> If your problem is related to erosion (mechanical) and less on corrosion
> (electrochemical)

yes, during the RIE process the Aluminum mask is being sputtered away.
Primarily mechanical erosion due to ion bombardment.

> very good..... So the rule would be to consider your process and try to do
> everything you can do to keep the temperature down

We can cool the target electrode to some extent (it is water cooled, and
currently maintains room temp, but I think we could bring it close to
5-100C, I'd have to double check the system to see if there's a lower
limit.  I'd also rather not get to close to freezing the system.
Facilities manager wouldn't appreciate that too much :)

Anyway, would a 200C delta-T make that much of a difference in the
sputter threshold of the material?  I'm also concerned about how the
drop in temp will affect the etch rate of the SiO2.  I seem to recall
that polymer formation (etching with CHF3/O2) shows a strong temp
dependence when increasing temp, don't remember what happens if cooling
increases polymer formation/strength, or if the effect tapers off below
room temp.

> The second consideration for a strength increase is to alloy it...

We get the wafer from a foundry (through the MOSIS service) including
the aluminum.  I'm now looking into the exact aluminum composition, but
it isn't something I have control over.

Anyway, I guess I'm still primaily focusing on finding a way to
controllably oxidize just a thin portion of the mask (i.e., more than
the native thickness (~2-3nm) but not more than 200-300nm).  Either
thermal or plasma oxidation seems to be the way to go, but I don't have
any good numbers to start with (i.e., temp/time for oxidation), and I'd
rather avoid just picking some parameters at random.

Someone else did mention that instead of oxide, possibly I could nitride
the aluminum instead.  Starting to look into this now.  Seems like a
nitrogen plasma environment with the right parameters could do it, and
AlN is supposedly some pretty tough stuff.  With both oxidation and
?nitridation? I need to make sure that I don't convert the entire mask,
as it needs to be present as Al after the etch process.

Hi ho hi ho....

Nick Jankowski