Jesse,
      When you say vapor coated, is that dehdration bake in oven, move to
vapor coat and prime.  If so I can explain your problem.  With vacuum vapor
prime the dehydration and the prime take place sequentially in the vacuum
chamber.  The wafer does not get any chance to rehydrate and the water
molecules are the point of entry for the etchant.  with no available water
molecules the only source of Hydrogen on the wafers is the Hydroxyl ions.
these are every where and the bond between the Hydroxyl ion and the wafer is
very strong.  The HMDS reacts with the Hydrogen portion of the Hydroxyl and
leaves 3 Methyl atoms sticking up in the air for adhesion to the resist,
organic to organic.  As there is no water on the surface when you open up the
surface by developing you are not opening up partial water molecules.  The
water molecule is just lying on the surface and is easily displaced by an
active etchant molecule. The neat thing about this process is after the vacuum
vapor prime the surface is Hydrophobic for weeks no matter what humidity it
sees.  This means you can ship me material, I can prime it, ship it back by
normal mail.  When it arrives coat with resist and it sticks like glue. This
follows for wafers inside the fab area after prime forget them until you want
to coat and there will be no change in adhesion.  Bill Moffat

-----Original Message-----
From: Mighty Platypus [mailto:[email protected]]
Sent: Friday, May 31, 2002 10:12 AM
To: [email protected]
Subject: Re: [mems-talk] HF and photoresist mask


I did hardbake the PR. It was AZ 5214, applied to a piranha-cleaned, HMDS
vapor-coated, borofloat glass wafer. It peeled off in less than a
minute. With thermal oxide, maybe your adhesion will be a *little*
better. I abandoned this process pretty quickly, so Bill Moffat's post is
probably more pertinent.

Jesse Fowler

On Fri, 31 May 2002, Jing Liu wrote:

> Jesse,
>
> Did you do hardbake after litho? How did you clean the oxide suface?
>
> Jing
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