TiN is another option. Can you use a non-metallic inorganic hard mask? Any
PECVD thin film dielectric BOE or RIE combo would work on Al.

Best regards,
Glenn

-----Original Message-----
From: Ned Flanders [mailto:howdilydoo@gmail.com]
Sent: Tuesday, January 03, 2012 5:30 AM
To: General MEMS discussion
Subject: [mems-talk] Chromium as a mask for wet etching of aluminum


Hey all,


this may sound a bit weird, but I have my reasons: I need to wet-etch
(phosphoric acid as enchant) an aluminum wafer. I must use an
inorganic mask for the purpose, but my favorite would be chromium:
deposit a thin layer of chromium on my aluminum wafer, pattern it with
ceric ammonium nitrate and then etch the aluminum with phosphoric
acid. I need to etch some 100 um of aluminum.

The big problem I have is, I don't know whether there will be some
electrochemical effects that would prevent either of the etching
processes. Let me know before I go and waste several hours in a futile
attempt.


By the way, happy and fruitful New Year - good health and successful
experiments going forward!


m