Provided you haven't baked it too hot during processing, acetone should
remove negative resist without affecting your metals. If you have baked
it on, then AZ has a product called Kwik Strip which removes baked on
negative resist quite well, although you might have to heat it up a bit
or else it can take hours.

I know from experience that the negative resist AZ2035 doesn't remove in
acetone if you take it above ~120C, which could easily be the case if
you did a thermal evap of nickel when the resist was on the wafer.
Exposure to CF4 plasma also seems to bake it on, even when the
temperature at the wafer surface is lower than 120C. I now use hot kwik
strip (~80C) for about 5 mins in either case, and I get much better
results than I used to get using an oxygen ash to remove the baked on
resist.

Jason Milne
Microelectronics Research Group
The University of Western Australia


-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Javier Crespo
Sent: Tuesday, 18 November 2008 12:43 AM
To: [email protected]
Subject: [mems-talk] selective negative resist stripper

Dear All,

Could anyone tell me how could I remove negative photoresist from a
silicon wafer without affecting metal layer (Ni or AlSi)?

I know that the piranha etching etches the resist in a higher rate than
the metal, but I don't know in which percentage.