If what you really need is an adhesion layer for SU-8 and Au without resorting to Ti or Cr, you should look at "Investigation of the bond strength between the photo-sensitive polymer SU-8 and gold" where Nordström et al report using 4-aminothiolphenol (4-ATP) as a good adhesion layer for SU-8/Au. In short, the amine on 4-ATP reacts with the SU-8's epoxy, and the thiol bonds to the Au. They also list a few other iterations that they had luck with. It's a good, comprehensive paper on the subject. The link is here: http://www.sciencedirect.com/science/article/B6V0W- 4F5S6C5-7/2/e59903c5e0903d82c14a43c5cbb36c38 Regarding your process overall though: 1) With the Cr/Ti adhesion layers, you only need 10 - 20 nm for good adhesion. This should take about 5 minutes (at most) on most equipment (evaporation or sputtering). I don't think this should really be a problem. 2) Regarding omnicoat, don't use this if you want to make a "sandwich." Unless your Au layer is unpatterned, it will give you issues when you try to adhere SU-8 to SU-8. 3) Au adhesion on SU-8 isn't great, but if you're careful you can still pattern it (just be sure to build in a margin for undercutting). And, if you have it in a "sandwich," it should be secure enough in most cases. I honestly doubt you'll need an adhesion layer at all. - Kevin Nichols ********************************* Kevin Paul Nichols Mesoscale Chemical Systems MESA+ Institute for Nanotechnology University of Twente Postbus 217 7500 AE Enschede The Netherlands Office: +31 (0)53 489 30 71 Mobile: +31 (0)6 49 312 471 Fax : +31 (0)53 489 35 95 Email : k.p.nichols@utwente.nl On Feb 26, 2007, at 3:39 AM, Yue Mun Pun, Jeffrey wrote: > Hi, > In building my MEMS device, I need to create a sandwich layer of SU8 > (2050)-Gold-SU8(2050). The Gold layer functions as a conductor. I > have been trying to thermally evaporate either Chromium and/or > Titanium to create an adhesion layer for Gold on SU-8, but the > evaporation rates are low. > Does anybody know if Gold adheres well to SU-8 2050 so I can do > without an adhesion layer? Alternatively, I am considering > switching to using Omnicoat as an adhesion layer for Gold on SU-8 > 2050 instead.