J. Eur. Opt. Society-Rapid Publ. 2026, 22, 36 Ó The Author( s), published by EDP Sciences, 2026 https:// doi. org / 10.1051 / jeos / 2026028 Available online at: https:// jeos. edpsciences. org
Journal of the European Optical Society-Rapid Publications
RESEARCH ARTICLE
Flexible calibration and alignment tool for scanning beam interference lithography systems based on aerial imaging
Kevin Treptow 1,*
, Josias Rühle 2, Christof Pruß 1, Ingo Ortlepp 3, Tobias Haist 1, Oliver Sawodny 2, Eberhard Manske 3, Thomas Kissinger 3, and Stephan Reichelt 1
1 |
Institute of Applied Optics( ITO), University of Stuttgart, Stuttgart, Germany |
2 |
Institute for System Dynamics, University of Stuttgart, Stuttgart, Germany |
3 |
Institute of Process Measurement and Sensor Technology, Technische Universität Ilmenau, Ilmenau, Germany |
Received 29 January 2026 / Accepted 17 March 2026
Abstract. Calibration and alignment of scanning beam interference lithography( SBIL) systems remain major challenges due to the high sensitivity of the interference pattern to multiple system degrees of freedom. In this work, a fringe observation system is presented as a quantitative tool for the calibration and alignment of SBIL writing heads. It consists of a compact microscope mounted on a nanopositioning machine, enabling direct imaging of the aerial writing pattern onto a camera. Fringe motion is quantified using the carrier-frequency method. Based on this approach, a comprehensive calibration protocol was developed to characterize key degrees of freedom, including fringe orientation, fringe period, pattern tilt, and positioning errors during the scan-and-stitch process. The writing pattern was aligned parallel to the scan direction to ensure optimal exposure contrast. The fringe period and pattern tilts were determined with nanometer precision, and scan-andstitch positioning errors were evaluated along a classical SBIL trajectory. Finally, the effectiveness of the calibration procedure was validated by exposure tests in positive photo resist, demonstrating high structural quality and excellent agreement between structures and optical measurements. The presented fringe observation system provides a powerful tool for SBIL calibration and forms the basis for future implementation of insitu feedback and compensation strategies to further improve fabrication accuracy.
Keywords: Laser lithography, Scanning beam interference lithography, Gratings, Diffractive elements, Carrier-frequency interferometry.
1 Introduction
Scanning beam interference lithography( SBIL) is a highprecision patterning technique. It produces periodic grating structures by scanning a substrate through the interference field of two coherent laser beams. SBIL was first introduced by the Massachusetts Institute of Technology in context of the“ Nanoruler” [ 1 ]. The achievable pattern quality, including period accuracy and uniformity, is fundamentally determined by the optical alignment performed before the scan process. This initial setup requires careful calibration of fringe pattern orientation, period, wavefront overlap, and fringe pattern tilt. Misalignment in these parameters introduces systematic errors, i. e. dosis contrast errors, that deteriorates directly the fabricated structures, making alignment one of the most critical steps in SBIL operation.
* Corresponding author: kevin. treptow @ ito. uni-stuttgart. de
The orientation of the interference fringes is governed by the relative propagation directions of the interfering beams. For larger exposure patterns, even microradianscale angular deviations lead to a measurable rotation of the fringe field, which translates into systematic contrast losses during long-range scanning. An automated beam alignment procedure for SBIL, enabling microradian-level control of the interfering beams and establishing the foundational methodology for modern SBIL alignment has been developed in other previous works [ 2, 3 ]. Complementary alignment approaches employed in high-accuracy interference lithography utilize interferometric referencing and Fourier imaging to measure and correct orientation deviations. Another approach is referencing the interference field against calibrated gratings. This enables angular alignment precision, reduces orientation drift and improves pattern fidelity [ 4 ]. The fringe period is defined by the interference angle and the laser wavelength, and it must be realized with high accuracy for applications such as diffraction gratings or encoder standards. Nanometer-level period accuracy in
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