I assume that you are trying to create Si3N4 membranes. This was done =
extensively for LIGA work by people at the University of Wisconsin among =
others. These membranes were the foundation for their X-ray masks. The =
thickness was on the order of 1 to 2 um. The stress can be minimized if =
the films are deposited with the proper parameters (gas ratios, =
temperature). Typical foundry Si3N4 deposition parameters will not =
provide low stress films.  The membrane size is also limited. I don't =
believe that they did the film depositions in their facility, however, =
they may be able to tell you what the parameters are, or who can do it =
for you. One possible contact would be Reza Ghodssi. He is now at the =
University of Maryland. ghodssi@eng.umd.edu

I would also suggest doing a search using terms such as (nitride AND =
films AND stress, x-ray AND masks

Good luck,
Mike Mattes

-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org]On Behalf Of Michael D Martin
Sent: Monday, January 10, 2005 9:52 AM
To: mems-talk@memsnet.org
Subject: Re: [mems-talk] Si02/Si3N4 membranes


Hi Maryla,
   I've had similar problems with LPCVD 2micron thick SiN. Typically,
the nitride is under tension while the oxide is under compressive
stress. I'm assuming that you want to release a stack of SiO2 and
nitride together. If that is the case you might consider using a thicker
oxide (or thinner nitride) to help cancell the stresses in the suspended
membrane.

-Mike Martin
 U. of Louisville



>>> rmk111@rsphysse.anu.edu.au 01/10/05 6:20 AM >>>
Hi all
I was wondering if someone could help me.
I am trying to etch SiO2/Si3N4 membranes in 100 Si wafer.  The
thickness
of the Si3N4 and thermal oxide layers are  100nm
and  2.5micron, respectively.
The Si3N4 layer is removed by the  RIE ,  while  SiO2 in BHF and
then etched in KOH to produce the window membrane. Unfortunately,
each
time I repeat my process the membranes brake.
 Could someone  advise me why this is happening and suggest solution
to
this problem.
Also, what are  the best conditions for fabrication of the SiO2
membranes?
Thank you very much in advance.

Maryla