Hello. Are these gold pads electrically isolated? Maybe some charge is accumulated on the pads during RIE etching and suddenly discharges. This can result in some high current for a short moment as well as some local heating. As it might alter resist chemistry in an unpredictable way, both can affect/inhibit solubility of the positive tone resist in solvents. Best regards, Norbert Nodes E-Mail: n.nodes@evgroup.com, www.EVGroup.com -----Original Message----- From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org] On Behalf Of Zotl Ernst Sent: Mittwoch, 09. Jänner 2008 15:50 To: mems-talk@memsnet.org Subject: [mems-talk] Dry etching of polyimide with PR mask Dear all, I have a problem when dry etching polyimide with a resist (S1813) mask: After stripping the resist with MEK it seems that some crosslinked resist covers part of the PI. This problem is especially visible around pads (gold) which are etched free (seems like the crosslinked resist is clinging to the PI or resist sidewall). We run this etch on an RIE tool with 300W, 100 sccm O2 and a pressure of 150 mTorr. I had some success in avoiding this kind of residue by mixing the O2 with 20% CF4, reducing the power and increasing the pressure to about 250 mTorr, but this dramatically affects uniformity, with very slow etch rate in the center and high etchrate on the edge of the tool. I would be glad if anyone has some hints how to avoid this problem.