Radiation effects on CMOS image sensors with sub-2µm pinned photodiodes

A group of four commercial sensors with pixel pitches below 2μm has been irradiated with 60Co source at several total ionizing dose levels related to space applications. A phenomenological approach is proposed through behavior analysis of multiple sensors embedding different technological choices (pitch, isolation or buried oxide). A complete characterization including dark current, activation energy and temporal noise analysis allows to discuss about a degradation scheme

Radiation Effects on CMOS Image Sensors With Sub-2 µm Pinned Photodiodes

CMOS image sensor hardness under irradiation is a key parameter for application fields such as space or medical. In this paper, four commercial sensors featuring different technological characteristics (pitch, isolation or buried oxide) have been irradiated with 60Co source. Based on dark current and temporal noise analysis, we develop and propose a phenomenological model to explain pixel performance degradation

Rad Tolerant CMOS Image Sensor Based on Hole Collection 4T Pixel Pinned Photodiode

1.4μm pixel pitch CMOS Image sensors based on hole collection pinned photodiode (HPD) have been irradiated with 60Co source. The HPD sensors exhibit much lower dark current degradation than equivalent commercial sensors using an Electron collection Pinned Photodiode (EPD). This hardness improvement is mainly attributed to carrier accumulation near the interfaces induced by the generated positive charges in dielectrics. The pre-eminence of this image sensor based on hole collection pinned photodiode architectures in ionizing environments is demonstrated

Electrical Characterization of the Backside Interface on BSI Global Shutter Pixels with Tungsten-Shield Test Structures on CDTI Process

A new methodology is presented using well known electrical characterization techniques on dedicated single devices in order to investigate backside interface contribution to the measured pixel dark current in BSI CMOS image sensors technologies. Extractions of interface states and charges within the dielectric densities are achieved. The results show that, in our case, the density of state is not directly the source of dark current excursions. The quality of the passivation of the backside interface appears to be the key factor. Thanks to the presented new test structures, it has been demonstrated that the backside interface contribution to dark current can be investigated separately from other sources of dark current, such as the frontside interface, DTI (deep trench isolation), etc

Nanocellulose/bioactive glass cryogels as scaffolds for bone regeneration

A major challenge exists in the preparation of scaffolds for bone regeneration, namely, achieving simultaneously bioactivity, biocompatibility, mechanical performance and simple manufacturing. Here, cellulose nanofibrils (CNF) are introduced for the preparation of scaffolds taking advantage of their biocompatibility and ability to form strong 3D porous networks from aqueous suspensions. CNF are made bioactive for bone formation through a simple and scalable strategy that achieves highly interconnected 3D networks. The resultant materials optimally combine morphological and mechanical features and facilitate hydroxyapatite formation while releasing essential ions for in vivo bone repair. The porosity and roughness of the scaffolds favor several cell functions while the ions act in the expression of genes associated with cell differentiation. Ion release is found critical to enhance the production of the bone morphogenetic protein 2 (BMP-2) from cells within the fractured area, thus accelerating the in vivo bone repair. Systemic biocompatibility indicates no negative effects on vital organs such as the liver and kidneys. The results pave the way towards a facile preparation of advanced, high performance CNF-based scaffolds for bone tissue engineering

The Public Repository of Xenografts enables discovery and randomized phase II-like trials in mice

More than 90% of drugs with preclinical activity fail in human trials, largely due to insufficient efficacy. We hypothesized that adequately powered trials of patient-derived xenografts (PDX) in mice could efficiently define therapeutic activity across heterogeneous tumors. To address this hypothesis, we established a large, publicly available repository of well-characterized leukemia and lymphoma PDXs that undergo orthotopic engraftment, called the Public Repository of Xenografts (PRoXe). PRoXe includes all de-identified information relevant to the primary specimens and the PDXs derived from them. Using this repository, we demonstrate that large studies of acute leukemia PDXs that mimic human randomized clinical trials can characterize drug efficacy and generate transcriptional, functional, and proteomic biomarkers in both treatment-naive and relapsed/refractory disease

Development of a hole-based active pixel sensor and evaluation of its behavior under ionizing environment

Les capteurs d’images CMOS connaissent une croissance rapide vers des applications à fortes valeurs ajoutées. Certains marchés en devenir, comme les applications d’imagerie médicale,sont axés sur la tenue aux rayonnements ionisants. Des solutions de durcissement par dessin existent actuellement pour limiter les effets de ces dégradations. Cependant, ces dernières peuvent contraindre assez fortement certains paramètres du pixel. Dans ce contexte, cette thèse propose une solution novatrice de durcissement aux effets d’ionisation par les procédés.Elle suggère l’utilisation de pixels intégrant une photodiode pincée à collection de trous pour limiter la dégradation du courant d’obscurité : paramètre le plus sévèrement impacté lors d’irradiations ionisantes. Cette étude est donc premièrement centrée sur la modélisation et l’étude du courant d’obscurité sur des capteurs CMOS standards aussi bien avant qu’après irradiation. Ces dernières assimilées, un démonstrateur d’un capteur intégrant des pixels de1.4 μm à détection de trous est proposé et réalisé. Les résultats en courant d’obscurité, induit par la contribution des interfaces, montrent de belles perspectives avant irradiation. Ce capteur a d’ailleurs été utilisé pour effectuer une comparaison directe sous irradiation entre un capteur à détection de trous et d’électrons à design identique. Ces essais montrent une réduction significative du courant d’obscurité aux fortes doses. Des voies d’amélioration sont proposées pour améliorer l’efficacité quantique du capteur, principal point à optimiser pour des applications aussi bien grand public que médicales.CMOS image sensors are rapidly gaining momentum in high end applications. Some emerging markets like medical imaging applications are focused on hardening against ionizing radiation. Design solutions currently exist to mitigate the effects of these degradations. However, they may introduce additional limitations on pixel performances. In this context, this thesis proposes an innovative solution of hardening by process against ionization effects. It suggests using hole pinned photodiode pixels to mitigate the dark current degradation: one of the most severely impacted parameter during ionizing radiation. This study is first focused on the modeling and understanding of dark current variation on standard CMOS sensors before and after irradiation. Next, a sensor integrating hole-based 1.4 micron pixels is proposed and demonstrated. Dark current performances induced by interfaces contribution are promising before irradiation. A direct comparison under irradiation between hole and electron based sensors with similar design has been carried out. These experiments show a significant reduction in dark current at high doses. Ways of improvement are proposed to enhance the quantum efficiency of this sensor, the main area for improvement as well consumer as medical applications

Energy savings with advanced control of reciprocating liquid chillers

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