Hello,

I am graduate student in Brooklyn College and I am trying to reinvent the whole
MEMS procedure as I do not have any professional help. My science adviser is
from another field.

I am having difficulties with the developing of SU-8 2025. Here is what I am
doing:

I am spin - coating 4 inch Si or Pyrex wafer to 50 - 60 um thin film
Pre - baking at 96 degrees for 15 min
Sometimes instead I am putting the wafer in the vacuum chamber of my UV
imprinter. The vacuum is taking away the solvent and clear most of the bubbles.
UV exposure with a hand made Imprinter: Xenon lamp 22kV at 10 microsec. pulses.
Three 30 seconds exposures with couple of seconds pause.
UV lamp creates heat so the wafer is let for 2 - 3 min to relax.
Post bake of 15 min at 95 degrees.

Developing by tenderly shaking the wafer in a vessel with Propylene glycol
monomethyl ether forever.

The result is that I clearly can see my pattern as exposed SU-8 is yelowish but
the unexposed parts are not removed and form thin film with the exposed part.
Less exposure leads to removing all of the polymer.
(This is happening even without any mask but the pattern is formed by metal
structure that divides 4 inch wafer into several smaller regions.)

Can anybody figure out what is my mistake?

Thank you
Dimitar Dimitrov
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