Lei,

it is possible to put a uniform coating on a rectangular substrate, or
at least to improve performance. You turn off the exhaust to your
spinner, and saturate the spinner environment with the solvent used in
the resist (sometimes by putting clothes soaked in it in there), and
close the lid. Then spin your resist. After the spin/spread cycle is
done, turn the exhaust on to initiate drying. this should help.

If your spinner doesn't have all these features automatically, you
should be able to rig something manual up. I did this years ago on small
rectangular substrates and got good improvement.

Good luck.

Rob MacDonald
Shearwater Scientific
www.shearwaterscientific.com


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