It depends on the purpose.

A thin layer of platinum is an excellent diffusion barrier (Ti is not so
good at this) to prevent interdiffusion of metal into Silicon and vise
versa.  For example, if you want a conductive layer, you might use thin Ti,
thin Pt, and thick gold.  The platinum prevents the gold from diffusing into
the silicon, and prevents the silicon from diffusing into the gold.

If you are making a temperature sensor, platinum has a nice, linear
resistance versus temperature down to very low temperatures (about 10
Kelvin).

David Nemeth
Senior Engineer
Sophia Wireless, Inc.
14225-C Sullyfield Circle
Chantilly, VA
-----Original Message-----
From: mems-talk-bounces+nemeth=sophiawireless.com@memsnet.org
[mailto:mems-talk-bounces+nemeth=sophiawireless.com@memsnet.org]On
Behalf Of cindy seah
Sent: Tuesday, December 09, 2003 1:48 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] Why Choose Platinum


Hi,
    I know that platinum is used during the fabrication of silicon wafer.
And an adhesion layer of Ti/Tiox is used.
Can i know why is platinum (beside using gold) used instead of other metals?
If it is because of conductivty, why aren't silver (one that have the best
conductivity),copper, alumnium which have better conductivity then platinum
used?

It is due to the reaction between Ti/Tiox or does it have anything to do
with Si3n4?

Thank you...
Cindy Seah



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