You will have to remove the edge bead manually.
Increasing spin time will help with thickness uniformity
I believer the resist should be pre-baked between consecutive spinning
cycles to "add on" to thickness. I'm not so sure about that - check
manufacturer's data sheet.

Elina Kasman

Process Development Engineer, R&D
Engis Corporation
Phone: 1(847) 484-7225
E-mail: ekasman@engis.com

-----Original Message-----
From: vaibhav mathur [mailto:kingvaibhav@hotmail.com]
Sent: Tuesday, April 22, 2008 5:51 PM
To: mems-talk@memsnet.org
Subject: [mems-talk] SU-8 2

hi all,

I use microchem SU-8 2. At 2000 rpm I achieve 2micron thickness. Now I
want  to increase the height to 5-6 microns. how do i do this??

1) when I spin coat at 1000 rpm I get about 5 microns, the height is
inconsistent though, and i get very bad edge bead. can someone suggest
how to do this properly

2) also, if I do double spin coating, I should get 4 microns, right? but
I get only about 2.4 microns, an increase of just 20 percent, I dont
understand.
Does someone have a recipe for double spin coating of SU-8?