One-step measurement of micro-periodic structures from single diffraction image

H. Goto; S. Kadoya; M. Michihata; S. Takahashi

doi:10.1117/12.3005530

20 September 2023 One-step measurement of micro-periodic structures from single diffraction image

H. Goto, S. Kadoya, M. Michihata, S. Takahashi

Proceedings Volume 12607, Optical Technology and Measurement for Industrial Applications Conference; 1260708 (2023) https://doi.org/10.1117/12.3005530
Event: Optics and Photonics International Congress, 2023, Yokohama, Japan

Abstract

The significant development of terahertz wave technology requires precise measurement of terahertz optical devices such as diffractive gratings with micrometer-scale periodicity. We propose a new measurement method for fast, robust and precise shape measurement of micro-periodic structures, which can be regarded as a scan-less version of the deflectometry. Whereas the deflectometry demands the scanning of the beam spot in order to collect the tilt angle information from various different position on the sample surface, the proposed method simultaneously obtains it from a single diffraction image, then reconstructs the sample shape based on a light reflection model called ray reflection model. In comparison to the interferometry, the proposed method is principally robust to the mechanical vibration because the diffraction image is hardly affected by the displacement of the sample. The limitation of the proposed method is also discussed, and the mathematical expression of the constraint conditions required for the shape reconstruction is clarified. The numerical experiment based on the electromagnetic simulation with rigorous coupled-wave analysis (RCWA) demonstrates the possible accuracy on the order of 10 nm and the effectiveness of the use of the incoherent light. The physical experiment is also conducted by the constructed optical system, and the fundamental validity of the measurement result of the proposed method is confirmed.

Citation Download Citation

H. Goto, S. Kadoya, M. Michihata, and S. Takahashi "One-step measurement of micro-periodic structures from single diffraction image", Proc. SPIE 12607, Optical Technology and Measurement for Industrial Applications Conference, 1260708 (20 September 2023); https://doi.org/10.1117/12.3005530

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KEYWORDS

Diffraction

Reflection

Image restoration

Deflectometry

Terahertz radiation

Statistical modeling

Diffraction gratings

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