Changping,

You need to etch with Cl based gases.  Typically, people use a combination
of Cl, Cl2 & BCl3, or SiCl4 and BCl3.  In these gas mixtures the purpose of
the BCl3 is to help getter oxygen.

You can use Cl2 alone, however you could have trouble if you etching system
does not a very low base pressure.

It is very important to start with a very low base pressure.  Otherwise the
AlGaAs can oxidize and your etch will be come successively rougher and
rougher.  You cannot recover once this has happened.

If you do not have a loadlocked system, you will need to pump on the
chamber, possibly for hours to get a good etch.

Good Luck



************************************
Philip D. Floyd, Ph.D.
Iridigm Display Corporation
2415 Third Street, Suite 235
San Francisco, CA 94107
ph:  (415) 626-8800 x138
fax: (415) 626-9775
email: [email protected]
web:  http://www.iridigm.com/
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-----Original Message-----
From: Changping [mailto:[email protected]]
Sent: Monday, August 25, 2003 7:37 AM
To: [email protected]
Subject: [mems-talk] AlGaAs/GaAs mirror etch