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Etching Copper, Silicon and Aluminum without etching Aluminum Oxide

I am creating a 4 layered arrangement: a silicon wafer, sputtered and then electroplated with copper, then sputtered with aluminum. The Al is then anodized to form Aluminum oxide. Once I have the oxide, I want to etch away everything else.

ferric chloride ⇦this on eBay or Amazon [affil links] can be used to etch Cu and Al, and Potassium Hydroxide can etch the Si, but will either of these harm the Aluminum oxide layer? Are there better alternatives that either cause less harm to the oxide or that can etch away all three materials in one step?

Elliot Jenner
Student - Pittsburgh, Pennsylvania, USA
July 17, 2009

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July 23, 2009

Hi,

Potassium Hydroxide will etch away aluminium oxide. We make nanowires via aluminium oxide membranes, and to free the wires we use KOH to etch the alumina membranes.

Eric

Eric Lewandowski
- Massachusetts

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Use Ammonium Bifluoride for the silicon.

For the pH you'd be at, and at room temp, the aluminum oxide should be safe.

Robert H Kinner
- Toledo, OH, United States
July 29, 2009