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

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

Theoretical evaluation of MTF and charge collection efficiency in CCD and CMOS image sensor

Classical models used to calculate the Modulation Transfer function (MTF) of a solid-state image sensor generally use a sinusoidal type of illumination. The approach, described in this paper, consists in considering a point-source illumination to built a theoretical three dimensional model of the diffusion and the collection of photo-carriers created within the image sensor array. Fourier transform formalism is used for this type of illumination. Solutions allow to evaluate the spatial repartition of the charge density collected in the space charge region, i.e. to get the Pixel Response Function (PRF) formulation. PRF enables to calculate analytically both MTF and crosstalk at every needed wavelengths. The model can take into account a uniformly doped substrate and an epitaxial layer grown on a highly doped substrate. The built-in electric field induced by the EPI/Substrate doping gradient is also taken into account. For these configurations, MTF, charge collection efficiency and crosstalk proportion are calculated. The study is established in the case of photodiode pixel but it can be easily extended to pinned photodiode pixels and photogate pixels

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

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

Vision-based macroscopic pedestrian models

International audienceWe propose a hierarchy of kinetic and macroscopic models for a system consisting of a large number of interacting pedestrians. The basic interaction rules are derived from earlier work where the dangerousness level of an interaction with another pedestrian is measured in terms of the derivative of the bearing angle (angle between the walking direction and the line connecting the two subjects) and of the time-to-interaction (time before reaching the closest distance between the two subjects). A mean-field kinetic model is derived. Then, three different macroscopic continuum models are proposed. The first two ones rely on two different closure assumptions of the kinetic model, respectively based on a monokinetic and a von Mises-Fisher distribution. The third one is derived through a hydrodynamic limit. In each case, we discuss the relevance of the model for practical simulations of pedestrian crowds

Testosterone Hormone Replacement Therapy: State-of-the-Art and Emerging Technologies

In the human male, testosterone is the major circulating androgen. The clinical effects of androgen are numerous, and testosterone deficiency is associated with a number of clinical abnormalities. At present, a variety of preparations containing testosterone is available for the treatment of androgen deficiency. Ideally, those treatments have to produce and maintain physiologic serum concentrations of the hormone. This article reviews the current existing testosterone dosage forms on the market with their advantages and drawbacks and examines new and emerging technology developments concerning this therapy. In particular, the latest innovations in transdermal delivery are explore