Joao, you might try dispensing the resist while the wafer is slowly rotating
(about 100 rpm,) very close to the wafer surface, in an effort to shear the
descending column of resist to impose it in the openings. dispense either
from the inside outwardly or outside inwardly, or alternatively right the
way across the wafer from edge to edge. Gary
Gary Hillman
S-Cubed
PO Box 365
9 Mars Ct.
Montville, NJ 07045
phone 973-263-0640 ex 35
fax 973-263-8888
Check out our web site and Twitter at www.s-cubed.com
-----Original Message-----
From: mems-talk-bounces+garyh=s-cubed.com@memsnet.org
[mailto:mems-talk-bounces+garyh=s-cubed.com@memsnet.org]On Behalf Of
João Tiago dos Santos Fernandes
Sent: Thursday, December 20, 2012 1:58 PM
To: mems-talk@memsnet.org
Subject: [mems-talk] Spin-coating of thick photoresist over existing
features
Hi everyone,
I'm currently using AZ 40XT thick photoresist to make a 20-30 µm thin film
over a Si sample with ~30 µm high SU-8 features.
The problem I am facing is the following: when I pour the AZ on top of the
sample, tiny air-bubbles are created in areas where SU-8 features are small
(small wells, gaps, etc) - I'm guessing that this happens because the AZ is
very viscous and isn't able to fill those spaces and traps air. When I spin
coat, those tiny air bubbles are spread across the sample, compromising the
process.
Is there any way to get the air bubbles out of the way without compromising
the final film thickness? I tried low rpm for a couple of minutes, with no
success.
Thank you so much,
-----------------------------
João Tiago dos Santos Fernandes
INESC Microsistemas e Nanotecnologias (INESC MN)
Rua Alves Redol, 9
1000-029 Lisboa
Portugal
Tel: +351 213100237
Email: jfernandes@inesc-mn.pt
URL: www.inesc-mn.pt
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