Problem stsetch 2001-07-21 16:51:29: backside cooling seems poor

[ericp at snf.stanford.edu]

I processed 5 wafers last week through the exact same 
litho process, and etched 3 of them  last week with 
no problem.  This week, I attempted to etch the other 
two, and the resist burned off very early.  Also, I noticed
the He FLOW was a little unstable, though hovering around 
2.7-3.0.  Would a bad lip seal cause this problem?  
-Eric