Dear Lei,

      I would try two approaches:
1. expose the outer edgebead with a high mag objective using white
light so that it develops away
2. try using an acetone reflow process to even out the edgebead.

Good luck!

Felix


On Feb 10, 2010, at 8:01 PM, leiwangsdu wrote:

> Hello, everyone. I use the positive photoresist to do some
> lithography.
> I have a big problem. My samples are rectangular which have
> dimensions 10mm*15mm
> After the resist spinning, I found that the resist film around the
> edge of the sapmle is thicker
> than the resist in the center. This produces a gap when the contact
> exposure is applied.
> And the resist profile is not good enough after the development.
> I  shall be highly obliged if anyone can help me out in this and
> provide some advices.
> Thanks in advance
>
> Yours sincerely,
>
> Lei Wang

Felix Lu
felix_lu@yahoo.com