I once used thermal evaporation to deposit a 5 nm layer of Chrome on top
of gold as an adhesion layer for a subsequent process step. The color of
5nm of chrome on gold is noticeably different to bare gold. The final
step of the process was an oxygen ash, after which all the exposed
chrome/gold areas went back to the color of bare gold. I am fairly sure
that the oxygen ash removed the chrome from the top of the gold.

I'd say it happened to me because my gold was thermally evaporated. It
definitely doesn't survive HF, which means it must be significantly
weaker than sputtered chrome- see Michael Larsson's comment in the 'Best
resist for HF etching' thread.

Jason Milne
Microelectronics Research Group
The University of Western Australia


-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of
K.P.Nichols@utwente.nl
Sent: Thursday, 29 November 2007 4:34 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] Chrome Plasma Etching without Cl?

Has anyone had any success etching Chrome using plasmas from CHF3, SF6,
O2, or N2  (or any combination thereof)?

I don't have any good reason to suspect that any of these should work,
but I can't use normal Chlorine plasmas with this device, as the exposed
Au I have restricts which machines I'm permitted to use. I'm currently
using wet etching, but I'd like to reduce the undercutting a bit.