Problem stsetch SNF 2008-01-16 00:22:49: still observe plasma cutout

eenriquez at snf.stanford.edu eenriquez at snf.stanford.edu
Thu Jan 17 11:49:00 PST 2008


Plasma is suppose to cutout if the total He flow is > than 4 sccm.  Up until about 2 years ago, the backside He leak interlock had been bypassed.  Since then, users have lowered the He pressure setting in order to stay below 4 sccm flow.  This practice compromises the wafer because the backside pressure has a larger effect on cooling than does the flow.  Now that I have properly adjusted the He dump valve flow, we can now reliably set the backside pressure to 9 Torr without tripping the 4 sccm interlock.  Unless the user's wafer is damaged or porous.




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