Analysis of total dose-induced dark current in CMOS image sensors from interface state and trapped charge density measurements

The origin of total ionizing dose induced dark current in CMOS image sensors is investigated by comparing dark current measurements to interface state density and trapped charge density measurements. Two types of photodiode and several thick-oxide-FETs were manufactured using a 0.18-µm CMOS image sensor process and exposed to 10-keV X-ray from 3 krad to 1 Mrad. It is shown that the radiation induced trapped charge extends the space charge region at the oxide interface, leading to an enhancement of interface state SRH generation current. Isochronal annealing tests show that STI interface states anneal out at temperature lower than 100°C whereas about a third of the trapped charge remains after 30 min at 300°C

Evidence of a novel source of random telegraph signal in CMOS image sensors

This letter reports a new source of dark current random telegraph signal in CMOS image sensors due to meta-stable Shockley-Read-Hall generation mechanism at oxide interfaces. The role of oxide defects is discriminated thanks to the use of ionizing radiations. A dedicated RTS detection technique and several test conditions (radiation dose, temperature, integration time, photodiode bias) reveal the particularities of this novel source of RTS

New source of random telegraph signal in CMOS image sensors

We report a new source of dark current random telegraph signal in CMOS image sensors due to meta-stable Shockley-Read-Hall generation mechanism at oxide interfaces. The role of oxide defects is discriminated thanks to the use of ionizing radiations

Generic radiation hardened photodiode layouts for deep submicron CMOS image sensor processes

Selected radiation hardened photodiode layouts, manufactured in a deep submicron CMOS Image Sensor technology, are irradiated by 60Co gamma-rays up to 2.2 Mrad(SiO2) and studied in order to identify the most efficient structures and the guidelines (recess distance, bias voltage) to follow to make them work efficiently in such technology. To do so, both photodiode arrays and active pixel sensors are used. After 2.2 Mrad(SiO2), the studied sensors are fully functional and most of the radiation hardened photodiodes exhibit radiation induced dark current values more than one order of magnitude lower than the standard photodiode

Displacement Damage Effects in Pinned Photodiode CMOS Image Sensors

This paper investigates the effects of displacement damage in Pinned Photodiode (PPD) CMOS Image Sensors (CIS) using proton and neutron irradiations. The DDD ranges from 12 TeV/g to ${1.2 times 10^{6}}$ TeV/g. Particle fluence up to $5 times 10^{14}$ n.cm $^{-2}$ is investigated to observe electro-optic degradation in harsh environments. The dark current is also investigated and it would appear that it is possible to use the dark current spectroscopy in PPD CIS. The dark current random telegraph signal is also observed and characterized using the maximum transition amplitude

Analyse des effets des déplacements atomiques induits par l'environnement radiatif spatial sur la conception des imageurs CMOS

L' imagerie spatiale est aujourd'hui un outil indispensable au développement durable, à la recherche et aux innovations scientifiques ainsi qu à la sécurité et la défense. Fort de ses excellentes performances électro-optiques, de son fort taux d intégration et de la faible puissance nécessaire à son fonctionnement, le capteur d images CMOS apparait comme un candidat sérieux pour ce type d application. Cependant, cette technologie d imageur doit être capable de résister à l environnement radiatif spatial hostile pouvant dégrader les performances des composants électroniques. Un nombre important d études précédentes sont consacrées à l impact des effets ionisants sur les imageurs CMOS, montrant leur robustesse et des voies de durcissement face à de telles radiations. Les conclusions de ces travaux soulignent l importance d étudier les effets non-ionisants, devenant prépondérant dans les imageurs utilisant les dernières évolutions de la technologie CMOS. Par conséquent, l objectif de ces travaux de thèse est d étudier l impact des effets non-ionisants sur les imageurs CMOS. Ces effets, regroupés sous le nom de déplacements atomiques, sont étudiés sur un nombre important de capteurs d images CMOS et de structures de test. Ces dispositifs sont conçus avec des procédés de fabrication CMOS différents et en utilisant des variations de règle de dessin afin d investiguer des tendances de dégradation commune à la technologie d imager CMOS. Dans ces travaux, une équivalence entre les irradiations aux protons et aux neutrons est mise en évidence grâce à des caractéristiques courant-tension et des mesures de spectroscopie transitoire de niveau profond. Ces résultats soulignent la pertinence des irradiations aux neutrons pour étudier les effets non-ionisants. L augmentation et la déformation de l histogramme de courant d obscurité ainsi que le signal télégraphique aléatoire associé, qui devient le facteur limitant des futures applications d imagerie spatiale, sont évalué et modélisés. Des paramètres génériques d évaluation des effets des déplacements atomiques sont mis en évidence, permettant de prévoir le comportement des capteurs d images CMOS en environnement radiatif spatial. Enfin, des méthodes d atténuation et des voies de durcissement des imageurs CMOS limitant l impact des déplacements atomiques sont proposées.Today, space imaging is an essential tool for sustainable development, research and scientific innovation as well as security and defense. Thanks to their good electro-optic performances and low power consumption, CMOS image sensors are serious candidates to equip future space instruments. However, it is important to know and understand the behavior of this imager technology when it faces the space radiation environment which could damage devices performances. Many previous studies have been focused on ionizing effects in CMOS imagers, showing their hardness and several hardening-by-design techniques against such radiations. The conclusions of these works emphasized the need to study non-ionizing effects which have become a major issue in the last generation of CMOS image sensors. Therefore, this research work focuses on non-ionizing effects in CMOS image sensors. These effects, also called displacement damage, are investigated on a large number of CMOS imagers and test structures. These devices are designed using several CMOS processes and using design rule changes in order to observe possible common behaviors in CMOS technology. Similarities have been shown between proton and neutron irradiations using current-voltage characteristics and deep level transient spectroscopy. These results emphasize the relevance of neutron irradiations for an accurate study of the non-ionizing effects. Then, displacement damage induced dark current increase as well as the associated random telegraph signal are measured and modeled. Common evaluation parameters to investigate displacement damage are found, allowing imager behavior prediction in space radiation environment. Finally, specific methods and hardening-by-design techniques to mitigate displacement damage are proposed.TOULOUSE-ISAE (315552318) / SudocSudocFranceF

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

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 eficiency 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

Identification of radiation induced dark current sources in pinned photodiode CMOS image sensors

This paper presents an investigation of Total Ionizing Dose induced dark current sources in Pinned PhotoDiodes (PPD) CMOS Image Sensors based on pixel design variations. The influence of several layout parameters is studied. Only one parameter is changed at a time enabling the direct evaluation of its contribution to the observed device degradation. By this approach, the origin of radiation induced dark current in PPD is localized on the pixel layout. The PPD peripheral STI does not seem to play a role in the degradation. The PPD area and an additional contribution independent on the pixel dimensions appear to be the main sources of the TID induced dark current increase

Similarities Between Proton and Neutron Induced Dark Current Distribution in CMOS Image Sensors

Several CMOS image sensors were exposed to neutron or proton beams (displacement damage dose range from 4 TeV/g to 1825 TeV/g) and their radiation-induced dark current distributions are compared. It appears that for a given displacement damage dose, the hot pixel tail distributions are very similar, if normalized properly. This behavior is observed on all the tested CIS designs (4 designs, 2 technologies) and all the tested particles (protons from 50 MeV to 500 MeV and neutrons from 14 MeV to 22 MeV). Thanks to this result, all the dark current distribution presented in this paper can be fitted by a simple model with a unique set of two factors (not varying from one experimental condition to another). The proposed normalization method of the dark current histogram can be used to compare any dark current distribution to the distributions observed in this work. This paper suggests that this model could be applied to other devices and/or irradiation conditions

Displacement damage effects due to neutron and proton irradiations on CMOS image sensors manufactured in deep submicron technology

Displacement damage effects due to proton and neutron irradiations of CMOS image sensors dedicated to imaging are presented through the analysis of the dark current behavior in pixel arrays and isolated photodiodes. The mean dark current increase and the dark current nonuniformity are investigated. Dark current histogram observations are compared to damage energy distributions based on GEANT 4 calculations. We also discuss, through annealing analysis, which defects could be responsible for the dark current in CMOS image sensors