Hi Polly,
 I have succssesfully etched CVD SiO2 without etching underlying Aluminum
using a plasma etch. The recipe is as follows:

   - 300W ICP, 200W RIE, 25 mTorr pressure,
   - 5 sccm He, 20 sccm C2F6, 1 sccm O2
   - etch rate 300-400A/min

Helium was used for cooling the wafer chuck.
 -Meetul

>Message: 2
>Date: 6 Oct 2005 11:54:03 -0000
>From: "polly" 
>Subject: [mems-talk] how to etch SiO2 without etching underlying
> Aluminum
>To: [email protected]
>Message-ID: <[email protected]>
>Content-Type: text/plain; charset=iso-8859-1

>I would like to know what are the etchants for etching SiO2 without etching
underlying ALuminum