Hi Lando,

I use similar process (beside Step 3) without problems. So there are only
two possibilities:

1.) Your evaporation is too hot, mostly if the sample is too close to the
crucible (if it is thermal or e-beam evaporation).
However, PMMA is much more robust to heat then most common photoresists. So
check with other users of your equipment if they have the same probs.

2.) Your ozone stripper weakens the PMMA too much. In most cases, a short
oxygen plasma should help to remove any resist residues.

What are your PMMA baking temps?

Best Daniel



-----Original Message-----
From: mems-talk-bounces+d.grimm=ifw-dresden.de@memsnet.org
[mailto:mems-talk-bounces+d.grimm=ifw-dresden.de@memsnet.org] On Behalf Of
landobasa
Sent: Mittwoch, 2. Juni 2010 05:09
To: mems-talk@memsnet.org
Subject: [mems-talk] PMMA cracking during e beam evaporation

Dear Researcher,

I am still a beginner in fabrication, and I have these following problems in
the lift-off process. In order to provide the context, let me briefly write
the process steps:

1) PMMA film (200nm thickness) is patterned using Electron  Beam Lithography
(developed for 60s and IPA for 30s).
2) Patterned PMMA film was subjected to UV Ozone Stripper (SAMCO UV-1) for
60s.
3) The sample was deposited by Ti with 20nm thickness (with the rate of
0.06nm/s)
4) The sample was soaked in Acetone.

Problems:
1) There are cracks everywhere in PMMA film after E-Beam Evaporation.
2) The PMMA cannot be removed by acetone.

Any help would be very much appreciated.

Best Regards,

Lando