The asher will eventually do the job, but you may have to let it run for a very
long time, and there's a good chance you will have to contend with problems
related to heating of your sample.  If you have access to it, oxygen RIE can be
much faster and more effective than a barrel asher.  I've used a bench-top ICP-
RIE to strip cross-linked PMMA with good success.  If you want to be extra
thorough, you can use piranha much more safely after the RIE has taken out most
of the organic material - piranha can be very violent if you give it a lot of
organic matter to oxidize at once.

Even if you don't have a specific oxygen RIE, many DRIE tools have an oxygen
cycle for chamber descumming which can also be used for organic stripping if
your facility's SOP allows.

Solvent-based strippers (acetone, NMP, etc.) won't help you on cross-linked
resists, don't bother with those.

-Mike

On Jun 22, 2010, at 19:18, ameya g wrote:

> Hi
>
> I have a combination of PMMA and photoresist AZ3312 on an oxide substrate
> that was hard baked
> to 170 C for 2 minutes. The film appears shattered like a piece of glass and
> the thickness is
> anywhere from 0.01-0.1 um. The resist is really stubborn and has not yielded
> to any of the
> following methods so far -
>
> - Microstrip 2001 at 70 C for 1 hour
> - Asher at 200W for 4 hours
> - Piranha clean at 100 C for 3 hours
> - AZ 300MIF developer for 1 hour
> - Acetone at ambient for 1 day
> - Acetone at 50 C in Ultrasonic bath for 3 hours
> - Nano-remover PG at 80 C for 3 hours
> - Nano-remover PG at ambient for 4 days
> - Nano-remover PG at 50 C in Ultrasonic bath for 1 hour
>
> Has anyone ever had to deal with the removal of extremely hard baked
> photoresist?
> Any suggestions will be greatly appreciated!
>
> Thanks,
> -Ameya