Investigation of measurement data of low-coherence interferometry at tilted surfaces in the 3D spatial frequency domain
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Marco Künne
M. Sc. Marco Künne is a research assistant in the Measurement Technology Group of the University of Kassel, Faculty of Electrical Engineering and Computer Science. He studied Nanoscience at the University of Kassel until 2019. He is working in the research field of high-resolution optical interferometry.
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Sebastian Hagemeier
M. Sc. Sebastian Hagemeier is a research assistant in Measurement Technology Group of University of Kassel, Faculty of Electrical Engineering and Computer Science. His research objects are Multisensor measuring systems for topography sensors, Fiber optic sensors and Coherence scanning interferometry (CSI).
M. Sc. Eireen Käkel is a research assistant in the Technological Electronics Group of the University of Kassel, Faculty of Electrical Engineering and Computer Science. She studied Nanoscience at the University of Kassel until 2019 and is now working in the research field of Nanoimprint technology.
Prof. Hartmut Hillmer studied physics at the Universitiy of Stuttgart (Ph. D. degree in 1989). In 1996 he finished his habilitation in engineering from Technical University of Darmstadt. He was working 10 years at Research Center German Telekom Darmstadt on high-speed semiconductor lasers. In 1991 he was guest scientist at NTT Optoelectronic Laboratories, Japan. Since 1999 he is Professor at the University of Kassel, heading Institute of Nanostructure Technologies and Analytics, Technological Electronics. His main research interests are optical MEMS, optical nanosensors and -actuators and nanotechnology focussing functionalized 3D particles and 3D nanoimprint.
Prof. Peter Lehmann studied physics at the Universities of Münster and Karlsruhe. He reached the Dr.-Ing. degree at the University of Bremen in 1994 and finished his Habilitation in 2002. From 2001 till 2008 he was employed at an industrial manufacturer of measuring instruments, where he coordinated research activities in optical metrology. Since then he is a full professor (W3) and holds the chair in measurement technology at the faculty of electrical engineering and computer science of the University of Kassel, Germany. His research interests relate especially to interferometric methods in optical metrology.
Abstract
The 3D transfer characteristics of interference microscopes and their effect on the interference signals occurring at surface slopes are studied. The interference image stacks acquired during a depth scan are 3D Fourier transformed. This allows a comprehensive frequency domain analysis of the interferograms. The double foil model introduced in a previous publication enables the interpretation of the signal spectra and the underlying transfer behavior of the interferometer using the concept of the Ewald sphere, which is limited by the numerical aperture (NA) of the imaging system. Analysis in the 3D spatial frequency domain directly discloses that the lateral dimensions of the transfer function depend on the axial spatial frequency. In this contribution we investigate measuring objects produced by Nanoimprint-Lithography. The corresponding signal spectra bear information that can be utilized to optimize the subsequent signal processing algorithms. These include envelope and phase evaluation procedures of the interference signals. A narrow bandpass filter is used to actively select certain frequency components in order to improve the robustness of the estimation of the envelope position. Although the shape and width of the envelope are affected, this procedure increases the reliability of the evaluation process and improves the accuracy of the measured topography especially at steeper surface slopes.
Zusammenfassung
In diesem Beitrag werden das 3D-Übertragungsverhalten von Interferenzmikroskopen und dessen Einfluss auf die Eigenschaften von Interferenzsignalen insbesondere an geneigten Oberflächen untersucht. Die aufgenommenen Interferenz-Bilderstapel werden in den 3D-Ortsfrequenzbereich transformiert. Dies ermöglicht eine umfassende Signalanalyse, die durch das in einer vorangegangenen Publikation eingeführte Double Foil Model unterstützt wird. Dieses Modell erlaubt die Interpretation der Signalspektren und des zugrunde liegenden Übertragungsverhaltens des Interferometers. Dabei werden die relevanten Ortsfrequenzanteile durch das Konzept der Ewald-Kugel bestimmt, die durch die numerische Apertur (NA) des Mikroskopobjektivs begrenzt wird. Die 3D Frequenzbereichsanalyse zeigt unmittelbar, dass die laterale Ausdehnung der Übertragungsfunktion von der axialen Ortsfrequenz abhängt In diesem Beitrag werden Messergebnisse von mittels Nanoimprint-Lithographie hergestellten Messobjekten untersucht. Die Charakteristika der zugehörigen Signalspektren können für eine verbesserte Analyse der Einhüllenden und der Phasenlage der während des Tiefenscans gemessenen Signale genutzt werden. Dabei werden die Interferenzsignale zunächst mit einem schmalen Bandpassfilter gefiltert, um die relevanten Signalfrequenzen zu extrahieren. Obwohl sich dabei die Form und Breite der Einhüllenden ändern, wird die Zuverlässigkeit der Topographiebestimmung verbessert. Dies gilt insbesondere für stark geneigte Oberflächenbereiche.
Funding source: Deutsche Forschungsgemeinschaft
Award Identifier / Grant number: LE 992/13-1
Award Identifier / Grant number: HI 763/16-1
Funding statement: The financial support of the Deutsche Forschungsgemeinschaft (DFG, LE 992/13-1, HI 763/16-1) is gratefully acknowledged.
About the authors
M. Sc. Marco Künne is a research assistant in the Measurement Technology Group of the University of Kassel, Faculty of Electrical Engineering and Computer Science. He studied Nanoscience at the University of Kassel until 2019. He is working in the research field of high-resolution optical interferometry.
M. Sc. Sebastian Hagemeier is a research assistant in Measurement Technology Group of University of Kassel, Faculty of Electrical Engineering and Computer Science. His research objects are Multisensor measuring systems for topography sensors, Fiber optic sensors and Coherence scanning interferometry (CSI).
M. Sc. Eireen Käkel is a research assistant in the Technological Electronics Group of the University of Kassel, Faculty of Electrical Engineering and Computer Science. She studied Nanoscience at the University of Kassel until 2019 and is now working in the research field of Nanoimprint technology.
Prof. Hartmut Hillmer studied physics at the Universitiy of Stuttgart (Ph. D. degree in 1989). In 1996 he finished his habilitation in engineering from Technical University of Darmstadt. He was working 10 years at Research Center German Telekom Darmstadt on high-speed semiconductor lasers. In 1991 he was guest scientist at NTT Optoelectronic Laboratories, Japan. Since 1999 he is Professor at the University of Kassel, heading Institute of Nanostructure Technologies and Analytics, Technological Electronics. His main research interests are optical MEMS, optical nanosensors and -actuators and nanotechnology focussing functionalized 3D particles and 3D nanoimprint.
Prof. Peter Lehmann studied physics at the Universities of Münster and Karlsruhe. He reached the Dr.-Ing. degree at the University of Bremen in 1994 and finished his Habilitation in 2002. From 2001 till 2008 he was employed at an industrial manufacturer of measuring instruments, where he coordinated research activities in optical metrology. Since then he is a full professor (W3) and holds the chair in measurement technology at the faculty of electrical engineering and computer science of the University of Kassel, Germany. His research interests relate especially to interferometric methods in optical metrology.
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Articles in the same Issue
- Frontmatter
- Editorial
- XXXV. Messtechnisches Symposium des AHMT
- Beiträge
- Funktionsprinzip und Anwendung der Kraftkompensationsmessmethode für miniaturisierte hydrogelbasierte Sensoren
- Auslegung neuartiger Transferkörper für die Kalibrierung von Massenormalen
- Lamb wave based approach to the determination of acoustic material parameters
- Metrological nanopositioning combined with two-photon direct laser writing
- Investigation of measurement data of low-coherence interferometry at tilted surfaces in the 3D spatial frequency domain
- Erfassung der Schmelzbadfläche mit Korrektur der Perspektive zur Prozessregelung eines Wire and Arc Additive Manufacturing
- Wear volume estimation for a journal bearing dataset
- Scalable multi-distance measurement approach for the optical assessment of tooth-individual shape parameters of large gearings
