Innovation in ion beam analysis for nanoelectronic materials

Nanoelectronics relies more and more on novel materials and architectures for technology advancements in terms of power, cost and area. The device functionalities depend on the composition and the amount of impurities of the device materials, whereby controlling the concentrations with high accuracy is essential to tailor the device performances. Besides, it is crucial to characterize devices with relevant dimensions and substrates as it is demonstrated that compositions may be size dependent, and atom areal densities may be substrate dependent. Ion beam analysis, in particular elastic recoil detection (ERD) and Rutherford backscattering spectrometry (RBS), is recognized to offer compositional quantification as a function of depth in the target. However, in ion beam analysis, mass and depth resolutions are limited by the detector performance. Lateral resolution is hampered by the broad primary beam dimensions, whereby conventional RBS analyses are on blanket layers. Sensitivity to atom areal densities is limited by the counting statistics and background noise. The objective of this thesis work is to extend ion beam analysis towards next generation nanoelectronics devices through four major advancements, namely high mass resolution, sensitivity, lateral and depth resolution. The mass resolution in elastic recoil detection is limited by the detector resolution performance, whereby neighboring elements in the periodic table have overlapping recoil distributions. This hampers the quantification of the atom areal densities for recoils with small mass difference. A mass discrimination procedure is developed which deconvolves the overlapping recoil signals. We show that 1 amu mass resolution in ERD can be attained with the mass discrimination algorithm. In Rutherford backscattering spectrometry, the sensitivity to low amounts of materials is enhanced by reducing the background due to pile-up effects, hence by increasing the signal-to-noise ratio. Pile-up background strongly depends on the count rate, whereby improving this background requires low count rates. The count rate is reduced either through the segmentation of the detector active area and the data acquisition by multiple devices or through the dispersive power of a magnetic spectrometer used to deviate the substrate signal outside of the detector area, thus suppressing the dominant backscattering yield in a conventional RBS spectrum. With such advancements, it is feasible to probe the defectivity at the early stages of area selective atomic layer depositions on plasma treated substrates. Furthermore, RBS is extended towards the analysis of confined nanostructures with lateral dimensions of as low as 16 nm. The broad beam is utilized to probe simultaneously a multitude of periodically repeated nanostructures embedded in a foreign matrix, whereas the mass difference between the elements in the fins and in the matrix is used to isolate the information from the nanostructure. The extracted compositions average over the ensemble of probed devices, thereby providing a statistically relevant analysis. Finally, the RBS depth resolution is conventionally limited at 10-15 nm by the detector energy resolution. In a magnetic spectrometer, ions are spatially dispersed as a function of their magnetic rigidities, thus energies, whereby high energy resolution is enabled by a position sensitive detector which records the ion position on the focal plane with high spatial resolution. The superior energy resolution allows a depth resolution of 2.7 nm of cobalt. When the detector resolution is improved, other sources of energy broadening must be considered, namely the primary beam broadening, the geometrical broadening and the energy spread induced by sample modifications. These contributions are discussed and improvements are proposed to minimize the energy broadenings towards high energy resolution.status: publishe

Rutherford backscattering spectrometry analysis of InGaAs nanostructures

© 2019 Author(s). In this work, the authors demonstrate that Rutherford backscattering spectrometry (RBS) can be extended from a metrology concept applied to blanket films toward a method to analyze confined nanostructures. By a combination of measurements on an ensemble of devices and extensive simulations, it is feasible to quantify the composition of InGaAs nanostructures (16-50 nm) embedded periodically in an SiO 2 matrix. The methodology is based on measuring multiple fins simultaneously while using the geometrical shape of the structures, obtained from a transmission electron microscopy analysis, as input for a multitude of trajectory calculations. In this way, the authors are able to reproduce the RBS spectra and to demonstrate the sensitivity of the RBS spectra to the quantitative elemental composition of the nanostructures and to variations of their shape and mean areal coverage down to one nanometer. Thus, the authors establish RBS as a viable quantitative characterization technique to probe the composition and structure of periodic arrays of nanostructures.status: publishe

Rickettsia conorii Subspecies israelensis in Captive Baboons

: Hamadryas baboons (Papio hamadryas) may transmit zoonotic vector-borne pathogens to visitors and workers frequenting zoological parks. We molecularly screened 33 baboons for vector-borne pathogens. Three (9.1%) of 33 animals tested positive for Rickettsia conorii subspecies israelensis. Clinicians should be aware of potential health risks from spatial overlapping between baboons and humans

Rutherford backscattering spectrometry analysis of InGaAs nanostructures

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Serologic and molecular characterization of tickborne pathogens in lions (Panthera leo) from the fasano Safari Park, Italy

Lions (Panthera leo) are an endangered species threatened by illegal hunting, habitat loss, and infectious diseases. Little is known about the tick-borne pathogens that infect lions and could contribute to population declines. The objective of this study was to characterize Rickettsia spp., Anaplasma phagocytophilum, and Coxiella burnetii infections in 10 lions from the Fasano Safari Park in Italy by serology, polymerase chain reaction, and sequence analysis. Although animals did not show clinical signs of tick-borne diseases, evidence of infection with C. burnetii, spotted fever group Rickettsia sp., and A. phagocytophilum were found in 50%, 20%, and 10% of the lions, respectively. One of the lions tested positive for all three pathogens. This study is the first report of molecular evidence of infection with C. burnetii, Rickettsia sp., and A. phagocytophilum in lions and provides evidence that these felids become infected and serve as hosts for tick-transmitted bacteria.This research was funded by The Ministry of Health, Italy (project IZSSi 1/04); the Junta de Comunidades de Castilla–La Mancha (JCCM), Spain (project 06036-00 ICS-JCCM); and the Ministry of Science and Education, Spain (project AGL2005-07401). V. Naranjo was funded by Consejería de Educación, JCCM, Spain.Peer reviewe