Problem stsetch SNF 2009-05-12 15:32:41: SF6 flow questionable

Observed severe grassing on DEEP recipe, that gave nil grass before on the same geometry. Went and did a pressure vs flow sweep for SF6. The results are quite linear, except the intercept is ~16mTorr! (for extrapolated zero flow) In contrast, the C4F8 flow intercepts at near 0mTorr.