Zak,

    Great question.  You did not say positive or negative resist.  I
guessed positive.  My first input hard contact implies sometrapped air
and the UV exposure breaks down the oxygen in the trapped air to Ozone
and or oxygen plasma.  If Ozone it eats the resist and gives thinner
resist so faster develop.  If Oxygen plasma it eats the resist and the
olasma has a strong UV component so it exposes harder and you get faster
develop.  Colleague Ken Sautter says probably easier  Vacuum exposure
pulls solvent out of resist giving denser resist longer develop.  At
least 3 possibilities.

Bill Moffat

-----Original Message-----
From: mems-talk-bounces+bmoffat=yieldengineering.com@memsnet.org
[mailto:mems-talk-bounces+bmoffat=yieldengineering.com@memsnet.org] On
Behalf Of Zak Clark
Sent: Thursday, August 19, 2010 12:20 PM
To: mems-talk@memsnet.org
Subject: [mems-talk] Hard vs. Vacuum Contact Lithography

In our wafer processing we interchangeably use hard and vacuum contact
lithography depending on the wafer geometry (and alignment tolerance).
We have found that simply reducing the develop time, while maintaining
all other parameters, results in a comparable process.

So, why would a pattern exposed in hard contact develop faster than the
same pattern in vacuum contact?

Thanks,

Zak Clark
OptiComp Corp.