An old recipe for ohmic contact to silicon is about 1 micron of about 99%
Al, 1% silicon (to prevent electromigration caused by heavy current density
during operation).  Anneal in a furnace tube at 450C nitrogen, hydrogen, (or
a mixture thereof) for 30 min.

The standard wet etch (phosphoric, acetic, nitric) will leave a silicon
residue sometimes referred to as "freckles".  A light silicon etch (nitric,
HF, acetic, H20) will remove the silicon residue.  Don't try this clean up
unless you have SiO2, nitride, resist or something protecting everything
except the aluminum leads and bonding pads if used.

Roger Brennan
3060 Reuben Drive
Reno, NV 89502
Home: rogerbr@earthlink.net
Home: 775-825-3060

Applications Director
Solecon Labs
770 Trademark Drive
Reno, NV 89521-5926
Work: roger@Solecon.com
Work: 775-853-5900 ext 108


-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org]On Behalf Of Kamesh
Sent: Thursday, February 02, 2006 3:22 PM
To: General MEMS discussion
Subject: [mems-talk] Ohmic contact to Silicon


Hi All,

I am fabricating a P+Si/P GaAs heterojunction diode. I have read that
Ti/Al can be used to make an ohmic contact to Silicon. Can anyone
please advise the thickness of Ti and Al and the time/temperature of
anneal ? Is the anneal to be carried out in an RTA oven ?

Thanks you.
Regards
Kamesh