Comment stsetch SNF 2009-05-17 20:19:59: broken wafer cleared, fixed lifter pin problem

ericp at ericp at
Sun May 17 20:20:00 PDT 2009

Mislam had a wafer break for no apparent reason (clean break, only two pieces) .  I cleared that wafer, and he ran a test, and that wafer broke on loading (brand new oxidized wafer).  
On further inspection, the lifter pin was sticking up out of the chuck by a fraction of a mm.  (You could feel it running your finger over it.). 
I cleaned a pile of wafer dust out from under the lift pin, and that problem appears to be solved.  I also vacuumed out many wafers worth of chips at the bottom.  We need to be careful to get ALL the junk out when a wafer breaks, and check for the lifter pin problem.  It's a real pain (especially solo) to clean the cavity under the lifter pin, but it has to be done or people's wafers start breaking.  
Chamber base pressure is now 0.0 mT, and leak rate is <1mT (loadlock pumped).  I changed a few of the plastic screwcaps that were punched through, or nearly so.  It would be good to order more plastic caps, as we are running low.  

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