For such thick SU-8 I will not recommend spinning. It will give you big
problems with uniformity and you will need to spin and bake like 5 times
in sequence.

Casting SU-8 in that thickness is much better.
It works like this:
1. place your wafer on the levelled hot plate.
2. Add SU-8 to the center of the wafer by a syringe or a pipette.
3. Wait until the SU-8 has spread over the entire wafer.
4. Ramp up the temperature slowly (over 2-3 hours) to 100-110 deg. C and
bake over night. Feel free to optimise the bake parameters, but be
advised it will take a long time!
5. Lithography .... as normal.

You need to calculate the volume of SU-8 you need to dispense to acheive
the desired thickness. Assuming the SU-8 is a cylinder works well (1 mm
tall in your case). You need to take the solid SU-8 content into account
(it is written on the bottle). i.e. if it is a 50% solid content SU-8
you need to dispense double the volume corresponding to the thickness
you want.
This method works best with the thinner formulations of SU-8 since it is
difficult to make the thick formulations spread over the entire wafer.
You will be surprised how much liquid SU-8 can be held on top of the
wafer without it spilling. However, for very thick layers and thin
formulations you must be careful because once the SU-8 goes over the
edge there is no stopping it. Have acetone and wipes handy!

I have succesfully made high uniformity castings from 200 um to 2 mm
using this method. The thickness can be controlled very accurately
(1-2%) when dispensing by volume, and even better if you dispense by
weight (the wafer on a high accuracy weight while dispensing).

Regards

Jacques Jonsmann

-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of Abhishek Jain
Sent: Sunday, April 13, 2008 9:28 AM
To: General MEMS discussion
Subject: [mems-talk] su8 1000um thick

Dear forum members

I want to make 1mm thick structures on SU8 for doing soft lithography
with PDMS later on. It is only one mask and just straight channels.

I have SU8 2075 with me and I am trying to find a recipe for doing this.
If anyone has experience in dealing with this, I will truly appreciate =
if you may give some insight on the method...