I think that this pulling back usually occurs during the baking.
I experienced such a phenomenon and it is usually because the hot plate I am
baking on is not perfectly horizontal which leads to pulling back from
edges.

To make sure if yours is because of that or not , you will find that it is
not pulled back from all the edges which indicates some inclination which
leads to the transportation of the su8 while its temperature is above the
glass transition state.

On Mon, Jun 13, 2011 at 4:53 PM, Shane GUO  wrote:

> Hi,
>
> I agree with Eric. We also found that the relaxation time was very
> important to us. We use SU-8 (50) and (25) for a 100um and 50um thick seed
> layer. However, we did find that the SU-8 coating was pulled back from wafer
> edges after a long relaxation. Did you find the same thing Eric? How to
> avoid that?