Through Silicon MEMS Inspection with a Near-Infrared Laser Scanning Setup

Rodrigues, Manuel J. L. F.; Garcia, Inês S.; Santos, Joana D.; Mota, Filipa C.; Alves, Filipe S.; Aguiam, Diogo E.

doi:10.3390/s25154627

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Open AccessArticle

Through Silicon MEMS Inspection with a Near-Infrared Laser Scanning Setup

by

Manuel J. L. F. Rodrigues

^*

,

Inês S. Garcia

,

Joana D. Santos

,

Filipa C. Mota

,

Filipe S. Alves

and

Diogo E. Aguiam

^*

International Iberian Nanotechnology Laboratory, Avenida Mestre José Veiga, 4715-330 Braga, Portugal

^*

Authors to whom correspondence should be addressed.

Sensors 2025, 25(15), 4627; https://doi.org/10.3390/s25154627

Submission received: 4 June 2025 / Revised: 15 July 2025 / Accepted: 22 July 2025 / Published: 25 July 2025

(This article belongs to the Special Issue Optical Sensors for Industry Applications)

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Abstract

The inspection of encapsulated MEMS devices typically relies on destructive methods which compromise the structural integrity of samples. In this work, we present the concept and preliminary experimental validation of a laser scanning setup to non-destructively inspect silicon-encapsulated microstructures by measuring small variations of transmitted light intensity in the near-infrared spectrum. This method does not require any particular sample preparation or damage, and it is based on the higher degree of transparency of silicon in the near-infrared and the transmission contrast resulting from the Fresnel reflections observed at the interfaces between the different materials of the MEMS device layers. We characterise the small feature resolving performance of the laser scanning setup using standard targets, and experimentally demonstrate the inspection of a MEMS latching device enclosed within silicon covers, comparing the contrast measurements with theoretical predictions.

Keywords: MEMS; IR Inspection tool; nanometrology

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MDPI and ACS Style

Rodrigues, M.J.L.F.; Garcia, I.S.; Santos, J.D.; Mota, F.C.; Alves, F.S.; Aguiam, D.E. Through Silicon MEMS Inspection with a Near-Infrared Laser Scanning Setup. Sensors 2025, 25, 4627. https://doi.org/10.3390/s25154627

AMA Style

Rodrigues MJLF, Garcia IS, Santos JD, Mota FC, Alves FS, Aguiam DE. Through Silicon MEMS Inspection with a Near-Infrared Laser Scanning Setup. Sensors. 2025; 25(15):4627. https://doi.org/10.3390/s25154627

Chicago/Turabian Style

Rodrigues, Manuel J. L. F., Inês S. Garcia, Joana D. Santos, Filipa C. Mota, Filipe S. Alves, and Diogo E. Aguiam. 2025. "Through Silicon MEMS Inspection with a Near-Infrared Laser Scanning Setup" Sensors 25, no. 15: 4627. https://doi.org/10.3390/s25154627

APA Style

Rodrigues, M. J. L. F., Garcia, I. S., Santos, J. D., Mota, F. C., Alves, F. S., & Aguiam, D. E. (2025). Through Silicon MEMS Inspection with a Near-Infrared Laser Scanning Setup. Sensors, 25(15), 4627. https://doi.org/10.3390/s25154627

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Through Silicon MEMS Inspection with a Near-Infrared Laser Scanning Setup

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