Hi Lisa How wedded are you to the Au. You could use other metals and etch them using XeF2 gas. Mo etches the fastest, W next, Ta, Ti under certain conditions. Could you switch the Au for one of these metals? David Springer XACTIX, Inc. 2403 Sidney St. Suite 300 Pittsburgh, PA 15203 Tel: 412 381 3195 Fax: 412 381 1136 Email: davids@xactix.com > 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