John Wall

High resolution X-ray diffraction using a high brilliance source, with rapid data analysis by auto-fitting

Abstract In a production environment in particular, fast data collection and analysis, which are also highly reliable, are desirable. Measurement can be speeded up by increasing the diffracted intensity, thus reducing the time required to measure it reliably. Increased intensity with a smaller beam footprint at the sample have been achieved in a double-crystal diffractometer by the use of a novel ellipsoidal mirror working by total external reflection, positioned before the reference crystal. To optimise the performance of the mirror and provide high brightnesses, an X-ray source with a very small focal spot is required. Such a high brightness source has been made that uses electromagnetic focusing of the electron beam onto the target. Rapid data analysis is achieved by the use of an auto-fitting program that employs a genetic algorithm and the full dynamical theory of X-ray diffraction. Choice of an appropriate error function produces a deep global minimum while the genetic algorithm avoids convergence on local minima. From the model that produces the best fit, samples parameters such as layer thickness and alloy composition are extracted with quantified goodness of fit.

A Novel X‐ray Diffraction and Reflectivity Tool for Front‐End of Line Metrology

High‐resolution X‐ray diffraction (HRXRD) is an established technique for the characterization and metrology of epitaxial thin‐films. However, its use by the silicon semiconductor industry has been limited due to the stringent reliability, spot‐size and throughput requirements for in‐line measurement of product wafers. We have developed a new X‐ray metrology tool (called the JVX 7200) that meets these demands. The tool features a novel HRXRD channel that provides composition, relaxation and thickness information for SiGe and Si:C epitaxial films. It also combines an enhanced X‐ray reflectivity (XRR) channel to provide complementary thickness, density and roughness information on SiGe as well as other front‐end of line (FEOL) films, such as those found in high‐k gate/metal gate (HKMG) stacks. We describe the principles and capabilities of both the HRXRD and XRR channels and provide a comparison with conventional X‐ray systems. Representative data are presented to highlight the capabilities of the new tool.

Innovative x-ray optics for laboratory

We report on recent developments of innovative grazing incidence X-ray optics for laboratory applications. These efforts focus on the developments of grazing incidence micromirrors with ellipsoidal and paraboloidal profiles and apertures well below 1 mm, as well as on the developments of innovative arrangements and approaches such as X-ray collimators based on the Lobster Eye X-ray lenses. The applications of these elements will be indicated and discussed. Moreover, we will discuss the innovative alternative technologies for X-ray optics elements in study and-or under considerations

Rapid high-resolution X-ray diffraction measurement and analysis of MOVPE pHEMT structures using a high-brilliance X-ray source and automatic pattern fitting

A novel micro-focus X-ray tube in combination with a focusing optic that uses total external reflection has been used to enhance the diffracted intensity in a double-crystal experiment, whilst simultaneously reducing the beam footprint on the sample. The increased intensity allows data to be collected more quickly. Advances in auto-fitting using the full dynamical theory of X-ray diffraction mean that sample material parameters can be extracted quickly and objectively, opening the way to automatic data analysis. Both features are attractive for non-destructive quality control of semiconductor device structures, as well as for process development and research purposes.

Microfocusing with grazing incidence x-ray micromirrors

Grazing incidence micromirrors of ellipsoidal or parabolic shape with apertures below 1 mm have numerous potential applications in many areas of applied physics, molecular biology and material research. One of the most important applications of such optics is in its combination with microfocus x-ray generator. Extremely intense collimated or focused high-quality x-ray beams from tabletop equipment can be obtained in this way. It is shown that though developed primarily for macromolecular crystallography, this combination gave excellent results also in other fields of science and technology. Computer ray-tracing and experimental data characterizing mirror and x-ray beam parameters in typical applications are presented.