Your theory is correct. One way to stop this from occurring is, if
possible, to place a grounded, fine-mesh screen in close proximity to the
surface of the part you are cleaning. The microwaves couple to the screen
and some of the species doing the etching can still reach the resist.
Don't pick too fine a gauge screen or it will oxidize, become highly
resistive and cease to function. Too course and the microwaves will heat
your sample; you will have to experiment here to get it right. Try and pick
a screen from a vacuum equipment supplier; the manufacturer of your asher
should be able to recommend something.
Rick
-----Original Message-----
From: [email protected] [mailto:[email protected]]On
Behalf Of [email protected]
Sent: Thursday, January 17, 2002 1:09 AM
To: [email protected]
Subject: [mems-talk] Sputtering of Cr
Dear All,
I have been using a microwave asher to remove hardened resist after RIE
etching. I tried to remove some resist residue recently on a 6" wafer that
had 1um of Cr deposited on it. I used the following parameters 600ml/min
oxygen which gives about 0.8 bar and 600W power for 60mins. I found that
the Cr had been etched and re-deposited all over the inside of the chamber
as CrOx (i think it could be) ! Does anyone have any idea about how this
might have happened ? My theory is that the microwaves have coupled into to
the wafer and increased the surface temperature.
many thanks,
Iain Watson.
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