Lee,

"Over-crosslink" for SU-8 really cannot occur.  When the process is
complete, SU-8 is already completely crosslinked.

Additionally, part of the reason the data sheet says to PEB immediately
is that, once exposed, the material will crosslink over time at room
temperature anyway.

Finally, its probably best to do the PEB prior to the second layer, both
to make sure the exposed regions stay stable, and because the PEB will
effectively occur during the processing of the second layer anyway.

Best Regards,
Chad Brubaker


-----Original Message-----
From: Chen-Han Lee
Subject: RE: [mems-talk] multi-layer SU-8

Hi Ren,

thanks for the information
just one thing, between exposuring of the first layer and depositing of
the
second layer,
is it necessary to do a post-expose bake?
cos I think the first layer su-8 will be over-crosslinked if the
postexpose
bake is performed.
on the other hand, a post-exposure bake must be performed immediately
after
exposering, according the datasheets.