Comparative analysis of fabrication techniques for sensing windows on silicon nitride waveguide platforms

Jakob Wilhelm Hinum-Wagner; Samuel Marko Hoermann; Gandolf Feigl; Christoph Schmidt; Deborah Morecroft; Jochen Kraft; Alexander Bergmann

doi:10.1117/12.3008895

18 June 2024 Comparative analysis of fabrication techniques for sensing windows on silicon nitride waveguide platforms

Jakob Wilhelm Hinum-Wagner, Samuel Marko Hoermann, Gandolf Feigl, Christoph Schmidt, Deborah Morecroft, Jochen Kraft, Alexander Bergmann

Author Affiliations +

Proceedings Volume 13012, Integrated Photonics Platforms III; 130120N (2024) https://doi.org/10.1117/12.3008895
Event: SPIE Photonics Europe, 2024, Strasbourg, France

Conference Poster

Abstract

This study provides an in-depth evaluation of two fundamental techniques for fabricating sensing windows on silicon nitride platforms: a traditional etching strategy using reactive ion etching (RIE) combined with wet etching, and a lift-off-based process in which the top cladding material is deposited onto a suitable resist which is subsequently stripped of the distinct sensing waveguides. The analysis, based on a side-by-side comparison, meticulously examines the effectiveness of these methods. Key evaluation metrics include propagation and bending loss in the sensing windows, process robustness, and uniformity of critical dimensions and heights across the wafer. This will provide a comprehensive understanding of the strengths, weaknesses, and potential application limitations of each technique. An integral part of the study is the careful revision of the waveguide material stack to address specific challenges and applications. This precise tuning and adaptation of the material stack serve as a proxy for the demands likely to be encountered in real-world applications. The conservative etching technique has the advantage that it can be easily combined with subsequent facet etching processes for edge coupling approaches. Conversely, the lift-off resist based approach, despite its relative complexity and sensitivity to high-temperature deposition on the resist, reduces the negative impact of the process on surface roughness and sidewall angles. The knowledge gained from this research provides valuable guidance in the selection of appropriate fabrication techniques for specific silicon nitride sensor applications to increase the robustness of the processing steps for potential mass production stability.

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

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Jakob Wilhelm Hinum-Wagner, Samuel Marko Hoermann, Gandolf Feigl, Christoph Schmidt, Deborah Morecroft, Jochen Kraft, and Alexander Bergmann "Comparative analysis of fabrication techniques for sensing windows on silicon nitride waveguide platforms", Proc. SPIE 13012, Integrated Photonics Platforms III, 130120N (18 June 2024); https://doi.org/10.1117/12.3008895

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