[labnetwork] Photomask sticks to SU8

[Jasper Nijdam]

Heho Long,

Couple things:

* Optimize your baking. Get your SU-8 less sticky. SU-8 baking is very lab
dependent. Depends on your local airflow - things like whether your hot
plates are in air flow or not. Ramping matters too, all hot plates are not
the same. Do not fare blind on the spec sheets from Microchem. Maybe lower
and slower might help you. Play around a bit with your local set-up.
* Make sure your baking happens very horizontally. Until crosslinked, SU-8
is a very slow liquid. It will flow to the lowest side of a wafer. The
thickness difference will cause one side not to be done.
* Reduce the force in your alinger between the mask and substrate. The
harder you squeeze, the larger the chance it will stick.
* SU-8 is sticky nasty stuff. There will always be some sticking,
especially with students who are not top experts in litho. As long as your
features aren't super small, it'll be fine. For small features, they will
either learn, or give up. This is where you find out who the really good
students are. Be nice to the good ones. They will do amazing things.

You can clean with SU-8 developer or IPA.

One final SU-8 tip: Keep SU-8 very far away from water - including water in
your solvents. SU-8 will create a milky liquid with water. Avoid that. It
will mess things up. Get good clean e-grade IPA for rinsing.

-- 
Jasper Nijdam
Technical Manager GNuLab, Georgetown University
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