Date: 14 Jan 99 19:36:51 EST
Subject: RF sputtering
To: cgl@coos.dartmouth.edu (Christopher Levey)

Hi Chris!

Phil did some work on the glycol flow rates and we seem to be better off than
we were (apx. 1 GPM which, acc. to ENI RF supply specs should be more than
enough).  I have done some work on the vacuum system (i.e. new vacuum tubes as
we discussed and I also replaced the MP oil).  I did a preliminary pump down
today.  It took about 4min to pump down from ATM to 100mTorr in the chamber
which is about half the time it took before.  So, we are in better shape there.

I'd like to re-test the RF sputtering of Al2O3 (target currently in the system)
to see if the cooling glycol will really allow the RF power supply to sputter
longer w/o overheating.  If I pump down the system in the morning, would you be
available around 2pm to try an RF sputter again?  Let me know if this time
works for you of if there is a more convenient time.

Kip


From: Kip.D.Coonley@Dartmouth.EDU (Kip D. Coonley)
Subject: Re: sputtering system
To: Zoe.R.Courville@Dartmouth.EDU (Zoe R. Courville)
Cc: Gunnar.Stolze@Dartmouth.EDU (Gunnar Stolze),
        cgl@coos.dartmouth.edu (Christopher Levey)
Status: OR

You asked about possible causes for the fluctuating plasma arc in the
sputtering machine in the cleanroom.  I've had a chance to do some reading and
look through the manual.

Sometimes when a target is first turned on, regions of high field due to pits
or edges in the target face can cause local arcing of the plasma.  These arcs
appear as intermittent flashes of light and current spikes.  After a little
sputtering, this problem should go away as the target face gets "cleaned".
Increasing the power level until a steady discharge is obtained in recommended
in the manual.

Another cause of an erractic plasma arc may be base pressure.  If a low base
pressure is not reached, atoms or molecules other than the inert gas being
flowed into the system (usually Argon) can impact the target face with
difference momenta which can cause a weird plasma arc.

One clear reference to an intermittent plasma in this system occurs on page
0015 of the cleanroom manual.  The group depositing this film was using an Al
target.  They had reached a base pressure of 1.5 x 10^--5 Torr before flowing
Argon.  They took the time later to sputter etch the target and it worked fine
for a while.  Another reference for this same material appears on page 0041
where pulsating plasmas were noted.

The magnets in target #1 were replaced at one time (see page 0041 in manual)
and an arcing problem initially occured until the correct magnet arrangement
was set-up.  It has worked fine after that and no more arcing was noted.

I hope this helps.  Let me know how things work out or if you need some more
information.

Kip
lennier:microeng:sputtering>