You want to etch silicon with selectivity to oxide.  RIE is good as you have
done.

You just have to play with the gases.


________________________________
From: Judith Linacero Blanco 
To: mems-talk@memsnet.org
Sent: Mon, June 6, 2011 3:05:49 PM
Subject: [mems-talk] RIE Etching SiO2/Si

Hi all,

Does anybody know how to etch Si with a SiO2 mask? Because I use 50sccm
HBr, 30mT and 200W in the RIE system, but the selectivity isn't good.
I only have 20nm of SiO2 to etch silicon.

Thanks a lot,
Judith