Hi Lina,

I am not familiar with your coating system, but manual coaters
typically have a vacuum interlock switch in the line, usually located
close to the chuck.  The purpose of the valve is to prevent spinning
when there is a vacuum leak between the chuck and the wafer (or cover
slip, in this case).  It does this by closing a normally open
electrical switch when the system is under vacuum.  I have had many
similar experiences where some resist gets sucked into the vacuum hole
and solidifies, locking the vacuum interlock in the electrically
closed position, so the system thinks the vacuum is properly applied.
The way to fix this is to remove the interlock switch and clean it so
that it operates properly again.  In the worst cases, it would have to
be replaced or rebuilt.  If you want to rebuild it, make sure you
replace the o-rings with a type that are compatible with the solvent
system of your resist.

Brad
_________________________________

Brad Cantos
brad.cantos@holage.com
http://holage.com




On Sep 2, 2009, at 2:06 PM, lina wang wrote:

> Hey, all,
>
> We have a spin coating system (P-6708D) and I am trying to use it
> for SU-8
> coating. The chuck diameter is 1 inch and the substrate is normal
> coverslip.
>
>
> It worked fine before, but recently, we got some problem with it.
> Even at
> low speed (500 rpm), the coverslip will be thrown away. It seems
> that the
> coverslip will not be held by the vacuum.
>
> I suspect the problem is with the vacuum. First, I checked the
> vacuum pump,
> which works fine. Then I checked the connecting tube, and there is no
> leaking. When I pressed the "start" botton, the system did not give
> error
> message. So I suppose the system is fine. Do you get similar
> experience? Any
> other places I can check and repair to make the system work? I
> appreciate
> your time very much.
>
> Thanks,
>
> Lina Wang
> Driftmier Engineering Center
> University of Georgia