Owen,

I'm unsure whether it would make a difference of 50%, but one place to start
would be your spinning time. You say you "hold for a few minutes," which is
beyond the recommended spinning time of 30 seconds.

See the data sheet at:
http://www.microchem.com/products/pdf/SU-82000DataSheet2100and2150Ver5.pdf

You might also want to lose the acetone in a covered petri dish step.
Evening out of the surface by dissolving a different solvent into your
resist could certainly affect it during the soft bake.


Kevin Paul Nichols
MESA+ Institute for Nanotechnology
Mesoscale Chemical Systems
Meander 151
University of Twente
Postbus 217
7500 AE Enschede
The Netherlands

Office: +31 (0)53 489 26 31
Mobile: +31 (0)6 49 312 471
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Web   : http://mcs.tnw.utwente.nl/


On 3/24/08 6:16 AM, "Owen The"  wrote:

> Hi all, I've been having some trouble with my SU8 Processing.
> Currently I'm using SU8 2100. I'm trying to get a postbaked thickness
> of 260um, but I've been consistently getting half the quoted thickness
> (130um in this case) for any given speed.
>
> Here's my processing steps:
>
> 1) Wafer prep
> 2) Dispense 4ml of SU8 on a slowly spinning wafer (to center the blob)
> 3) Ramp to the set speed (in this case 1000 RPM), hold for a few minutes and
> then stop
> 4) Rest in a covered petri dish on top of a small filter with a little acetone
> (to even out the surface)
> 5) Softbake (ramping to set temps)
> 6) Expose and postbake (ramps to temps again)
> 7) Develop in acetone, rinse with isopropanol and water
>
> Not sure what I'm missing, but I've done this process with other
> grades of SU8 and have always seen 50% of the quoted film thickness.