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Proceedings Paper

Real-time monitoring of thickness of silicon membrane during wet etching using a novel surface acoustic wave sensor
Author(s): Chi-Yuan Lee; Tsung-Tsong Wu; Yung-Yu Chen; Ying-Chou Cheng; Wen-Jong Chen; Shih-Yung Pao; Pei-Zen Chang; Ping-Hei Chen; Kai-Hsiang Yen; Fu-Yuan Xiao
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Paper Abstract

This study presents a novel method based on the surface acoustic wave (SAW) sensor, for monitoring the thickness of a silicon membrane in real time during wet etching. Similar to accelerometers and pressure sensors, some micro-electro-mechanical systems (MEMS) devices require the thickness of silicon membranes to be known precisely. Precisely controlling the thickness of a silicon membrane during wet etching is important, because the thickness strongly affects post-processing and device performance. Moreover, the proposed surface acoustic wave sensor allows the thickness of a silicon membrane to be monitored from a few μm to hundreds of μm in situ, which depends on the periodicity of interdigital transducers (IDT). A novel method, which differs from any in previous work on etch-stop techniques, is developed in-situ for monitoring the thickness of a silicon membrane during wet etching. In summary, the proposed method for measuring the thickness of a silicon membrane in real time, is highly accurate; is simple to implement, and can be mass-produced. This work also describes the principles of the method used, detailed process flows, the method of taking measurements and the simulated and experimental results. The theoretical and measured values differ by an error of less than 2.50μm, so the results closely agree with each other.

Paper Details

Date Published: 16 August 2004
PDF: 12 pages
Proc. SPIE 5455, MEMS, MOEMS, and Micromachining, (16 August 2004); doi: 10.1117/12.544959
Show Author Affiliations
Chi-Yuan Lee, National Taiwan Univ. (Taiwan)
Tsung-Tsong Wu, National Taiwan Univ. (Taiwan)
Yung-Yu Chen, National Taiwan Univ. (Taiwan)
Ying-Chou Cheng, National Taiwan Univ. (Taiwan)
Wen-Jong Chen, National Taiwan Univ. (Taiwan)
Shih-Yung Pao, National Taiwan Univ. (Taiwan)
Pei-Zen Chang, National Taiwan Univ. (Taiwan)
Ping-Hei Chen, National Taiwan Univ. (Taiwan)
Kai-Hsiang Yen, National Taiwan Univ. (Taiwan)
Fu-Yuan Xiao, National Taiwan Univ. (Taiwan)

Published in SPIE Proceedings Vol. 5455:
MEMS, MOEMS, and Micromachining
Hakan Urey; Ayman El-Fatatry, Editor(s)

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