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]