Here's your CVD metal option.

According to the MOCVD chapter of the _Handbook of Chemical Vapor
Deposition_, Aluminum can be produced between 200 to 300 C, and copper can
be produced between 260 and 340 C. There's no mention of Wolfram
(Tungsten), so it's probably not well characterized.

Thing about MOCVD is that it's quite costly to use.

Jesse Fowler
  UCLA/MAE Dept., 420 Westwood Plaza, Room 37-129, ENGR IV
  Los Angeles, CA 90095-1597 | (310)825-3977
"The only place you'll find success before work is in the dictionary."
    -- May B. Smith

On Fri, 16 Aug 2002, Frank Rasmussen wrote:

> 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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