Hi Everyone,

Thank you for your input!  To answer a few of your questions:

-Dave L:  We explored potassium cyanide, but we will not be allowed to
use it at our facility due to safety concerns.

-Andy:  A sputtering or dry etching process remains a possibility.

-Kevin:  We can't be flexible on the Al for the particular device that
we are making (the device itself is Al, and the Au is just a sacrificial
layer).  We tried Cr as the sacrificial layer over Al but found that
during/after ICP RIE, some sort of interaction happened between the Al
and the Cr which caused defects in the edges of the Al (possibly a
galvanic effect?).

-David R.:  Thank you for the suggestion of electrochemical etching in
sulfuric acid.  I will discuss this with my collaborators.

We found one paper (Su et al. 2008, Maximizing Selectivity During
Wet-Chemical Gold Etching) in which the authors experimented with
various compounds added to standard Au etchant.  They found that
citrates and phosphates may improve selectivity.  We are thinking of
trying this as well.

Thanks again for your suggestions!

Lisa