It's pretty difficult to get a layer that thick, but first off it will
depend on the SU8 you are using.  In order to achieve thicknesses in
that range you will be best served using SU8 2100 or 2150.  These are
very viscous and dispensing them can be problematic.  In addition you
will have to do a multilayer process.  For example using 2150 at a spin
speed of 1000 rpm will give you around 650 um.  To achieve a 2 mm layer
it will require 3+ layers. After each layer you will have to do a soft
bake, but beware of over baking the under layers during the 2nd and 3rd
bakes.  If you put too much heat into them it can cause a sort of
thermal crosslink which will inhibit you from being able to fully
develop away the material.  I  would do shorter bake times on the under
layers, just enough to drive a good majority of the solvent out, leaving
the film firm but still a bit tacky to the touch!

Good Luck!

Best Regards,
Mike Sexton

EV Group
invent * innovate * implement
Process Technology Engineer - Direct: +1 (480) 305 2450, Main: +1 (480)
305 2400 Fax: +1 (480) 305 2401
Cell: +1 (602) 625 1275
E-Mail: M.Sexton@EVGroup.com, Web: www.EVGroup.com

-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of A. AhmadShukri
Sent: Wednesday, November 26, 2008 12:31 PM
To: General MEMS discussion
Subject: [mems-talk] very thick layer of SU-8

Hi all--

I am wondering if anyone knows how I can deposit a 2mm (yes, 2,00um)
layer of SU-8 and pattern it.

Thanks,

Aimi Ahmad-Shukri
Dept of Mechanical Engineering
University of Washington