My guess is that some of your etch products are depositing on the walls
of the chamber and it needs to be cleaned between runs, maybe with a dry
clean (O2/CF4 is usually pretty good), or it might need a manual scrub
if it's bad enough. We have a similar problem in our plasmalab system
100. I haven't seen that with our plasmalab 80, but then we don't do any
polymer etching with that system.

Jason Milne
Microelectronics Research Group
The University of Western Australia


-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of PRAMOD GUPTA
Sent: Tuesday, 13 November 2007 8:39 AM
To: General MEMS discussion
Subject: [mems-talk] Reasons for Plasma Flickering in Oxford Plasmalab
80Plus RIE system

Hi

  Does any one know what could be the reasons for Plasma Flickering in
Oxford Plasmalab 80 Plus RIE system?. I am trying to etch polymers with
SF6/O2/CHF3 gas chemistry at 30mTorr, 200W. The recipe was working
perfect earlier. Pure O2 plasma, even at 30mTorr, does not flicker at
all. It starts flickering when you mix O2 with SF6 and/or CHF3. What
could be the reasons?