The selectivity of an O2 plasma on an oxide surface should be infinite. Ed Sebesta -----Original Message----- From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org] On Behalf Of Evelyn B Sent: Sunday, March 22, 2009 10:19 AM To: General MEMS discussion; Evelyn Benabe Subject: [mems-talk] Selectivity I will be doing both descum and ashing of both positive and negative resists as part of my process flow and would like to know what is a good selectivity number for a dry process as there will be oxides present on the wafer. I will be doing both the descum and ashing processes using O2 gas.