If you have a free spot somewhere on the device side your wafer, you
could manually apply a dab of photoresist after developing your actual
pattern, maybe with a syringe or something, so that that mark carries
through when you evaporate and then lift off. Depending on how steady
your hand is, you might be able to write letters or numbers with the
syringe.
-Joe Grogan

Svyatoslav Alimov wrote:
> 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.