PECVD generally does not produce Si3N4, but rather a  witches brew of
silicon nitrogen and hydrogen ,often referred to as SixNyHz or just SiN.
For some reason I don't understand people usually adjust this composition to
get a refractive index of ~2, which is close to the index of Si3N4. SiN with
this index us usually very silicon rich.

A recipe I have used to synthisize SiN with n~2 in a Pacific Western Coyote
is as follows:

300 sccm silane (100%)
2000 sccm ammonia
Pressure = 2 torr (lower pressure improves uniformity, but raises stress)
R.F. power = 300 watts @25-450 kHz (This frequency range will result in a
film with compressive stress.  13.56 MHz excitation should result in films
with tensile stress)
Temperature = 380 degC)

Roger Shile

-----Original Message-----
From: Dlee Li [mailto:dleeli@hotmail.com]
Sent: Friday, July 26, 2002 1:36 PM
To: mems-talk@memsnet.org
Subject: [mems-talk] PECVD Si3N4 receipe


Hi friend,
anyone can tell me one workable PECVD Si3N4 receipe? my system is
Plasma-Therm.

Thanks
Dlee
Mechanical Engineering Department
The University of Texas at Austin



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