Greg-

I do not what your system configuration is, but if I were to guess I would
say that your sample is heating up too much. Do you have some sort of wafer
clamping with backside cooling? Even though you are not using photoresist,
this may help. Another problem may be the argon. It may be sputtering the Ti
mask and redepositing it, causing a micromasking effect. You may want to
remove the argon completely. If you have trouble punching through the native
oxide on your device, try adding BCl3 instead. Another than that, your
process conditions seem to be standard for that particular type of process.

Regards,

Michael Marrs
Process Engineer
Trion Technology
+1 (480) 968-8818 ext. 25
mike@triontech.com

Message: 1
Date: Fri, 23 Apr 2004 16:20:10 +0100
From: Greg Chance 
Subject: [mems-talk] Dry etching GaAs
To: mems-talk@memsnet.org
Message-ID: <846252306.1082737210@pypc-qntz-02.campus.bath.ac.uk>
Content-Type: text/plain; charset=us-ascii; format=flowed

Dear all

I'm having a lot of trouble with the dry etching GaAs. Using a CL2 @ 15
sccm, Ar @ 4 sccm, 4 mTorr pressure, Power RF @ 200W, ICP @ 200W, and a
de-oxidised silicon wafer on a quartz platter. The surface is very rough
and etch rate seems to diminish with etch time. The GaAs is de-oxidised in
HCl and were using Ti as a mask (600nm) for the etch. I need to etch about
30um.

Any suggestions?

Regards
Greg Chance
Physics Department
Bath University UK