Dear Leo,
 I agree with Kevin, you´ll likely get into problems
with so thik SU-8 ´layer´ specially about solvent
evaporation ( bubbles and wall distortions) and very,
very long time of pre-bake ( even with multilayer). If
you have to use SU-8, you can, but if not, there are a
lot of resists more suitable or even better you should
go to micro machining directly a sheet of appropriate
material.

Regards


--- Xiaoguang Liu  skrev:

> Dear MEMS community
>
> I'm looking into the possibility of using SU-8 to
> form rectangular cavity of
> about 4mmx4mm and 700-900um deep. From SU-8
> datasheet, it seems that >200um
> SU-8  is possible with a single spin coat. So I
> guess maybe multiple coating
> of SU-8 could possibly approach the thickness I
> want.
>
> I do not have any experience with SU-8 and I'm
> seeking advice from more
> expeienced users. Thanks a lot.