What is the Al composition?  Has a huge impact on etch rate.

-----Original Message-----
From: Yiming Lai 
Sender: mems-talk-bounces+goorsky=seas.ucla.edu@memsnet.org
Date: Thu, 3 Feb 2011 10:36:54
To: General MEMS discussion
Reply-To: General MEMS discussion 
Subject: [mems-talk] undercut the sacrificial AlGaAs layer

Hi All,

We wanted to selectively wet etch the sacrificial AlGaAs layer over GaAs in
order to get a free standing structure.

We've tried BOE (6:1) for about 2mins but the undercut was not obvious.
I was wondering if anyone knows roughly the etching rate of AlGaAs in BOE?
And also, what would you suggest, to use the BOE before or after removing
the photo resist?

Thanks for your help.

lmign