Wet-etching of structures with straight facets and adjustable taper into glass substrates

Lab on a Chip
Nikola PekasDavid Juncker

Abstract

Wet etching of glass by hydrofluoric acid is widely used in microfabrication, but is limited by the isotropic nature of the process that leads to rounded sidewalls and a 90 degrees angle between the etch front and the surface of the substrate. For many applications such as microvalving, or for further processing such as spin-coating, well controlled, gently sloping sidewalls are often preferred. Here, we present a new approach for forming straight facets and for adjusting the sidewall angle in wet-etched glass substrates by controlling the lateral dissolution of an etch mask during etching. The etch mask comprises a Ti-Au bilayer where Au serves to protect the Ti. During isotropic etching of glass by HF the Ti layer is etched away laterally at the same time, which leads to straight, gently sloping sidewalls. We introduce two methods for controlling the sidewall angle. The first one is based on adjusting the thickness of Ti which controls the lateral etch rate, and thus the angle; the thinner the Ti, the slower its lateral etch rate and the steeper the angle in the etched glass. The second method involves a cathodic bias applied to the Ti-Au etch mask which again regulates the dissolution rate of Ti; the more negative the bias t...Continue Reading

References

Feb 8, 2003·Proceedings of the National Academy of Sciences of the United States of America·Chihchen ChenAlbert Folch
Jul 22, 2005·Langmuir : the ACS Journal of Surfaces and Colloids·Rohit JindalSteven M Cramer

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Citations

Jun 5, 2012·Biomicrofluidics·Ciprian IliescuSami Franssila
May 18, 2016·Scientific Reports·Letícia S ShiromaRenato S Lima
Oct 15, 2010·Microscopy Research and Technique·Kai ZhangBianxiao Cui

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