High-Aspect-Ratio Thin-Film Stiffening Structures Made of Atomic-Layer-Deposited Alumina and Its Application to a Scanning Micromirror

This work presents the first high-aspect-ratio alumina stiffening structures, fabricated by combining atomic layer deposition (ALD) of alumina with silicon deep reactive ion etching (Si-DRIE), designed to improve MEMS micromirror devices. By selective etching of an alumina-coated silicon mold, we pr...

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Bibliographic Details
Published in:Journal of microelectromechanical systems 2023-08, Vol.32 (4), p.1-10
Main Authors: Tung, Nguyen Thanh, Saito, Shuhei, Sasaki, Takashi, Greif, Daniel, Parsons, Maxwell F., Holmes, Steve, Hane, Kazuhiro
Format: Article
Language:English
Subjects:
alumina
Aluminum oxide
Atomic layer deposition
Atomic layer epitaxy
Deformation
Diameters
Etching
Fabrication
Fins
freestanding thin film
High aspect ratio
Ions
Micromechanical devices
micromirror
Micromirrors
Reactive ion etching
Silicon
silicon deep reactive ion etching
Stiffening
thin film stiffening structure
Thin films
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Summary:This work presents the first high-aspect-ratio alumina stiffening structures, fabricated by combining atomic layer deposition (ALD) of alumina with silicon deep reactive ion etching (Si-DRIE), designed to improve MEMS micromirror devices. By selective etching of an alumina-coated silicon mold, we produced vertical alumina fins with a depth up to 500 \upmu m and a width down to 0.13 \upmu m, corresponding film-aspect-ratios up to 3800. We applied this stiffening structure to a lightweight MEMS micromirror with 215 \upmu m thickness and 2 mm diameter. We characterized the optical flatness and dynamic deformation of this device, which are quantities of interest for compact image projection systems.
ISSN:1057-7157
1941-0158
DOI:10.1109/JMEMS.2023.3275960