Single Event Effects in CMOS Image Sensors

In this work, 3T Active Pixel Sensors (APS) are exposed to heavy ions (N, Ar, Kr, Xe), and Single Event Effects (SEE) are studied. Devices were fully functional during exposure, no Single Event Latch-up (SEL) or Single Event Functional Interrupt (SEFI) happened. However Single Event Transient (SET) effects happened on frames: line disturbances, and half or full circular clusters of white pixels. The collection of charges in cluster was investigated with arrays of two pixel width (7 and 10 \textmu{}m), with bulk and epitaxial substrates. This paper shows technological and design parameters involved in the transient events. It also shows that STARDUST simulation software can predict cluster obtained for bulk substrate devices. However, the discrepancies in epitaxial layer devices are large - which shows the need for an improved model

Ductile damage of porous materials with two populations of voids

International audienceThis note presents an upper bound and an estimate for the yield yield function of a material with a rigid ideally plastic matrix and two scale cavities. The results are compared to numerical simulations. The laws of evolution of the two porosities are determined

Porous materials with two populations of voids under internal pressure: II. Growth and coalescence of voids

International audienceThis study is devoted to the mechanical behavior of polycrystalline materials with two populations of voids, small spherical voids located inside the grains and larger spheroidal voids located at the grain boundaries. In part I of the work, instantaneous effective stress-strain relations were derived for fixed microstructure. In this second part, the evolution of the microstructure is addressed. Differential equations governing the evolution of the microstructural parameters in terms of the applied loading are derived and their integration in time is discussed. Void growth results in a global softening of the stress-strain response of the material. A simple model for the prediction of void coalescence is proposed which can serve to predict the overall ductility of polycrystalline porous materials under the combined action of thermal dilatation and internal pressure in the voids

Total dose evaluation of deep submicron CMOS imaging technology through elementary device and pixel array behavior analysis

Ionizing radiation effects on CMOS image sensors (CIS) manufactured using a 0.18 µm imaging technology are presented through the behavior analysis of elementary structures, such as field oxide FET, gated diodes, photodiodes and MOSFETs. Oxide characterizations appear necessary to understand ionizing dose effects on devices and then on image sensors. The main degradations observed are photodiode dark current increases (caused by a generation current enhancement), minimum size NMOSFET off-state current rises and minimum size PMOSFET radiation induced narrow channel effects. All these effects are attributed to the shallow trench isolation degradation which appears much more sensitive to ionizing radiation than inter layer dielectrics. Unusual post annealing effects are reported in these thick oxides. Finally, the consequences on sensor design are discussed thanks to an irradiated pixel array and a comparison with previous work is discussed

Ionization versus displacement damage effects in proton irradiated CMOS sensors manufactured in deep submicron process

Proton irradiation effects have been studied on CMOS image sensors manufactured in a 0.18 μm technology dedicated to imaging. The ionizing dose and displacement damage effects were discriminated and localized thanks to 60Co irradiations and large photodiode reverse current measurements. The only degradation observed was a photodiode dark current increase. It was found that ionizing dose effects dominate this rise by inducing generation centers at the interface between shallow trench isolations and depleted silicon regions. Displacement damages are responsible for a large degradation of dark current non-uniformity. This work suggests that designing a photodiode tolerant to ionizing radiation can mitigate an important part of proton irradiation effects

Une méthode d’homogénéisation sécante généralisée pour des matériaux polycristallins viscoplastiques en déformations imposées

Homogenization estimates for viscoplastic polycrystals are derived by applying the generalized-secant linearization scheme of Liu and Ponte Castañeda (2004) to the constitutive description with strain rates as primary variables. The resulting estimates are thus particularly suitable for simulating mechanical processes where deformations are imposed and where the material softens. Their accuracy is preliminarily assessed in the context of a model material system. Good agreement with previous estimates is found.Des estimations relatives à l’homogénéisation de polycristaux viscoplastiques sont obtenues en appliquant la méthode de linéarisation sécante généralisée de Liu et Ponte Castañeda (2004) au cas d’une relation constitutive où les taux de déformation sont des variables primaires. Les estimations obtenues sont particulièrement adaptées pour simuler des chargements mécaniques où les déformations sont imposées et où le matériau s’adoucit. La précision de ces estimations est évaluée au préalable dans le cas d’un système matériau modèle. Un bon accord est obtenu avec des estimations antérieures.Facultad de IngenieríaDepartamento de Aeronáutic

Effective flow surface of porous materials with two populations of voids under internal pressure: II. full-field simulations

International audienceThis study is devoted to the effective plastic flow surface of a bi-porous material saturated by a fluid. Highly irradiated uranium dioxide is a typical example of such a material. In part I of this study, a GTN-type approximation of the effective plastic flow surface has been derived. In this second part, the predictions of this new model are compared with full-field numerical simulations performed with a numerical method based on Fast Fourier Transforms. This method is successfully applied to voided materials with a Gurson matrix where the voids are subjected to internal pressure. Different microstructures containing a large number of spherical or ellipsoidal voids are investigated. The deviation from isotropy of their mechanical response is measured by a new criterion

Multilevel RTS in proton irradiated CMOS image sensors manufactured in a deep submicron technology

A new automated method able to detect multilevel random telegraph signals (RTS) in pixel arrays and to extract their main characteristics is presented. The proposed method is applied to several proton irradiated pixel arrays manufactured using a 0.18um CMOS process dedicated to imaging. Despite the large proton energy range and the large fluence range used, similar exponential RTS amplitude distributions are observed. A mean maximum amplitude independent of displacement damage dose is extracted from these distributions and the number of RTS defects appears to scale well with total nonionizing energy loss. These conclusions allow the prediction of RTS amplitude distributions. The effect of electric field on RTS amplitude is also studied and no significant relation between applied bias and RTS amplitude is observed

Ionizing radiation effects on CMOS imagers manufactured in deep submicron process

We present here a study on both CMOS sensors and elementary structures (photodiodes and in-pixel MOSFETs) manufactured in a deep submicron process dedicated to imaging. We designed a test chip made of one 128×128-3T-pixel array with 10 µm pitch and more than 120 isolated test structures including photodiodes and MOSFETs with various implants and different sizes. All these devices were exposed to ionizing radiation up to 100 krad and their responses were correlated to identify the CMOS sensor weaknesses. Characterizations in darkness and under illumination demonstrated that dark current increase is the major sensor degradation. Shallow trench isolation was identified to be responsible for this degradation as it increases the number of generation centers in photodiode depletion regions. Consequences on hardness assurance and hardening-by-design are discussed

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