Hi Manjula, You can use a low pressure chemical vapor deposition (LPCVD) nitride or Au/Cr for deep and long KOH etching. Regards, Mahdi Bagheri manjula ramanwrote: I need some information of some etch mask other than silicon dioxide for KOH etching.I am doing a long duration etching(atleast 5 hrs)and using a thick thermally grown oxide mask.But, the sides of my wafer start etching out.I have tried PECVD Nitride as mask but that does not help.Is there any resist i can apply to the edges of my wafer during the last 1-1.5hrs of my etching Manjula _______________________________________________ MEMS-talk@memsnet.org mailing list: to unsubscribe or change your list options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk Hosted by the MEMS Exchange, providers of MEMS processing services. Visit us at http://www.memsnet.org/ __________________________________ Do you Yahoo!? Win a $20,000 Career Makeover at Yahoo! HotJobs http://hotjobs.sweepstakes.yahoo.com/careermakeover