Simultaneous Dimensional and Analytical Characterization of Ordered Nanostructures

Abstract

The spatial and compositional complexity of 3D structures employed in today's nanotechnologies has developed to a level at which the requirements for process development and control can no longer fully be met by existing metrology techniques. For instance, buried parts in stratified nanostructures, which are often crucial for device functionality, can only be probed in a destructive manner in few locations as many existing nondestructive techniques only probe the objects surfaces. Here, it is demonstrated that grazing exit X‐ray fluorescence can simultaneously characterize an ensemble of regularly ordered nanostructures simultaneously with respect to their dimensional properties and their elemental composition. This technique is nondestructive and compatible to typically sized test fields, allowing the same array of structures to be studied by other techniques. For crucial parameters, the technique provides sub‐nm discrimination capabilities and it does not require access‐limited large‐scale research facilities as it is compatible to laboratory‐scale instrumentation.

Challenges of grazing emission X-ray fluorescence (GEXRF) for the characterization of advanced nanostructured surfaces

“…This is achieved by tuning the incoming photon energy above the corresponding absorption edges of the involved materials (Ti, Cr), in contrast to methods that use an energy-dispersive detector. 17 The nanostructures are more complex than what can be described in terms of simple geometric shapes such as rectangles or trapezoids. A parametrization of such a line shape is also not trivial and would have to be oriented more to the process variations to be expected in production.…”

“…The field inside the TiO 2 and Cr is extracted, and the square of the absolute value, which is the field intensity, is compared to the experimental data from the area detector because it is proportional to the emitted fluorescence of the material. 17,38 The principle of microscopic reversibility allows using GEXRF calculation tools developed for GIXRF by setting the photon energy of interest to that of the fluorescence photons instead of that of the incident photons. 13 The emitted fluorescence photon is considered an incoming photon with the fluorescence energy of the titanium K α line and the direction of the area detector pixel.…”

“…These effects have recently been used to characterize structured surfaces as well. 17 A significant advantage of this method is that buried structures can also be measured due to the penetration depth of the X-rays, and the beam size alone determines the probed area in its lateral dimensions. This also enables the scanning of laterally inhomogeneous samples.…”

Traceable Characterization of Nanomaterials by X-ray Spectrometry Using Calibrated Instrumentation

“…The GEXRF approaches have been successfully explored for more than two decades at various large-scale facilities and in academic laboratories [75][76][77][78][79][80][81], in particular regarding the characterization of nanolayered systems. To complement angular GIXRF studies [22,72] and related reconstruction works on nanostructures [73], GEXRF also allows for the scanning-free detection of the angular distribution of fluorescence radiation emitted by a nanostructure using position-sensitive detectors such as CCDs or CMOS devices [82].…”

Reporting SERS enhancement factor: molecular surface coverage standards by grazing-incidence X-ray fluorescence.

“…We propose synchrotron-radiation-based reference-free X-ray fluorescence (RF-XRF), under grazing incidence conditions (GIXRF) [13], as schematized in figure 1a, to quantify the surface density of a molecular species adsorbed on the surface of a plasmonic metal by identifying a distinguishable target element with atomic number Z higher than 9 in the molecular structure. Indeed, the target element needs to have a detectable characteristic X-ray fluorescence line with well-known atomic fundamental parameters (FPs) and it should be different from the typical constituents of the molecules (C, N, O).…”