Problem mrc SNF 2010-11-04 12:00:24: unstable plasma problems

[macaldwe at snf.stanford.edu]

Completed 3 wafers w/2 etchs a piece.  Had plasma stability problems for 3 etchs.  Twice with recipe (3sccm O2, 15sccm CHF3, 50mT, 100W) and once with recipe (10sccm Ar, 20mT, 100W).  For the etch recipes containing CHF3, the stability seemed correlated with a sudden drop in flow rate (and chamber pressure) of the CHF3.  For the Ar etch, the pressure and flow rates seemed stable the entire time, but after ~6min, the tuning would not stabilize.