Correction of one important error:

I would use CCl4 or CHCl3 to etch the iron oxide and Cl2 to etch the
iron.

Ed

-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of Edward Sebesta
Sent: Monday, October 26, 2009 7:15 PM
To: 'General MEMS discussion'
Subject: Re: [mems-talk] RIE etching iron/iron oxide


Looking at the periodic table and finding what volatile iron compounds
exist,

I would suggest CCl4 for Iron Oxide and Cl2 for Iron. It is going to be
some what similar to etching Aluminum and aluminum oxide. You may need
to have CHCl3 instead, or otherwise adjust the Carbon:Chloride ratio.
The iron chloride has a reasonable vapor pressure. You probably want the
chuck heated during etching, but not so hot as to char resist.

For an iron layer you probably have to etch with CCl4 first and then the
rest with CHCl3, with the usual strategies to etch aluminum. Also, FeCl3
makes a nasty acid and reacts with water, including water in the form of
humidity.

So just like aluminum etch:

1. Etch the iron layer.
2. Strip the resist with O2 plasma, and make sure it is a O2 plasma that
really bombards the wafer and drives off stray Chlorine. Passivate the
surface.
3. Run the wafers through a rinse. Make sure the back side doesn't have
anything.

This is your opportunity to write something for the literature.

Ed