Pramod:

Your problem sounds like an unstable ignition problem. We build sputtering
systems and equip them with an ignition source in this case a tungsten filament
that lights to make sure the plasma is started. The problem is more acute at
very low pressures <10 mtorr. If your system doesn't have one of these then you
can try to strike the plasma at higher pressures >30 mtorr then lower the
pressure to your ideal cleaning pressure. This should help the plasma to stay
lit for your pre-clean.

Bob Henderson

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of [email protected]
Sent: Thursday, October 01, 2009 8:02 AM
To: [email protected]; [email protected]
Subject: Re: [mems-talk] Plasma Drop in Pre-Clean Chamber

 Hello,

I'm not much of an expert but my hunch would be that due to overheating some
interlock might prevent the system to ignite or sustain the plasma. By venting
and pumping down - the system has enough time to cool down until it heats up
again when the system is running...

regards,

sebastian