We use a 0.1 M KOH solution to remove Al that was an overcoat
on PMMA.  We have not seen any problems with this.

>
>Dear colleagues,
>
>We were trying to do some ebeam lithography in PMMA950C5 spun
on an Al
>coated wafer. When we were etching Al after the PMMA
development, the PMMA
>changed colors and was apparently attacked. As far as I know,
Al deposition
>on PMMA with non-conductive substrate to improve the EBL
resolution is a
>very common process, then how come the Al etchant attacks the
PMMA? The
>etchant we used is "Aluminum Etchant Type A" from Transene.
>
>Any suggestion to avoid this attack is appreciated.