If you are doing contact printing, we sometimes put an array of small
boxes (or ID #'s) on the main mask and then when shooting each
substrate, put a small bit of tape to mask off a different one of the
marks. I.e., the wafer with the first ID box missing is wafer number
1, the wafer with the second box missing is wafer 2, etc. You can
also develop the whole array of ID marks and then recover one of the
boxes with a dab of resist.
On Sep 4, 2007, at 1:25 AM, 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.
>