Li Wang,
I'm not sure if you will have much luck with observing the patterns of the lower
level structure at all, especially since your upper level is so much thicker.
Due to the nature of SU-8, it will tend to self planarize itself during the soft
bake. Since the 50 um layer has so much additional material, the top surface of
your coating should be pretty flat. Since the optical properties of crosslinked
SU-8 are very similar to that of uncrosslinked SU-8, it means that the films
will be, optically, nearlt indistinguishable.
In other multi-layer patterning processes I've seen, a set of alignment keys was
placed directly onto the substrate initially for alignment purposes. Because of
the transparency of the material, the first layer pattern should not interfere
at all with alignment of the second layer.
Best Regards,
Chad Brubaker
EV Group invent * innovate * implement
Technology - Tel: (602) 437-9492, Fax: (602)437-9435 e-mail:
[email protected], www.EVGroup.com
This message and any attachments contain confidential or privileged information,
which is intended for the named addressee(s) only. If you have received it in
error, please notify the sender immediately and then delete this e-mail. Please
note that unauthorized review, copying, disclosing, distributing or otherwise
making use of the information is strictly prohibited.
-----Original Message-----
From: [email protected] [mailto:mems-talk-
[email protected]] On Behalf Of Li Wang
Sent: Tuesday, November 25, 2003 6:29 PM
To: [email protected]
Subject: [mems-talk] about 2 level sof lithography
Hi all,
I'm working on 2-level PDMS structure fabrication so that I should spin
SU-8 twice. But I met a problem when I align the two layers. Since the two
layers are both SU-8 and SU-8 seemed transparent, it really hard to observe
the alignment mark under the microscope during the alignment process. My
first layer is about 7um, second layer is 50um. Did anybody met this
problem? Any ideas about this?
Another issue is that according to some papers from Whitesides group, they
said the first SU-8 should not be developed. I couldn't find the reason why
the first layer should not be developed. Is there anybody can give me hints
for this issue? I tried developed and undeveloped the first layer.
Developed can be a little bit better, but still not enough to clearly
observe under microscope.
Thank for your help.
Li Wang
412-2682514
Carnegie Mellon University
_______________________________________________
[email protected] mailing list: to unsubscribe or change your list
options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk
Hosted by the MEMS Exchange, providers of MEMS processing services.
Visit us at http://www.memsnet.org/
