Hi Nirmal,

That's a very slow spin speed, so it's going to be tough to get a flat
surface. My suggestion is to spin at 800 rpm and postpone the
pre-bake. Instead, place the wafer on a flat level surface for a day
or two (cover it so that it stays clean) to allow the unbaked resist
to self level. I don't know if it will meet your requirements for
flatness, but it should be better than spinning only.

Best,
Joe Grogan



Quoting Nirmal punjabi :

> Hi,
>
> I need a thickness of around 400um of SU-8, i am spin coating SU-8 2100 at
> 800rpm for 60 sec.
>
> But the final structure formed has uneven surface.
>
> Can anyone help me on this matter?
>
> Thank you.
>
> Nirmal.

--
Joseph M. Grogan
Doctoral Candidate
Department of Mechanical Engineering and Applied Mechanics
University of Pennsylvania
220 South 33rd street
Room 229, Towne Building
Philadelphia, PA 19104
Lab Phone: 215-898-1380