My experience is that SU-8 is very hard to remove with plasma after being
cured.

Maybe Piranha is a solution, but you should be very careful.

My suggestion is to clean the mask very time when it is stained. Simply
washing with acetone, alcohol and DI water will keep the mask in good
condition, and that is much more easy and safe.

Another thing to be aware, unexposed SU-8 is very sticky after lithography
due to heat absorption, if the soft-bake is not well conducted. I guess this
is the cause of SU-8 stain on your mask.

Try to bake the sample again on around 50 degree if you left the sample on
hotplate for a while, before lithography. This works for me to avoid very
thick SU-8 layer sticking to mask after lithography.

On Fri, Mar 26, 2010 at 3:04 PM, Andrew Irvine  wrote:

> Just to re-visit a wise warning from a recent poster, Piranha etch (at 110C
> or not) is seriously hazardous, and we need to be flagging up safety advice
> when suggesting stuff.
>
> I don't see a problem with using an oxygen asher, and if there is no
> problem (anyone?), do that instead, Mikas!
>
> Andy

--
Best Regards,

Ruilin Zheng

Institute for Microsystem Technology,
Vestfold University College,
3184 Borre, Norway