[mems-talk] RIE removal of S1818 photoresist

[Martin Lapisa]

Hello Mark,

Chromium forms a volatile oxide at higher temperatures (>=~190°C). Therefore
you should keep the wafer temperature low by either cooling from the
backside, or running a pulsed plasma, or ashing in several shorter runs,
or.... 
Unfortunately I do not know your etch equipment but if it is not really
necessary to have 25W on the platen I would decrease it to a minimum. My
wild guess would be that not only the temperature impact would be much lower
without it and also the physical. Maybe you should increase O2 flow and
higher coil power a little instead. 

Best regards,
Martin Lapisa

Microsystem Technology Laboratory
School of Electrical Engineering
Royal Institute of Technology (KTH Stockholm)

-----Original Message-----
From: Curtis, Mark E. [mailto:Mark.E.Curtis-1 at ou.edu] 
Sent: Mittwoch, 16. Januar 2008 16:45
To: mems-talk at memsnet.org
Subject: [mems-talk] RIE removal of S1818 photoresist

Hello all,

I’m using Shipley S1818 positive photoresist as a mask for wet-etching a 100
nm thick film of chromium.  After using a wet chemical photoresist stripper
there remains some photoresist residue on the surface of the chromium.  I’ve
attempt to use a Trion RIE to remove the photoresist residue with the
following etch parameters:
Gases/Flow Rate (O2/50 sccm),
Pressure (500 mTorr),
RIE Power (25 W), ICP Power (500 W), and Time (30 min).

To my surprise, I found that not only did it remove the photoresist but also
the chromium.  Does anyone know of a good photoresist removal recipe for RIE
that will not etch chromium.  I have previously tried a shorter etch time
(~10 min) but it did not completely remove the photoresist residue.