Patrice Gergaud

A new white beam x-ray microdiffraction setup on the BM32 beamline at the European Synchrotron Radiation Facility

A white beam microdiffraction setup has been developed on the bending magnet source BM32 at the European Synchrotron Radiation Facility. The instrument allows routine submicrometer beam diffraction to perform orientation and strain mapping of polycrystalline samples. The setup features large source to optics distances allowing large demagnification ratios and small beam sizes. The optics of the beamline is used for beam conditioning upstream a secondary source, suppressing any possible interference of beam conditioning on beam size and position. The setup has been designed for an easy and efficient operation with position control tools embedded on the sample stage, a high magnification large aperture optical microscope, and fast readout detectors. Switching from the white beam mode to the monochromatic mode is made easy by an automatic procedure and allows the determination of both the deviatoric and hydrostatic strain tensors.

Catalyst preparation for CMOS-compatible silicon nanowire synthesis

Metallic contamination was key to the discovery of semiconductor nanowires, but today it stands in the way of their adoption by the semiconductor industry. This is because many of the metallic catalysts required for nanowire growth are not compatible with standard CMOS (complementary metal oxide semiconductor) fabrication processes. Nanowire synthesis with those metals that are CMOS compatible, such as aluminium and copper, necessitate temperatures higher than 450 degrees C, which is the maximum temperature allowed in CMOS processing. Here, we demonstrate that the synthesis temperature of silicon nanowires using copper-based catalysts is limited by catalyst preparation. We show that the appropriate catalyst can be produced by chemical means at temperatures as low as 400 degrees C. This is achieved by oxidizing the catalyst precursor, contradicting the accepted wisdom that oxygen prevents metal-catalysed nanowire growth. By simultaneously solving material compatibility and temperature issues, this catalyst synthesis could represent an important step towards real-world applications of semiconductor nanowires.

A hard x-ray nanoprobe for scanning and projection nanotomography

To fabricate and qualify nanodevices, characterization tools must be developed to provide a large panel of information over spatial scales spanning from the millimeter down to the nanometer. Synchrotron x-ray-based tomography techniques are getting increasing interest since they can provide fully three-dimensional (3D) images of morphology, elemental distribution, and crystallinity of a sample. Here we show that by combining suitable scanning schemes together with high brilliance x-ray nanobeams, such multispectral 3D volumes can be obtained during a single analysis in a very efficient and nondestructive way. We also show that, unlike other techniques, hard x-ray nanotomography allows reconstructing the elemental distribution over a wide range of atomic number and offers truly depth resolution capabilities. The sensitivity, 3D resolution, and complementarity of our approach make hard x-ray nanotomography an essential characterization tool for a large panel of scientific domains.

X-ray micro Laue diffraction tomography analysis of a solid oxide fuel cell

Through micro Laue tomography analysis, the depth-resolved cartographies (i) of NiO grains in a solid oxide fuel cell sample and (ii) of the full tensor of the deviatoric strain into a slice of a Ge sample are obtained.

X-ray μ-Laue diffraction analysis of Cu through-silicon vias: A two-dimensional and three-dimensional study

Here, white X-ray μ-beam Laue diffraction is developed and applied to investigate elastic strain distributions in three-dimensional (3D) materials, more specifically, for the study of strain in Cu 10 μm diameter–80 μm deep through-silicon vias (TSVs). Two different approaches have been applied: (i) two-dimensional μ-Laue scanning and (ii) μ-beam Laue tomography. 2D μ-Laue scans provided the maps of the deviatoric strain tensor integrated along the via length over an array of TSVs in a 100 μm thick sample prepared by Focused Ion Beam. The μ-beam Laue tomography analysis enabled to obtain the 3D grain and elemental distribution of both Cu and Si. The position, size (about 3 μm), shape, and orientation of Cu grains were obtained. Radial profiles of the equivalent deviatoric strain around the TSVs have been derived through both approaches. The results from both methods are compared and discussed.

Reaction of Ni film with In0.53Ga0.47As: Phase formation and texture

The solid-state reaction between Ni and In0.53Ga0.47As on an InP substrate was studied by X-ray diffraction (XRD) and scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy techniques. Due to the monocrystalline structural aspect of the so-formed intermetallic, it was necessary to measure by XRD a full 3D reciprocal space mapping in order to have a complete overlook over the crystalline structure and texture of the intermetallic. The formation of the intermetallic was studied upon several different Rapid Thermal Annealings on the as-deposited samples. Pole figures analysis shows that the intermetallic features a hexagonal structure (P63/mmc) with an NiAs-type (B8) structure. Although only one hexagonal structure is highlighted, the intermetallic exhibits two different domains characterized by different azimuthal orientations, axiotaxial relationship, and lattice parameters. The intermetallic phases seem to present a rather wide range of stoichiometry according to annealing temperat...

Combining high-resolution X-ray reciprocal space mapping and dark-field electron holography for strain analysis in 20 nm pMOS structures

In this paper we explore the benefit of combining High Resolution X-Ray Reciprocal Space Mapping (HR-RSM) and Dark-Field Electron Holography (DFEH) techniques for strain characterization of thin pMOS-like structures. We are able to simulate the measured HR-RSM from the displacement field extracted by DFEH. This is a first step developing High Resolution X-Ray Diffraction (HRXRD) as a viable technique for in-line strain metrology.

Contacts for monolithic 3D architecture: Study of Ni0.9Co0.1 silicide formation

In this work, we studied the solid-state reaction between a Ni0.9Co0.1 film and a silicon substrate. NiCo silicide is considered to substitute Ni- and NiPt-based silicides in 3D integration in order to extend the bottom transistor thermal stability. Thanks to the combined analysis of sheet resistance data, X-ray reflectivity spectra modelling, X-ray diffraction and wavelength dispersive X-ray fluorescence analyses on Ni0.9Co0.1/Si samples annealed at various temperatures, we were able to describe the phase sequence of the NiCo silicide formation.

Synchrotron radiation-based characterization of interconnections in microelectronics: recent 3D results

In microelectronics, more and more attention is paid to the physical characterization of interconnections, to get a better understanding of reliability issues like voiding, cracking and performance degradation. Those interconnections have a 3D architecture with features in the deep sub-micrometer range, requiring a probe with high spatial resolution and high penetration depth. Third generation synchrotron sources are the ideal candidate for that, and we show hereafter the potential of synchrotron-based hard x-ray nanotomography to investigate the morphology of through silicon vias (TSVs) and copper pillars, using projection (holotomography) and scanning (fluorescence) 3D imaging, based on a series of experiments performed at the ESRF. In particular, we highlight the benefits of the method to characterize voids, but also the distribution of intermetallics in copper pillars, which play a critical role for the device reliability. Beyond morphological imaging, an original acquisition scheme based on scanning Laue tomography is introduced. It consists in performing a raster scan (z,θ) of a sample illuminated by a synchrotron polychromatic beam while recording diffraction data. After processing and image reconstruction, it allows for 3D reconstruction of grain orientation, strain and stress in copper TSV and also in the surrounding Si matrix.

Towards synchrotron‐based nanocharacterization

The advent of 3rd generation synchrotron sources coupled with high efficiency x‐ray focusing optics opened new nanocharacterization possibilities. This paper is an overview of synchrotron‐based techniques that may be of interest for nanotechnology researchers. Although not exhaustive, it includes a general background of synchrotron principle and main x‐ray interactions before addressing nanoimaging possibilities. Three‐dimensional (3D) hard x‐ray multimodal tomography is now doable that allows producing 3D morphological, chemical and crystalline images with a sub‐100 nm resolution. Although the resolution is still limited with respect to electron imaging, it presents attractive features like depth resolution and non‐destructive exam. Besides imaging, diffraction also allows strain determination within microstructures and is illustrated here on 100 nm copper lines. Surface analysis is illustrated through X‐ray Photoelectron Emission Microscopy (XPEEM).