Hi,

the swelling may be appear due to heating of the SU-8 during exposure.
Depending on the power of your UV source, it is better to make multiple
exposures with few seconds and a delay in between (for 30µm: 4x3.5sec @
10mW/cm2 and 30sec pause)

The adhesion problem depends on your substrate It has to be very clean and
use a dehydration bake before spin on (30min @ 200°C). Due to my experience,
on SiN/SiO the adhesion is poorer than on pure silicon.

Try to use temperature ramps for the soft- and hard-bake to reduce the
stress in the SU-8 layer.

Good luck
Christoph

_________________________________________

Dipl.-Ing. Christoph Friese

IMTEK - Micro-optics
Georges-Koehler-Allee 102
D-79110 Freiburg
Germany

Fon: +49 (0) 761 203-7575
Fax: +49 (0) 761 203-7562
Mail [email protected]
_________________________________________


> -----Ursprüngliche Nachricht-----
> Von: laetitia philippe [mailto:[email protected]]
> Gesendet: Donnerstag, 2. Dezember 2004 15:40
> An: [email protected]
> Betreff: [mems-talk] SU8-developpement problems
>
>  Hello All,
> I am using the SU-8 2035 for making film thicknesses of 50 microns.
>
> I am proceeding with the soft and hard bake in a normal way.
> After my exposure I can see clearly that around the structure
> I have considerable swelling of my polymer, around 100% of my
> original thickness. SOmetimes the polymer sticks well,
> sometimes it delaminates from its region
>
> Also, the structure I expose is somewhat always minored in
> dimensions in comparison of my original mask.
>
> Has someone ever encountered this problem?
>
> Is it due to a wrong exposure time (I am using a UV source ,
> 365 nm), 7 to 9 seconds?
> Is it due to a bad curing? maybe should be longer to reduce
>
>
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