Good afternoon Jason,

Thank you for your response.  The suspended membrane is Si3N4.  I will search
for the properties of ProLIFT and see if it can work for a gap of 4 microns.
What photoresist developer do you use? Also, I will get more info about what you
call a  critical point dryer, it is the first time I hear about that (well, I am
new in microfabrication, maybe that explains why...).

Thank you very much :-)

Suzanne Paradis, eng. M.Sc.


-----Original Message-----
From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org] On
Behalf Of Jason Milne
Sent: July 6, 2009 11:02 PM
To: 'General MEMS discussion'
Subject: Re: [mems-talk] Removal of polyimide sacrificial layer

Hi Suzanne,

What is your suspended membrane made from? We used to use an oxygen ash of
polyimide to release a silicon nitride membrane, but found that the oxygen
plasma would change the curvature of the membrane. Now we use a wet release,
with a polyimide that can be wet etched even after exposure fairly high
temperatures, and we use an oxygen ash to controllably flatten our
membranes. So, the warping of your membrane may be unavoidable with an O2
ash, but you can use it to your advantage. The polyimide we use is ProLIFT,
which can supposedly stand up to 400C and still be wet-etched in photoresist
developer. Of course, if you use a wet release, then you'll need to use a
critical point dryer or your membranes will collapse.

Regards

Jason Milne
PhD Candidate
Microelectronics Research Group
School of Electrical, Electronic and Computer Engineering
The University of Western Australia