Cyril Langlois

TaxNy thin films with three different nitrogen concentrations are deposited by reactive DC magnetron sputtering on SiO2/Si substrates and annealed in nitrogen atmosphere at temperatures between 350 and 450 °C for 20 to 120 min. The purpose of this work is to determine how the initial nitrogen content affects the composition, structure, morphology, and electrical properties of the TaxNy films under thermal budgets relevant to back-end-of-line (BEOL) integration.,The as-deposited films show a progressive evolution of their crystalline phase from bcc TaN0.1 to hexagonal Ta2N/ε-TaN and then to fcc δ-TaN as the nitrogen content increases. This evolution is accompanied by a marked change in surface morphology and an increase in resistivity from 125.1 ± 2.3 to 268 ± 5.0 µΩ.cm. After annealing, the nitrogen-poor and intermediate films exhibit nitrogen redistribution, with a decrease in the interfacial nitrogen peak and an enrichment of the near-surface region, whereas the nitrogen-rich film remains essentially unchanged. The activation energies extracted from the diffusion analysis are 0.20 eV for the nitrogen-poor film and 0.34 eV for the intermediate film. Structural changes induced by annealing include lattice expansion in the nitrogen-poor film and recrystallization in the intermediate film. The resistivity increases after annealing for the nitrogen-poor and nitrogen-rich films, whereas the intermediate film shows only a limited variation.,The intermediate film exhibits the most favorable compromise between resistivity stability and nitrogen redistribution, making it the most suitable sample among those studied for thin film resistor applications. These results show that the initial nitrogen content strongly governs the annealing response of TaxNy thin films and their suitability for thin-film resistor applications.

Orientation mapping techniques such as electron backscatter diffraction (EBSD) and automated crystal orientation mapping technique (ACOM-TEM) rely on dedicated quality metrics to assess the reliability of crystallographic indexing at each pixel. The eCHORD technique (electron CHanneling ORientation Determination), which recovers crystalline orientations in a standard scanning electron microscope by matching experimental backscattered electrons intensity profiles against a database of theoretical profiles, currently lacks such a robust confidence indicator. This work introduces a confidence index for eCHORD orientation mapping based on the windowed normalized cross-correlation index (wNCC) between experimental and theoretical profiles evaluated over sliding angular windows. Unlike the Euclidean distance used in the standard indexing step, the wNCC is sensitive to local profile discrepancies and provides a per-pixel reliability estimate directly analogous to the confidence index in EBSD or the reliability index in ACOM-TEM. The index was validated on three materials—an aluminum alloy, a copper microelectronic pad, and an α-titanium sample—and across several acquisition and indexing conditions. It successfully identifies unreliable pixels at grain boundaries, surface defects, and within poorly indexed grains, and constitutes an effective confidence metric within the eCHORD framework.

The core indexing engine of the electron Channelling ORientation Determination (eCHORD) technique has been modified to significantly minimize indexation errors in the resulting orientation maps, thus enhancing accurate microstructure characterization. Orientation mapping using eCHORD involves acquiring a sequence of backscattered electron images by rotating the region of interest (ROI) within the scanning electron microscope, the sample being tilted in the range ∼10°–15°. Such an image series forms a data-cube from which intensity profiles can be extracted at each position in the ROI, reflecting the variation of the backscattered electron signal as a function of sample rotation. These profiles are compared to a database of theoretical profiles obtained by dynamical diffraction simulations. Here, the methodology consists of emphasizing the importance of diffraction peak positions in these profiles, by differentiating the data extracted from the backscattered electron images rather than using them in their raw form. The implementation of the profile derivative significantly improves the correspondence between experimental data and its theoretical counterpart. The characterization of sub-micron twin boundaries in a copper interconnect on a microelectronic chip provides insights into the effects of this indexing refinement. A comparison with Electron Back Scattered Diffraction data on a twinned nickel-based sample confirms the results.

Bimetallic nanoparticles (BNPs) are promising candidates for fundamental research and applications as their physico-chemical properties can in many cases be tuned continuously or enhanced with respect to the mono-metallic particles. Here we investigate the possibility of fabricating silver-indium and silver-aluminium BNPs in the range of 4-5 nm diameter and of varying stoichiometry by laser vaporization and gas condensation in the gas phase. We analyse their crystalline structure and segregation behaviour using transmission electron microscopy and probe their oxidation state in optical absorption measurements by tracking spectral changes of the localized surface plasmon resonance (LSPR). These complementary techniques show that, despite the small size and the high reactivity especially of aluminium, the BNPs form a silver-rich alloyed core surrounded by an oxide shell. Exposure to air leads to consecutive oxidation, whereas annealing the BNPs in a reducing atmosphere stabilizes the alloyed particle cores, as demonstrated by a narrow and blue-shifted LSPR. This is a first step towards the stabilization of non-oxidized bimetallic nanoparticles combining a noble and a trivalent metal.

Dislocation densities were measured on the very same samples using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (Electron Channeling Contrast Imaging (ECCI) and High angular Resolution-Electron Back Scattered Diffraction (HR-EBSD)) and X-Ray Diffraction. Those different methods do not observe the same type of dislocations, i.e. Statistically Stored Dislocations (SSD) and/or Geometrically Necessary Dislocations (GND). Some are direct measurements techniques such as ECCI and TEM imaging while other are undirect methods, namely HR-EBSD and XRD measurements. Therefore, a quantitative comparison of the measurements obtained using those four techniques on undeformed and deformed duplex steels is proposed. For low deformation, where the dislocation density is quite small ( imaging methods are rather performant, while XRD measurements suffer from high uncertainty levels. HR-EBSD measurements show results that are in good agreement with the other methods for those deformation levels. For higher deformation levels (with dislocation densities above ), imaging methods are not relevant anymore, due to the increasing uncertainty arising from local contrast variation and overlapping of dislocations. The different results obtained highlight the necessity to take a step back on each method used. Correctly defining what is to be measured (SSD or GND), in which condition (solid material or thin plate), the parameters (pixel size, area ...) and their bias is essential, especially if the objective is to use the measurement in a micromechanical model.