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Proceedings Paper

Very deep fused silica etching
Author(s): Ingo Steingoetter; Axel Grosse; Henning Fouckhardt
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Paper Abstract

Fabrication processes for wet chemical and dry etching of hollow capillary leaky optical waveguides in high-purity fused silica for extended path cells for improved optical detection in analytical chemistry are described. We focus on microstructures with etch depths on the order of 80 μm. Special attention is paid to the preparation of the etch masks for the two different etch technologies. The fused silica wet chemical etching technique uses buffered hydrofluoric acid with ultrasonic agitation achieving etch rates > 100 nm/min. We succeeded in developing an etch process based on a single-layer photoresist (AZ 5214E, Clariant Corp.) soft mask, which gives excellent results due to special adhesion promotion and a photoresist hardening cycle after the developing step. This procedure allows for the production of channels of nearly semi-cylindrical profiles with etch depths of up to 87 μm. For the dry etch process a ~10 μm thick Ni layer is used as a hard mask realized with electroplating and a thick photoresist. The etch process is performed in an ECR (Electron Cyclotron Resonance) chamber using CF4 gas. The resulting etch rate for fused silica is about 138 nm/min. Etch depths of (accidentally also) 87 μm are achieved.

Paper Details

Date Published: 17 January 2003
PDF: 10 pages
Proc. SPIE 4984, Micromachining Technology for Micro-Optics and Nano-Optics, (17 January 2003); doi: 10.1117/12.477833
Show Author Affiliations
Ingo Steingoetter, Univ. of Kaiserslautern (Germany)
Axel Grosse, Univ. of Kaiserslautern (Germany)
Henning Fouckhardt, Univ. of Kaiserslautern (Germany)

Published in SPIE Proceedings Vol. 4984:
Micromachining Technology for Micro-Optics and Nano-Optics
Eric G. Johnson, Editor(s)

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