Hi Massimiliano,
I just wanted to comment on the oxidation rate you saw. I wonder if your
assumption is correct, that a higher atoms-density would give a higher
oxidation-rate. Since the oxidation process is diffusion-limited, I would
therefor have to think that the Oxygen-atoms will have more difficulty
diffusing into a latice with a higher density. That would in that case lead
to a higher oxidation-rate in the 100 direction, which would correspond with
that which you saw. I haven't found no hard evidence for this in the book I
have on 'Material Science and Engineering', but maybe you can find some more
info in other literature. Succes.
Jason Viotty
Senior Process Engineer
C2V B.V.
http://www.c2v.nl
-----Original Message-----
From: Massimiliano Decarli [mailto:[email protected]]
Sent: woensdag 16 juli 2003 9:52
To: [email protected]
Subject: [mems-talk] Orientation dependence on Si oxidation
Dear all,
I deposited 160nm SiO2 (TEOS) and 100nm Si3N4 as a double masking layer.
Then I patterned WIRES in the monocrystalline silicon by employing an
isotropic wet etching. The final cross-section of the wires has the typical
shape of isotropic etching.
I completely removed both the masking layers.
Then I performed a DRY OXIDATION of the wires of about 30 minutes at 975°C.
2 important notices:
1) wires have been heavily p-doped by boron;
2) some wires are positioned along 100 plane (45° with respect to the wafer
primary flat), some wires are along 110 plane (90° with respect to the wafer
primary flat).
I expect doping and orientation dependence to influence the oxidation
process: a higher oxidation rate for heavily doped wires and higher
oxidation rate for wires oriented along planes with higher atoms and bonds
density.
I observed a higher oxidation rate (more than double!) for the 100 wires
with respect to the 110 wires.
Actually I am surprised because I expected oxidation to proceed more rapidly
along the 110 planes, because of its higher atoms and bonds density.
Is anybody familiar with this topic and can he/she find any possible
explanation for the results mentioned above?
Thank you very much!
Massimiliano Decarli
Dept. of Information&Communication Technologies
University of Trento
Via Sommarive 14
38050 Povo (TN)
Italy
tel.: +39 0461 314468
fax. +39 0461 302040
e-mail: [email protected]
_______________________________________________
[email protected] mailing list: to unsubscribe or change your list
options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk
Hosted by the MEMS Exchange, providers of MEMS processing services.
Visit us at http://www.memsnet.org/
