Dear Le Hong,

        It is very true that with a non circular wafer, you cant get a
uniform thickness especially with large thicknesses. for the bubbles, try to
do the spinning immediately after you put the SU8 on the wafer.with very
large thicknesses, I recommend you bake at smaller temperature with longer
times. This will decreases the issue of bubbles appearing while soft baking
and will reduce the internal stress on the film. If you bake only at 65,
"Longer Times" would mean triple to 4 times the soft baking at 95.

      For removal, once you cross-link the su-8 with exposure, it is very
hard to remove it with any thing. For me honestly, nothing removes
Cross-linked SU8 but piranha clean. This is because cross linked SU-8 is
meant to be remaining as a structure.

Thanks
Regards,

Khaled Ramadan
King Abdullah Of Science and Technology
M.Sc. Electrical Engineering
Saudi Arabia

On Wed, Jun 8, 2011 at 11:24 AM, Le Hong Hanh  wrote:

> Hi all,
>
> It's first time I use Su-8 2010 for a micro-fabrication. Generally
> speaking, Su-8 PR has been made me some trouble such as air bubbles appeared
> when soft baking, non-uniformity with a non-circular sample. Now, the most
> difficulty is Su-8 removal. I have spent over 1 hour to remove Su-8 layer
> after a Si etching. The PR layer is about 10 um. I put it in acetone
> solution with a ultrasound cleaner for over 1 hr. But I see that there is
> little Su-8 removed (it made the solution cloudy). It seems nothing has been
> changed on the wafer surface.
>
> Please show me your experience on removing this PR!
>
> Thanks,
> Aboto