Deep sub micrometer imaging of defects in copper pillars by X-ray tomography in a SEM.

The potential of X-ray nanotomography hosted in a SEM in presented in this paper. In order to improve the detail detectability of this system, which is directly related to the X-ray source size, thin metal layers have been studied and installed in the equipment. A 3D resolution pattern has been created in order to determine the smallest detectable features by this setup. This sample is a 25 µm diameter copper pillar in which size-controlled holes have been milled using a plasma-focused ion beam. This pattern has then been scanned and the resulting 3D reconstruction demonstrates that the instrument is able to detect 500 nm diameter voids in a copper interconnection, as used in 3D integration.

Specifications for hard condensed matter specimens for three-dimensional high-resolution tomographies.

Tomography is a standard and invaluable technique that covers a large range of length scales. It gives access to the inner morphology of specimens and to the three-dimensional (3D) distribution of physical quantities such as elemental composition, crystalline phases, oxidation state, or strain. These data are necessary to determine the effective properties of investigated heterogeneous media. However, each tomographic technique relies on severe sampling conditions and physical principles that require the sample to be adequately shaped. For that purpose, a wide range of sample preparation techniques is used, including mechanical machining, polishing, sawing, ion milling, or chemical techniques. Here, we focus on the basics of tomography that justify such advanced sample preparation, before reviewing and illustrating the main techniques. Performances and limits are highlighted, and we identify the best preparation technique for a particular tomographic scale and application. The targeted tomography techniques include hard X-ray micro- and nanotomography, electron nanotomography, and atom probe tomography. The article mainly focuses on hard condensed matter, including porous materials, alloys, and microelectronics applications, but also includes, to a lesser extent, biological considerations.

Three-dimensional imaging of copper pillars using x-ray tomography within a scanning electron microscope: a simulation study based on synchrotron data.

While microelectronic devices are frequently characterized with surface-sensitive techniques having nanometer resolution, interconnections used in 3D integration require 3D imaging with high penetration depth and deep sub-micrometer spatial resolution. X-ray tomography is well adapted to this situation. In this context, the purpose of this study is to assess a versatile and turn-key tomographic system allowing for 3D x-ray nanotomography of copper pillars. The tomography tool uses the thin electron beam of a scanning electron microscope (SEM) to provoke x-ray emission from specific metallic targets. Then, radiographs are recorded while the sample rotates in a conventional cone beam tomography scheme that ends up with 3D reconstructions of the pillar. Starting from copper pillars data, collected at the European Synchrotron Radiation Facility, we build a 3D numerical model of a copper pillar, paying particular attention to intermetallics. This model is then used to simulate physical radiographs of the pillar using the geometry of the SEM-hosted x-ray tomography system. Eventually, data are reconstructed and it is shown that the system makes it possible the quantification of 3D intermetallics volume in copper pillars. The paper also includes a prospective discussion about resolution issues.

[Vascular access for intermittent haemodialysis. Use of a Sparks obturator. Preliminary technical report (author's transl)]. / Les voies d'abord vasculaire de l'hémodialyse périodique. Utilisation à cet effet, d'un mandrin de Sparks. Note technique préliminaire

It appears possible to envisage, and especially in patients where the vascular and in particular, venous system is defective, the insertion of a Sparks obturator as soon as the indication for haemodialysis is considered and before is indispensable. In the case of urgent haemodialysis, in most instances the nephrologist himself inserts a Scribner shunt in order to be able to dialyse his patient as rapidly as possible. There is no contraindication to the insertion, either at the same time or during the next few days, of an obturator which may be anastomosed to the vessels much later. All arterio-venous fistulae, all systems which may alter, should, in our opinion, be equipped in this way, so that as soon as maturation of the obturator has occurred immediate availability of an excellent means of access exists.