Chad:
On the other hand, and depending on the exposure system, one
can get reflections off the chuck, through the glass.  I had
this problem with an old stepper, where the vacuum chuck has
a corrugated pattern, causing all kinds of reflections.  You
can try something like black tape on the chuck or on the
bottom of the glass and see if this makes the exposure
better. Not a solution, but will indicate where the problem
is coming from.
-Bill

---- Original message ----
>Date: Tue, 2 May 2006 09:03:19 -0700
>From: "Brubaker Chad" 
>Subject: RE: [mems-talk] photolithography on glass problem
>To: "General MEMS discussion" 
>Cc: Brubaker Chad 
>
>Alex,
>
>Another thing to remember is that your dose will change when
exposing a
>glass substrate vs. A silicon substrate with SiO2 on it -
the silicon
>surface is still reflective, while the glass surface is
minimally so.
>You will probably need to increase the dose to make up for
this lack of
>reflection.
>
>Best Regards,
>Chad Brubaker
>