Problem drytek2 2001-07-14 13:46:09: Unstable (?) Plasma, Nitride Etch

[mbartsch at snf.stanford.edu]

On my second time through a 20min single wafer Nitride etch, plasma repeatedly destabilized without warning - RF power dropped, reflected power increased to over 200, plasma at 4th electrode from top went dark.  Had to make significant changes to process 3 coil setting each time this happened to bring plasma back to its desired state.  Gas flows and pressure remained normal.  Very strange...