Christian,
          Vacuum vapor prime is the ideal solution for introducing HMDS.
The substrate is placed in a vacuum chamber at typically 150 degrees C.
Then a vacuum to 10 Torr, hot Nitrogen to 600 Torr, 3 times.  Then
vacuum to 1Torr then produces total dehydration and removal of 99.99% of
all Oxygen.  The vacuum then pulls the HMDS in as a gas. It fills every
orifice, HMDS vaporizes at 14 Torr at room temperature, so the 14 Torr
gas reacts with all surfaces. Then 2 vacuum purges to remove all fumes
and the part is totally silated. It would probably be to expensive to
purchase a unit to prove a point.  But samples we treat survive for
months and can travel with no adverse effect to the surface.  If you can
send us some samples we can treat them for free to prove the point.


Bill Moffat, CEO
Yield Engineering Systems, Inc.
2185 Oakland Rd., San Jose, CA  95131
(408) 954-8353

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Christian Koos
Sent: Wednesday, November 16, 2005 10:11 AM
To: [email protected]
Subject: [mems-talk] Polymer-Infiltration of Si-Structures

Hi everyone,

I am trying to infiltrate PMMA into deep and narrow (sub-micron) grooves
etched into silicon. I have tried pouring a 0.1% solution of PMMA in
chloroform on top and just letting evaporate the solvent. But the
Polymer did not want to go into the gap and the result was a groove
filled with air and covered by a thin PMMA "roof". I was thinking about
using an adhesion promoter (HMDS?) to make the sidewalls of the groove
more hydrophobic s.t. the solution is "sucked" into the gap by capillary
forces. However I do not know how to make sure that the adhesion
promoter penetrates the gap in the first place.

Does anyone have experience with infiltrating polymers into
Si-structures? Which adhesion promoter could I try? Any idea if changing
the solvent could help? Any comment is welcome!