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Proceedings Paper

In-situ optical monitoring of silicon membrane etching
Author(s): Franck Chollet; Ooi Giap Hwai
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Paper Abstract

We present a simple yet efficient technique to obtain membrane with precise thickness by the etching of silicon in anisotropic etchant. This technique uses a mechanical holder to protect the front side of the wafer and a light signal to monitor from a distance the thickness of a reference hole in the etched wafer. The original feature in our set-up is that we measure the absorption of the light in two different bands of wavelength, one where the silicon is highly absorbant and the other where it is not, to improve the robustness of the measurement. This principle allows for effectively compensating for the fluctuation in the light source intensity, and provide real-time information on the membrane thickness, removing the incertitude inherent in the usual timed etch. We present the application of this technique to the manufacturing of thick single-crystal stiffener used to prevent the warp of stacked thin films presenting a gradient of stress.

Paper Details

Date Published: 28 December 2005
PDF: 8 pages
Proc. SPIE 6037, Device and Process Technologies for Microelectronics, MEMS, and Photonics IV, 60370B (28 December 2005);
Show Author Affiliations
Franck Chollet, Nanyang Technological Univ. (Singapore)
Ooi Giap Hwai, Nanyang Technological Univ. (Singapore)

Published in SPIE Proceedings Vol. 6037:
Device and Process Technologies for Microelectronics, MEMS, and Photonics IV
Jung-Chih Chiao; Andrew S. Dzurak; Chennupati Jagadish; David V. Thiel, Editor(s)

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