14 research outputs found
Using Grazing Incidence Small-Angle X-Ray Scattering (GISAXS) for Semiconductor Nanometrology and Defect Quantification
Hintergrund:
Die Entwicklung von Nanotechnologien und insbesondere integrierten Schaltkreisen beruht auf dem Verständnis von Struktur und Funktion auf der Nanoskala, wofür exakte Messungen erforderlich sind.
Kleinwinkel-Röntgenstreuung unter streifendem Einfall (GISAXS) ist eine Methode zur schnellen, berührungs- und zerstörungsfreien dimensionellen Messung von nanostrukturierten Oberflächen.
Ziele:
Es soll die Möglichkeit untersucht werden, die zunehmend komplexeren Proben aus Wissenschaft und Industrie mit Hilfe von GISAXS präzise zu vermessen.
Ein weiteres Ziel ist es, Messtargets aus der Halbleiter-Qualitätskontrolle mit einer Größe von ca. 40x40 µm² zu messen, deren Signal typischerweise nicht zugänglich ist, weil ein Bereich von ca. 1x20 mm² auf einmal beleuchtet wird.
Methoden:
Synchrotron-basierte GISAXS-Messungen verschiedener Proben werden mit Hilfe einer Fourier-Konstruktion, der "distorted wave Born approximation" und einem Maxwell-Gleichungs-Löser basierend auf finiten Elementen analysiert.
Ergebnisse:
Aus GISAXS-Messungen kann die Linienform von Gittern mit einer Periode von 32 nm rekonstruiert werden und sie weicht weniger als 2 nm von Referenzmessungen ab.
Eine sorgfältige Bayes'sche Unsicherheitsanalyse zeigt jedoch, dass wichtige dimensionelle Parameter innerhalb der Unsicherheiten nicht übereinstimmen.
Für die Messung von kleinen Gittertargets entwerfe ich ein neuartiges Probendesign, bei dem das Target in Bezug auf die umgebenden Strukturen gedreht wird, und stelle fest, dass dadurch parasitäre Streuung effizient unterdrückt wird.
Fazit:
GISAXS-Messungen von komplexen Nanostrukturen und kleinen Targets sind möglich, jedoch würde GISAXS enorm von effizienteren Simulationsmethoden profitieren, die alle relevanten Effekte wie Rauhigkeit und Randeffekte einbeziehen.
Hier gibt es vielversprechende theoretische Ansätze, so dass GISAXS eine zusätzliche Methode für die Halbleiter-Qualitätskontrolle werden könnte.Background.
The development of nanotechnology such as integrated circuits relies on an understanding of structure and function at the nanoscale, for which reliable and exact measurements are needed.
Grazing-incidence small angle X-ray scattering (GISAXS) is a versatile method for the fast, contactless and destruction-free measurement of sizes and shapes of nanostructures on surfaces.
Aims.
A goal of this work is to investigate the possibility of precisely measuring the increasingly complex samples produced in science and industry using GISAXS.
A second objective is to measure targets used in semiconductor quality control with a size of approx. 40x40 µm², whose signal is typically not accessible because an area of approx. 1x20 mm² is illuminated at once.
Methods.
I take synchrotron-based GISAXS measurements and analyze them using reciprocal space construction, the distorted wave born approximation, and a solver for Maxwell's equations based on finite elements.
Results.
I find that the line shape of gratings with a period of 32 nm can be reconstructed from GISAXS measurements and the results deviate less than 2 nm from reference measurements;
however, a careful Bayesian uncertainty analysis shows that key dimensional parameters do not agree within the uncertainties.
For the measurement of small grating targets, I create a novel sample design where the target is rotated with respect to the surrounding structures and find that this efficiently suppresses parasitic scattering.
Conclusions.
I show that GISAXS measurements of complex nanostructures and small targets are possible, and I highlight that further development of GISAXS would benefit tremendously from efficient simulation methods which describe all relevant effects such as roughness and edge effects.
Promising theoretical approaches exist, so that GISAXS has the potential to become an additional method in the toolkit of semiconductor quality control
Grazing Incidence Small Angle X-Ray Scattering (GISAXS) on Small Targets Using Large Beams
GISAXS is often used as a versatile tool for the contactless and
destruction-free investigation of nanostructured surfaces. However, due to the
shallow incidence angles, the footprint of the X-ray beam is significantly
elongated, limiting GISAXS to samples with typical target lengths of several
millimetres. For many potential applications, the production of large target
areas is impractical, and the targets are surrounded by structured areas.
Because the beam footprint is larger than the targets, the surrounding
structures contribute parasitic scattering, burying the target signal. In this
paper, GISAXS measurements of isolated as well as surrounded grating targets in
Si substrates with line lengths from down to
are presented. For the isolated grating targets, the changes in the scattering
patterns due to the reduced target length are explained. For the surrounded
grating targets, the scattering signal of a target grating structure is separated from the
scattering signal of nanostructured
surroundings by producing the target with a different orientation with respect
to the predominant direction of the surrounding structures. The described
technique allows to apply GISAXS, e.g. for characterization of metrology fields
in the semiconductor industry, where up to now it has been considered
impossible to use this method due to the large beam footprint
Reconstructing Detailed Line Profiles of Lamellar Gratings from GISAXS Patterns with a Maxwell Solver
Laterally periodic nanostructures were investigated with grazing incidence
small angle X-ray scattering (GISAXS) by using the diffraction patterns to
reconstruct the surface shape. To model visible light scattering, rigorous
calculations of the near and far field by numerically solving Maxwell's
equations with a finite-element method are well established. The application of
this technique to X-rays is still challenging, due to the discrepancy between
incident wavelength and finite-element size. This drawback vanishes for GISAXS
due to the small angles of incidence, the conical scattering geometry and the
periodicity of the surface structures, which allows a rigorous computation of
the diffraction efficiencies with sufficient numerical precision. To develop
dimensional metrology tools based on GISAXS, lamellar gratings with line widths
down to 55 nm were produced by state-of-the-art e-beam lithography and then
etched into silicon. The high surface sensitivity of GISAXS in conjunction with
a Maxwell solver allows a detailed reconstruction of the grating line shape
also for thick, non-homogeneous substrates. The reconstructed geometrical line
shape models are statistically validated by applying a Markov chain Monte Carlo
(MCMC) sampling technique which reveals that GISAXS is able to reconstruct
critical parameters like the widths of the lines with sub-nm uncertainty
spin-state and metal coordination revealed from resonant inelastic X-ray scattering and electronic structure calculations
The local electronic structure of the cobalt centre-ion of Co(III)
protoporphyrin IX chloride dissolved in dimethyl sulfoxide (DMSO) liquid
solution is studied by resonant inelastic X-ray scattering (RIXS) spectroscopy
at the cobalt L-edge. The resulting cobalt 2p partial-fluorescence-yield (PFY)
X-ray absorption (XA) spectrum, integrated from RIXS spectra, is simulated for
various possible spin-states and coordination of the cobalt centre by using
the newly developed density functional theory/restricted open shell single
excitation configuration interaction (DFT/ROCIS) method. Comparison between
experiment and calculation shows that the cobalt ion (3d6 electronic
configuration) adopts a low-spin state with all six 3d electrons paired, and
the cobalt centre is either 5-coordinated by its natural ligands (one chloride
ion and four nitrogen atoms), or 6-coordinated, when binding to an oxygen atom
of a DMSO solvent molecule. Analysis of the measured RIXS spectra reveals weak
3d–3d electron correlation, and in addition a value of the local HOMO–LUMO gap
at the Co sites is obtained
Interactive animations showing grazing-incidence small-angle X-ray scattering of nanostructured surfaces
Zwei Animationen, die Messungen der Röntgenstreuung von nanostrukturierten Oberflächen unter streifendem Einfall visualisieren.Two animations visualizing measurements of X-ray scattering of nanostructured surfaces under grazing incidence.
Figure S1 shows measurements of the in-plane rotation angle distribution of a sample manufactured using nanoimprint lithography.
Figure S2 shows measurements and theoretical expectation of the scattering of a small grating target surrounded by ordered structures, at a range of azimuthal rotation angles