Hi Basar,

There are 3 things I suggest you to try based on your email

a) If you have a convection oven, prebake PMMA for 10 mins at 160-190 C in
the oven.
b) Postbake of PMMA at 95 C for 5 mins in convection or 1 min on hot plate
is routinely used. Try this.
c) If the metal of lower thickness is not peeling off, the problem is
straight forward, the metal is melting your resist. In this case, I suggest
you to deposit in small steps. Close the sample shutter once every 5 nm to
10 nm and allow the sample to cool down for about 3 minutes or so. Nickel
requires considerably higher power to melt than gold, and if thickness
required is fairly high, and if deposition rate is in Angstrom/Second, most
likely the sample temperature is higher than 250 C for a long period of
time, causing the resist to melt. Also this will cause degasing of your
resist and create bubbles. You should avoid long deposition times to avoid
peel off.


Ananth

---------- Forwarded message ----------
From: basar bolukbas 
To: 
Date: Fri, 23 Jan 2009 23:08:48 +0200
Subject: [mems-talk] PMMA-950K-A6 resist peeling problem after Ni-Au
deposition
Hi Dear Ananth

a) My prebake receipe is : 180C-60s. in hot plate.
b) For lower thickness, yes you are right, i observed less peeling problem.
c) I dont think that if there is a organic residue layer on my sample, but i
will try your receipe.
d) My substrate is SiC-HEMT.

Thank you very much for helping.

Best Regards.
--
Ananth Krishnan
Texas, USA