I would mark the backside of the substrate using a diamond scribe. Bob Henderson -----Original Message----- From: Svyatoslav AlimovTo: General MEMS discussion Sent: Tue, 4 Sep 2007 12:25 am Subject: [mems-talk] Numbering of substrates in a batch Dear MEMS community, I need to distinguish every substrate produced in the same batch of 2 step lift-off process, e.g. with the same mask. Could you suggest some simple way how to mark them without changing the mask for every substrate? Producing scratches, coloring with permanent marker or attaching of adhesive stickers are not acceptable. Thanks. Best regards, Svyatoslav Alimov