Translational models for vascular cognitive impairment: a review including larger species.

BACKGROUND: Disease models are useful for prospective studies of pathology, identification of molecular and cellular mechanisms, pre-clinical testing of interventions, and validation of clinical biomarkers. Here, we review animal models relevant to vascular cognitive impairment (VCI). A synopsis of each model was initially presented by expert practitioners. Synopses were refined by the authors, and subsequently by the scientific committee of a recent conference (International Conference on Vascular Dementia 2015). Only peer-reviewed sources were cited. METHODS: We included models that mimic VCI-related brain lesions (white matter hypoperfusion injury, focal ischaemia, cerebral amyloid angiopathy) or reproduce VCI risk factors (old age, hypertension, hyperhomocysteinemia, high-salt/high-fat diet) or reproduce genetic causes of VCI (CADASIL-causing Notch3 mutations). CONCLUSIONS: We concluded that (1) translational models may reflect a VCI-relevant pathological process, while not fully replicating a human disease spectrum; (2) rodent models of VCI are limited by paucity of white matter; and (3) further translational models, and improved cognitive testing instruments, are required

Nanoscale effect on the formation of the amorphous Ni silicide by rapid thermal annealing from crystalline and pre-amorphized silicon

International audienceThe Ni monosilicide alloyed with Pt is widely used as contact material in advanced microelectronics devices and a good knowledge of silicide formation kinetics is required for the process control. In this work, the nature, and the growth kinetics of the first silicide obtained during the solid-state reaction between the Ni0.9Pt0.1 and the Si are studied for different pre amorphization implant (PAI) conditions as well as for a reference sample without PAI. Reactions between a 10 nm thick Ni0.9Pt0.1 film and Si (100) substrate are analyzed after several rapid thermal anneals (RTA). The nature of the first silicide is determined by Fourier Transform of TEM images and by chemical TEM-EDX analyses. The silicide growth behavior is determined by measuring the silicide thickness by X ray reflectivity (XRR) after the partial reaction induced by RTAs at different temperatures and times. To determine the growth law, the linear parabolic model is first considered but a nonlinear reactive diffusion model must be developed to accurately reproduce the experimental results. From this model, the effective diffusion coefficient as well as its activation energy were determined for the three samples with PAI and the reference sample without PAI. The influence of the driving force on the nonlinear diffusion for thin films is proved, and the impact of the amorphous substrate on the kinetics parameters is quantified and compared to the literature

On the influence of Ni(Pt)Si thin film formation on agglomeration threshold temperature and its impact on 3D imaging technology integration

Ni(10 at.% Pt) monosilicide is used as contact in microelectronics but suffers from degradation at relatively low temperatures due to agglomeration. Recent results obtained on 28 nm-FDSOI microelectronics devices have demonstrated severe yield loss after an anneal at 550 °C/2 h linked to Ni(Pt)Si film dewetting. Such agglomeration thermal budget is 100 °C lower than the ones measured on blanket wafers with in-situ or exsitu four-point probe measurements. In this context, the aim of this paper is to investigate the effect Ni(Pt)Si formation process on the Ni(Pt)Si agglomeration using different approaches as (i) the classical one in which one anneal is applied to form silicide and leads also to agglomeration, (ii) the silicide formation through the standard SALICIDE process, "Self-Aligned Silicide", and a subsequent anneal to induce agglomeration, and (iii) the standard SALICIDE process for silicide formation followed by an encapsulation of the top silicide surface by a SiN layer as applied in devices, and submitted finally to the agglomeration anneal. Our work demonstrated that the film thermal stability is influenced by the sequencing of the selective etch (SE) in the formation process and whether it is formed by a single or a double anneal. Another conclusion of this work is that four-point probe measurements are not sensitive enough to well estimate the real starting point of agglomeration phenomenon which is detrimental for devices (holes formation at the triple junctions). Some additional characterizations such as tilted Scanning Electron Microscopy (tilted SEM) are deeply needed for an accurate determination of agglomeration thermal budget. This study allows clarifying the main parameters leading to agglomeration: the film thickness and the grain size appear to be the more important ones

Observation of HfO2 thin films by deep UV spectroscopic ellipsometry

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Additional Siconi™ pre-clean for reliable TiSix contacts in advanced imager technologies

In the frame of advanced imager technology development, Ti-silicide direct contacts are commonly used in the device integration in the very near environment of pixel area. Therefore, a low resistivity, high yield, and reliability are the principal requirements for these integrated contacts. As previously reported, the Ti silicide formation at the bottom of contact is quite dependant to the surface preparation scheme. In this paper, various pre-clean processes combined with Ar plasma and Siconi™ etchings are in-depth analysed based on blanket wafers and devices characterizations through ellipsometry, TEM-EDX, contact resistivity, yield and reliability measurements. Strong variations of limited yield and contacts chain resistance are then observed. Based on these results, the lower contact resistance with an improved yield is finally achieved for a pre-clean sequence including Ar plasma before an adapted Siconi™ clean. So far, for this new process sequence, the high wafer temperature during the Siconi™ etch step induces lower etch amount which is corrected by a longer “pre-etch” time. Keywords: TiSi2, Silicide-last, Direct contacts, Imagers, Ar plasma, Pre-clean, Siconi, Yield, Contact resistanc

Physical Characterization of HfxTiyOz Thin Films Deposited on Si by Pulsed Injection MOCVD

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IMPACT OF NANOSECOND LASER ENERGY DENSITY ON THE C40-TiSi2 FORMATION AND C54-TiSi2 TRANSFORMATION TEMPERATURE.

International audienceThe formation of Ti based contacts in new image sensors CMOS technologies is limited by the requirement of low thermal budget. The objectives for these new 3D-technologies are to promote ohmic, low resistance, repeatable and reliable contacts by keeping the process temperature as low as possible. In this work, UV-nanosecond laser annealing were performed before classical rapid thermal annealing (RTA) to promote the formation at lower RTA temperatures of the low resistivity C54-TiSi2 phase. The laser energy density was varied from 0.30 to 1.00 J/cm² with 3 pulses in order to form the C40-TiSi2 phase and finally to obtain the C54-TiSi2 phase by a subsequent RTA at low temperature. The formed Ti-silicides were characterized by four-point probe measurements, X-Ray Diffraction, Transmission Electron Microscopy and Atom Probe Tomography. A threshold in the laser energy density for the formation of the C40-TiSi2 is observed at an energy density of 0.85 J/cm² for the targeted TiN/Ti stack on blanket wafers. The C40-TiSi2 formation by laser annealing prior to RTA enables to reduce the formation temperature of the C54-TiSi2 phase by 150°C in comparison to a single RTA applied after the Ti/TiN deposition. This specific phase sequence is only observed for a laser energy density close to 0.85 J/cm². At higher energy densities, the presence of C49-TiSi2 or a mix of C49-TiSi2 and C54-TiSi2 is observed. The underlying mechanisms for the phase sequence and formation are discussed in details

Industrial characterization of scatterometry for advanced APC of 65 nm CMOS logic gate patterning

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Critical thickness threshold in HfO2 layers

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Chemical interface analysis of as grown HfO2 ultrathin films on SiO2

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