All,

Thank you for the replies, I have some experience using UV to generate ozone
for surface cleaning (SPM tips and such) so I have a bias towards that
explanation. A bit more input is that we are in fact using positive tone
resists, and we see very similar behavior between different viscosities of
like resists (AZ4110, AZ4330, and AZ4620). Out of interest, I might have to
play around with the pre-exposure bake to see if the solvent content stands
out as a key player, since that would be easy to test.

Thank you again for your insights,

Zak

-----Original Message-----
From: wangningyuan [mailto:wangnyuan@hotmail.com]
Sent: Thursday, August 19, 2010 2:06 PM
To: mems-talk@memsnet.org
Subject: Re: [mems-talk] Hard vs. Vacuum Contact Lithography

Hi!

Good points! Just add something more. I think your colleague Ken Sautter
point out something interesting about the solvent. I assume the same will
happen to the moisture in the photoresist, which is important for the speed
of develop process. That is why somebody hold their sample for a long period
for the thick photoresist process. I think the name is rehydration.

Hopefully this helps!

Best regards,
Ningyuan Wang

> Date: Thu, 19 Aug 2010 13:37:07 -0700
> From: BMoffat@yieldengineering.com
> To: mems-talk@memsnet.org
> CC: KSautter@yieldengineering.com
> Subject: Re: [mems-talk] Hard vs. Vacuum Contact Lithography
>
> 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