I am looking for a protective coating or tape to stand up to KOH for an
extended period.  At the end of the etch my wafers are thin.  I am
mostly concerned with the outer rim of the wafer, where even small
scratches become great cleavage planes.

I realize that there are a couple commercially available coatings, such
as Protec or BPR100.  Does anyone know which ones are better for long
processing?  Also, I am etching my wafer on both sides, so I can't spin
on a protective coating.  I wonder if I can simply paint the edge of
the wafer with these coatings and then bake them.  Will they still be
resistant to KOH?

Are there any other products or ideas that I should consider?

Thank you,
Arthur Beyder
SUNY at Buffalo