Hi Melissa,
We also bake before spinning 200C for 30 min.
Are you using a hotplate or an oven to soft-bake? If you are using an
oven, the resist will sometimes solidify on top leaving the bottom still
swimming in solvent. Using a hotplate bakes from the bottom first.
Also, make sure that you are filtering out wavelengths of light below
360 on your exposure. That can also cause your problem.
I've never had any luck with adhesion layers for SU-8 on Si, but I've
always gotten the SU-8 itself to adhere.
Greg Reimann
Boston University
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of
Karin Buchholz
Sent: Wednesday, February 11, 2004 12:27 PM
To: General MEMS discussion
Subject: Re: [mems-talk] SU-8 adhesion problem
Hello Melissa,
Usually the adhesion of any resist is much better when the
samples are dry. So try putting them in an oven (we use 90degree)
for 15 min before applying the resist, this will remove the
condensed water from the surface.
HMDS usually also helps. (we use 10s 3000rpm, but this should
not make much difference)
Good luck,
Karin
[email protected] wrote:
> Hi,
> Am trying to spin about 3-5 um of SU-8 onto a silicon wafer but was
getting
> some problems of adhesion and the SU-8 came off during the development
step. I
> read on this discussion group that HMDS was recommended to help with
the
> adhesion of thicker layers of SU-8. I tried spinning HMDS ar 5000
rpm/30 sec
> before spin-coating the SU-8. However, during the pre-bake step (95
degrees
> for 2 min), the layer of SU-8 shrunk from the edges of the wafer. What
is the
> reason for this and how can I prevent it if I want to use HMDS to aid
SU-8
> adhesion? Thanking you in advance.
>
> Regards,
> Melissa
>
--
Dipl.-Ing. Karin Buchholz
Walter Schottky Institut
Technische Universitaet Muenchen
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