Hello Dr. Walsh, Yes, using EDP to post-process CMOS fabricated chips was my Ph.D., work at University of Alberta, Canada from 1986-1990. I wrote my doctoral thesis on that. One of the device which I built during that time was heater substrates for flow sensors and that was later converted to a thermal pixel for IR flat panel display. Initially we used the recipe given in Dr. Petersen's paper to prepare the EDP and that infact attacked the Aluminum on the cmos chips. Later I found out that TRANSENE was supplying EDP under the trade name "Silicon Preferential Etchant PSE 100". In the data sheets they had indicated Al as a mask for that etchant. We started buying that and that gave very good results for a while. Later we found the EDP started attacking Al. We called transene and wanted to find out what other chemicals they are adding other than EDP to their mixture. We never got any good leads. Two months later Transene removed the Al as a mask from their label. By then we started to tinker around adding Al to EDP in the form of Al-OH so that the solution is reasonably saturated with Al. That technique is not that stable. Also, we found out that the silicon content in the Al on CMOS chips makes a lot of difference on how long Al will stay during EDP etching. So we decided to do an electroless plating on the exposed Al pads with Nickel and Gold before we do the EDP etching. If you can add Al-OH and also adjust the pyrazene content in EDP, then you can actually get a mixture that doesn't attack Aluminum. This is only good for pure aluminum. Each CMOS vendor uses different Aluminum alloy for metallization. So you cannot get consistent results, unless you have lot of time to play with EDP preparation. Thats why we decided to go for electroless plating. Sorry for a lengthy answer, hope it clarifies your question. If you need more information, please do not hesitate to contact me. Yours sincerely Ash Parameswaran School of Engineering Science Simon Fraser University Burnaby, BC Canada V5A 1S6. Tel: (604) 291-4971 fax: (604) 291-4951