I did something similar to that a long time ago. Selectivity is around
2:1 (PMMA to Al). So it is not very good, but you should be fine for
what you are looking for. Selectivity improves a little by introducing
either some CH4 in the chamber.

You'll have to time your etch carefully though.


-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of Xiaojing Zou
Sent: Thursday, September 21, 2006 9:44 AM
To: General MEMS discussion
Subject: [mems-talk] Dry etch selectivity between Al and PMMA

Hi:

    Is there anybody familiar with dry etch aluminum layer using PMMA as

mask?? What is the roughly etching selectivity between them?    I plan
to
etch 30nm aluminum. I want to know whether 100nm PMMA is enough ???  The
RIE receipt I will use is Bcl3/cl2 at 30W.