At 01:41 PM 10/11/2004 -0400, you wrote:
>Hi,
>Im trying to pattern su-8 on glass (square, rectangular slides). Edge bead
seems to be inevitable. Suggestions on minimizing them would be really
appreciated. thanks, krishna
>
>```````````````````````````````````````````````````````````````````````````
``````````````````````````````````````````````````````
>Krishna Vummidi
>

If you must spin coat, a chuck with a pocket shaped for your slides would
work.
The pocket depth needs to be the same as the thickness of the slide.

Another method is roll coating.  In this process, you place the slide
between two straight edges.  The straight edges are located at a set height
above the slide.
After a large drop of your material is placed at one end of the slide, a
rod is rolled along the straight edges to distribute the resist over the
slide.
Alternatively, a knife edge can be used in the place of the rolling rod.
For very high viscosity materials, a stop on the base will be needed to
prevent the slide from moving.  Another slide taped to the base would work.

        _________________________________
       |        rod or knife edge        |
       |_________________________________|    ________________
         /\                           /\             ^  coating thickness
         ||      _______________      ||    _________v________
         ||     |    slide      |     ||
         ||     |_______________|     ||
--------------------------------------------------
|                  Base                          |
--------------------------------------------------


--
Mark Fuller
Microelectronics Fabrication Facility
Washington State University
Dana Hall 102
Pullman, WA  99164-2711
(509)335-1797