Vishwa,
I have not encountered this myself, but it is apparently some form of
crosslinked SU-8 material, perhaps combined (reacted) with the IPA rinse
solvent (assuming you rinsed with this, of course). If this is the case,
try developing with SU-8 developer (PGMEA), and rinsing with a
compatible solvent/mixture (such as PGME/PGMEA mixture).
Another possibility is that it is a patch of SU-8 that for some reason
became a little rougher during develop, and so the "coloration" is due
to diffusion of light. This could indicate an overexposure (perhaps
some exposure to UV below 350nm?). Also, SU-8 does have a thermal
crosslink temperature as well (I forget whether it is 110C or 150C at
the moment).
Best Regards,
Chad Brubaker
EV Group invent * innovate * implement
Technology - Tel: 480.727.9635, Fax: 480.727.9700 e-mail:
c.brubaker@EVGroup.com, www.EVGroup.com
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-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of Vishwanath
Somashekar
Sent: Monday, June 27, 2005 10:07 AM
Cc: General MEMS discussion
Subject: Re: [mems-talk] Reg: problems with SU-8 bonding to the silicon
wafer
On 6/23/05, Brubaker Chad wrote:
> The best suggestion I can make for the alignment is to do a simple
> masking step on the bare wafer, to put basic alignment keys (you could
> possibly even use the first level mask of the SU-8). Then, do a
shallow
> etch to define the patterns. You will then have alignment keys for the
> second layer.
>
HI,
I tried your suggestion which required that I spin the second layer
before developing the result. I have not yet tried to cast PDMS to
this microchannel and hence not sure if the layer will stick to the
wafer. However, I did notice that i see some patches on the
microchannel, which have the color of smoke. My first thought was that
I have not developed SU-8 enough. But I found that no matter how long
I develop, these pathches exist on the channel and the rest of the
wafer is absolutely free of SU-8. Have you encountered such problems
and if so what is the remedy.
Again, thanks a bunch for the help
Vishwa
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