Problem stsetch SNF 2008-01-12 18:23:18: plasma cut out, and He flow low?

eenriquez at eenriquez at
Mon Jan 14 14:53:07 PST 2008

Ran the deep process 4x without any problems.  The plasma "winked" out for < 1 sec when switching from dep to etch.  I think this is normal but I will ask Nancy to run a process qual and compare the result with our process charts.
I changed the RF match pre-tune settings to more closely match the tune points during process.  One way to eliminate the "winking" out of the plasma is to set coil matching control to Manual instead of Auto.   I left both the coil and platten controls on Auto.
As far as the backside He flow.  I have reduced the amount of He going out the dump valve (goes to vac pump) in order to accomodate the higher leak rate of the wafer carriers.  By reducing the dump valve flow, we are able to reliably maintain the total He flow below 4 sccm.  When the flow goes over 4 sccm, the controller shuts off the RF power and we get a "coil out of tolerance" alarm.  With the lower dump valve flow, we can now run the He pressure to maximum (9.8 Torr) without tripping the alarm.  The alarm however will still trip if there is an actual leak.

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