Michael Feser

Near field stacking of zone plates for reduction of their effective zone period

Here we analyze the potential of a new fabrication method for high resolution zone plates with high aspect ratios based on near field stacking of frequency doubled atomic layer deposited (ALD) zone plates. The proposed method enables reduction of the effective zone period by a factor of four with two zone plate layers compared to the initial e-beam lithography exposed outermost zone period. It also overcomes the problem that very small zone widths with high aspect ratios have to be fabricated for high-resolution hard X-ray microscopy. Using rigorous coupled wave theory, we have analyzed the diffraction behavior of these near field stacked zone plates and investigated strategies to optimize fabrication parameters to compensate for separation of stacked zone plates. The calculations performed for 8 keV photon energy and effective outermost zone widths of 28 nm and 15 nm predict diffraction efficiencies ≥ 20% suggesting that such optics could find widespread practical applications.

X-ray microscopy for in situ characterization of 3D nanostructural evolution in the laboratory

X-ray microscopy (XRM) has emerged as a powerful technique that reveals 3D images and quantitative information of interior structures. XRM executed both in the laboratory and at the synchrotron have demonstrated critical analysis and materials characterization on meso-, micro-, and nanoscales, with spatial resolution down to 50 nm in laboratory systems. The non-destructive nature of X-rays has made the technique widely appealing, with potential for “4D” characterization, delivering 3D micro- and nanostructural information on the same sample as a function of sequential processing or experimental conditions. Understanding volumetric and nanostructural changes, such as solid deformation, pore evolution, and crack propagation are fundamental to understanding how materials form, deform, and perform. We will present recent instrumentation developments in laboratory based XRM including a novel in situ nanomechanical testing stage. These developments bridge the gap between existing in situ stages for micro scale XRM, and SEM/TEM techniques that offer nanometer resolution but are limited to analysis of surfaces or extremely thin samples whose behavior is strongly influenced by surface effects. Several applications will be presented including 3D-characterization and in situ mechanical testing of polymers, metal alloys, composites and biomaterials. They span multiple length scales from the micro- to the nanoscale and different mechanical testing modes such as compression, indentation and tension.

Metrology and Inspection

Spectroscopic reflectometry is a nondestructive technique widely used to analyze the properties of materials as thin layer thicknesses are used in advanced packaging manufacturing. The technique is based on the propagation of waves into media. If a discontinuity is encountered, a part of its energy is reflected back to the injection point according to the well-known law of reflection. The reflected signal gives useful information about the system and, in particular, thicknesses of thin layers.

3D Crystallographic Imaging Using Laboratory-Based Diffraction Contrast Tomography (DCT)

Traditional X-ray tomography has, for some time, operated under a single absorption-based contrast mechanism. However, in recent years X-ray imaging has experienced a dramatic increase in the range of accessible imaging modalities – extending the classical absorption contrast with e.g. phase contrast, dark-field contrast, fluorescence, diffraction contrast, etc. Common for almost all such new imaging modalities are that they were developed at synchrotron facilities, and then – for some – have since been implemented on laboratory X-ray systems. [1,2]

Sub-80 nm Resolution X-Ray Fluorescence Imaging Spectrometer for Semiconductor Applications

Electron or x-ray excited X-ray fluorescence analysis is a widely deployed technique in various fields such as materials science, semiconductor manufacturing and defect review for thin film characterization. Layer thicknesses with sub nanometer accuracy and elemental composition to below a weight percent can be measured. With electron beam instruments such as SEMs, spatially resolved fluorescence maps are obtained by raster scanning a finely focused electron beam using energy or wavelength dispersive spectrometers (EDS/WDS) to collect elemental distribution and concentration information. The spatial resolution for these maps is fundamentally limited for thick (>1um) samples by the electron interaction volume to the order of one micrometer. This restriction can be overcome by the use of high-resolution Fresnel zone plate lenses as x-ray imaging optics. Based on this concept we have designed an x-ray fluorescence imaging spectrometer which combines the elemental identification capabilities of a spectrometer with the high spatial resolution (sub-80nm) of zone plate imaging optics. Such a spectroscopic imaging system can potentially be employed advantageously in many semiconductor applications. As a first application we demonstrate sub-surface imaging of copper interconnects and identification of manufacturing problems and failures.

Zone plate lens for 10 nm resolution X-ray imaging

We will discuss some exciting possibilities of some synchrotron-based x-ray imaging techniques, including high spatial resolution sub-10 nm resolution and spectromicroscopy capable of chemical state mapping and elemental specific imaging at high spatial resolution. We will also present the development of zone plate lenses for coherent hard x-ray applications.