Cr can be dry etched using a mixture of O2 and Cl2.  The mix is typically O2
rich at >5:1.  High flows typically help. (for example, 100sccm O2/20 Cl2)

Au can be etched in Cl2 as well.  Dilution with Ar is typically used to improve
selectivity to the mask.  In your case with the Ni mask, you may be able to use
the same process for both the Cr and the Au.  The presence of the O2 will not
typically affect the Au etch.

The etch byproducts for Cr and Au are not highly volatile so capacitively-
coupled tools are typically used.  Etch systems that have power transfer
windows, such as ICP sources, can become coated with the etch byproducts that
limit power transfer into the plasma, which can lead to severe problems.  These
problems are not an issue in capacitively-coupled RIE tools.

Au and Cr have little or no reactivity with fluorine.  Also, Au is a problematic
contaminant in silicon, and can be difficult to remove with typical chamber
cleans, so you might want to avoid using systems that others use for fabricating
electrical devices.

Robert

-----Original Message-----
From: mems-talk-bounces+rditizio=tegal.com@memsnet.org [mailto:mems-talk-
bounces+rditizio=tegal.com@memsnet.org] On Behalf Of Xiaohui Lin
Sent: Wednesday, August 10, 2011 4:08 PM
To: General MEMS discussion
Subject: [mems-talk] Dry etch 50nm Au film, possible?

Hi all: Is it possible to use any dry etch receipt to etch Cr/Au film
(50nm)?

The mask of etching is Ni.