When you apply the SU-8 have the wafer rotating about 20 or rpm to get a
puddle that is centered every time.  You may have to change the slow spin rpm
for 2" wafers.  Also, start the spin cycle at a slow acceleration, say 200 rpm
per second.

Clif

Clifford J. Hamel
Suss Microtec Applications Engineer
(802) 244-5181, ext 297

>>> landry@anvil.nrl.navy.mil 03/15/02 08:24AM >>>
        I have a problem spinning SU-8 2050 photoresist (Microchem corp). When
I place the required amount on my 2" silicon wafer and spin, it does not
spread uniformly. Instead it all goes to one side (if it is not exactly
centered) or it spreads out in a starfish pattern, leaving large portions
of the wafer uncovered.
        I have tried manually spreading the SU-8 across the wafer, with my
pipette, but this introduces bubbles. It was also suggested to tilt the
wafer to get the SU-8 to spread, or to sit it on a table. Neither of these
suggestions worked, since the SU-8 2050 is so viscous and it takes so long
to spread with gravity, a skin forms on the SU-8 before it spreads.

Does anyone have suggestions?

Glen Landry
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