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Light Assisted Electrochemical Etching - Very High Aspect Ratio Silicon Etching

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	Fig. 1: An angled close up of the etched region showing the density of the holes and the hole profile. The holes are on a 12 um pitch. Fig. 2: A side profile showing the etch uniformity of the process. The wafer thickness is 490 to 510um while the etch is 460 to 448 um.

Applications such as optoelectronics, micro-optics, energy conversion, environmental monitoring, microelectronics, wafer technology, and biotechnology can require a high density of through wafer vias. While state of the art DRIE can reach an aspect ratio of 20:1, this can be too small for some applications.

Micralyne has been able to develop a manufacturing process for very high aspect ratio silicon wet etching through a technique called Light Assisted Electrochemical Etching (LA-ECE). LA-ECE was developed in the early 1990's by groups led by Canham (UK) and Lehmann (Germany) as a means to produce highly porous silicon. This technique allows Micralyne to produce a highly porous silicon wafer with aspect ratios of 60:1 (depth:width).

This process uses an HF solution, an applied voltage and light source to form the holes in the silicon wafer. This process also requires n-type silicon wafers. In order to form these holes, Micralyne is able control the 8-10 variables that can affect the quality of this etch; we routinely get high quality etches that are more than 450 um deep. These holes can be used to produce various types of through wafer vias (fluidic, metal, oxide, etc.).

Please contact Dr. Steve Jakeway should you require any additional information sjakeway@micralyne.com.

- By Dr. Steve Jakeway -

email: sjakeway@micralyne.com
web: www.micralyne.com

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