Frank,
      One possibility.  A process that a friend of mine ran at Cypress was the
lost contact process.  Put down photo resist define and expose the areas
reverse the action of the exposure using an ammonia reversal system.  Then
flood expose the remaining area and develope.  The correct flood exposure will
give you vertical side walls.  This pillar of reversed photo resist is
resistant to thermal flow.  Monty used to put down TEOS at 405 degrees C, then
Oxygen plasma remove the resist, leaving 0.5 micron diameter holes with
perfect side walls in the 2 micron thick TEOS.  Then plate up inside the holes
giving perfect through holes.  I do not know the deposition temperature of
Paralene but the same concept should work with Paralene.  Let me know if I can
help.  Bill Moffat

-----Original Message-----
From: Frank Rasmussen [mailto:FRA@mic.dtu.dk]
Sent: Friday, August 16, 2002 5:51 AM
To: mems-talk@memsnet.org
Subject: SV: [mems-talk] CVD deposition of metal needed !


Thank you for your input Neal, Kirt and Bob.

Just to clarify a bit:
The requirement of low temperature is set by the Parylene C insulation
material, which is able to withstand around 300 degrees centigrade. The reason
I can't use thermal oxide or similar processes for the insulation of the wafer
through-holes is that the wafer through-holes have to be fabricated as a post
process on CMOS wafers (I have considered PECVD TEOS oxide as well, but I'm
not sure if the quality of this material is sufficient).

The wafer through-holes are almost vertical and therefore difficult to coat
using PVD. Though, it might be worth considering a modification of the ICP
etch process in order to provide a tapered profile.

Thanks again,
Frank
------------------------
Frank Engel Rasmussen
Industrial Ph.D. student, MEMS research group
Mikroelektronik Centret
Oersteds Plads
Building 345 (east), DTU
DK-2800 Kgs. Lyngby
Denmark



        -----Oprindelig meddelelse-----
        Fra: Neal Ricks [mailto:micromach@yahoo.com]
        Sendt: to 15-08-2002 19:37
        Til: mems-talk@memsnet.org
        Cc:
        Emne: Re: [mems-talk] CVD deposition of metal needed !



        Hello Frank,
        Is the reason for specifying CVD that through-hole profile very
vertical,
causing step coverage difficulties, in addition to the temperature constraints
upon the insulator?
        If the holes are tapered, you may be interested in metallizing using a
PVD
technique (Al or Cu only).  The substrate temperature should stay low enough
not to degrade the Paralene, provided the required thickness is not too great.
I believe I have evaporated more than a micron of Aluminum while temperature
tape placed upon the back of a 0.5mm thick wafer indicated that it did not
exceed 70C.
        I would be happy to provide this service if you think PVD will work.
        regards,
        Neal Ricks
        Haleos, Inc.  540.552.4610x3875

         Frank Rasmussen wrote:Dear colleagues,

        I am searching for a facility (foundry, university lab, etc.) capable of
depositing metals by means of chemical vapor deposition (CVD). A metal like
Al, Cu or W is preferred.

        If the given process is a LPCVD, PECVD or any other kind of CVD process
is
not important. However, the process temperature is important. The maximum
allowable process temperature is 300 degrees centigrade (572 degrees
Fahrenheit), but a temperature below 300 degrees centrigrade is preferred.

        My application is metallization of wafer through-holes, which are
insulated
by Parylene C.

        Any input is greatly appreciated.

        Thanks,
        Frank

        ------------------------
        Frank Engel Rasmussen
        Industrial Ph.D. student, MEMS research group
        Mikroelektronik Centret
        Oersteds Plads
        Building 345 (east), DTU
        DK-2800 Kgs. Lyngby
        Denmark
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