Precise thickness measurement and comparison of step-shaped microfluidic channel mold using optical interferometry

Jungjae Park; Jaeseok Bae; Jonghan Jin

doi:10.1117/12.2525970

21 June 2019 Precise thickness measurement and comparison of step-shaped microfluidic channel mold using optical interferometry

Jungjae Park, Jaeseok Bae, Jonghan Jin

Author Affiliations +

Proceedings Volume 11056, Optical Measurement Systems for Industrial Inspection XI; 110561R (2019) https://doi.org/10.1117/12.2525970
Event: SPIE Optical Metrology, 2019, Munich, Germany

Abstract

Optical interferometry is one of the suitable methods which can be used to measure the physical thicknesses of microscale structures because this approach can measure optical path differences accurately with a non-contact method. In this paper, on the basis of the simultaneous measurement of the physical thickness and refractive index of an optically transparent plane-parallel plate, a spectral-domain interferometer capable of measuring the physical thickness and refractive index of separate layers in a step-shaped structure with two layers was proposed and realized. For a feasibility test, a microfluidic channel mold with two layers was selected as a sample. For verification of the measured thickness in a double-layered region, a contact-type surface profilometer equipped with laser interferometers on the x-y-z axes was used for a thickness comparison. However, it is never simple to compare measured thicknesses due to positioning errors and the different measuring sizes of each method. For these reasons, the corresponding thickness value was defined as an offset between height values at center points of the single-layered and double-layered region in a specific area of 5 mm × 5 mm. For an accurate determination of the offset, the slopes of the surface profile were removed. The assumption that the surface profile of the bottom layer in the double-layered region is very flat was applied to calculate the thickness from the measured surface profile, and this assumption was checked as to whether it is acceptable or not in this study. In conclusion, the physical thicknesses according to a surface profilometer and by the proposed method were determined to be 106.332 μm and 106.304 μm, respectively, in good agreement within the respective uncertainty values.

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Jungjae Park, Jaeseok Bae, and Jonghan Jin "Precise thickness measurement and comparison of step-shaped microfluidic channel mold using optical interferometry", Proc. SPIE 11056, Optical Measurement Systems for Industrial Inspection XI, 110561R (21 June 2019); https://doi.org/10.1117/12.2525970

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