I have used concentrated HF (49%)
and measured an etch rate of 2.3 um/min for thermal oxide
but only 4.2 nm/min for sputtered aluminum.
I heard of someone in the Netherlands that used 70% HF for similar results.

Note that more dilute HF will attack aluminum faster
(e.g., 10:1 HF etches Al at 0.25 um/min).
Also note that if the aluminum is in contact with another metal,
a galvanic cell is formed that can result in the aluminum being etch.

        --Kirt Williams Agilent

> -----Original Message-----
> From: Yahong Yao [mailto:[email protected]]
> Sent: Monday, November 12, 2001 1:48 PM
> To: [email protected]
> Subject: [mems-talk] Etch oxide not Aluminum?
>
>
> Hello Folks,
>
> Is there any etchant which etches oxide fast but does not attack Al?
> Thanks a lot.
>
> Yahong
>
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