In my experience, the etching rate of sio2 in an RIE system is very slow (about
20n/min), and is always accompanied by the problem of etching residue when the
etching depth is larger than hundreds of nanometers. Actually, we prefer using
an
ICP-AOE system to etch sio2. The phenomena you described maybe is caused by the
redeposition of the etching products. After RIE etching, if you find that it is
impossible to measure the thickness of the sio2 with and optical noncontact film
thickness measurement system, or the measurement results doesn't decrease as
suspected after etching, it means the redepostion of etching products happens.
To
solve the problem of redeposition, you can try increasing the RF power and
decrease the chamber pressure.


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Sincerely yours,
Dayong Qiao, Ph.D.
M/NEMS Lab.
Northwestern Polytechnical University
Xi'an, China 710072
http://mems.nwpu.edu.cn

Tel: 86-29-88460353 ext.8112
Fax: 86-29-88495102