Hi,

I experienced sililar problems. I usually use DECONEX or RBS 50 to clean
glass (Borofloat) substrates. This is a
laboratory cleaner with high pH and I apply a 10% solution ( pH is at
least 12).
After the Deconex step the wafers are thoroughly rinsed in DI Water and
finally
Megasonic cleaned to remove particles, followed by a dehydration bake
(15 min at 120 deg C)
prior to spin-coating.
I observed that the adhesion of SU-8 is much better if the wafers are
immersed in the
Deconex solution for an extended period (1 day). Probably the surface of
the glass is
etched because of the high pH and long time and therefore some surface
roughness might be  induced, which
enhances adhesion. This roughness does not matter for our structures.

Anyway, an extended PEB is useful as well. We have to develop buried
microchannels and therefore
we have to develop the SU-8 for at least 2 hours. To avoid cracks and
delamination we apply
a two-step PEB: 10 min 90 deg C, followed by 12 hours at 60 deg C
(hotplate).

Best regards

Peter Svasek

--
Vienna University of Technology
Institute of Sensor und Aktuatorsystems
Gusshausstrasse 27-29/366
A-1040 Vienna
Austria

Tel. +43-1-58801-36643
Fax  +43-1-58801-36699




X Chen wrote:

>Another thing from my experience. The adhesion between SU-8 and glass
>substrate seems fairly much depending on the surface conditions
>(maybe roughness) of the substrate. There are a couple of times I ran
>borofloat wafers using exactly the same process (pirahna cleaning,
>dehydtration, spinning, soft bake, exposure and PEB) but SU-8 patterns
>show up nicely on some wafers without any peel off after development
>for a few mins, while nothing is left on other wafers with the same
>develop time. Because the wafers used are mixed from different vendors, I
>could not trace down the difference between their surface quality.
>However, besides surface conditions, I could not think of any other
>factors contributing to this huge difference in adhesion. So, try some
>other glass substrates if nothing else helps.
>
>Xianling Chen
>
>
>
>