Nicolas,
        I agree with Michael using an adhesion promoter will help.  For
the total answer one of our pieces of equipment which is a dedicated
adhesion promoter would be the total answer.  It would also be an
expensive answer.  If you want to test for free, get back to me and I
will arrange it.  Bill Moffat

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Nicolas Vergauwe
Sent: Wednesday, September 16, 2009 9:16 AM
To: [email protected]
Subject: [mems-talk] Local pinholes in parylene layer

Hi guys,

I'm working on systems where I use parylene as a dielectric. The
parylene thickness I used was 800 nm. Although the CVD process of
parylene is known as pinhole-free, I see frequently some pinholes in my
dielectric layer (which is not the same as breakthrough because most
other places are ok). Therefore I thought of depositing two parylene
layers of 800 nm, where between the two depositions I clean with piranha
(3:1) to remove possible dust or contaminants. But still the problem of
pinholes persists.

Can you give me any comments or suggestions how to solve this nasty
problem? Could it be that something goes wrong during the etching of the
parylene (to free the contact pads so I can test my device)?

Thanks,
Nicolas