the subject of future studies, as well as extending the calculations to other defects (1V, 3V, 4V and 1I, 2I, 4I).…”

“…The number of states in the band gap is difficult to predict and varies between zero and four in the studied defects 2V and 3I. The divacancy has been widely detected in CMOS after irradiation [7] and plays a crucial role as a DC generation center. In our calculations, the divacancy appears after one second of annealing, and we observe that it possesses a high number of metastable configurations.…”

“…the di-vacancy (2V) and the tri-interstitial (3I). Their properties are analyzed and compared with DC and DC-RTS measurements on CMOS Image Sensors (CIS) [6,7] and DLTS [8].…”