Hi Duan,

It is most likely due to the too fast loading/unloading from the oxidation
tube that generates high temperature gradients and from there high thermal
stresses inside the substrate by itself.

Try to load/unload much slowly from the oxidation tube.

Good luck,

Mircea

-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org]On Behalf Of Duan
Sent: Thursday, October 06, 2005 10:51 AM
To: General MEMS discussion
Subject: [mems-talk] silicon nitride stress problems


Hello all,
 I have encountered some problems with the stress in thin films.
What I have done is that, I first got 1 micron PECVD silicon nitride on a 6
inch silicon wafer(400 um thick), then I put it in the oxidation furnace at
1100 degree to get 0.4 um oxide film. After this, the wafer was bent very
much, which was flat before oxidation. I don't know what the reason is. So
could someone kind enough to tell me why and possiblly tell me the way to
get rid of that. Any comments or literatures are quite appreciated