Subject: Comment evbond SNF 2012-12-17 13:14:41: Misalginment with Wafer and Mask holding mechanics
From: asamarao@snf.stanford.edu

1 I have observed a progressively worsening misalginment between the wafer-holding and
mask-holding mechanics of the evalinger over the last few months. Although this problem
does not affect lithography as such, it does affect wafer-to-wafer alignment done with
the bond-chuck. 
2. The wafers being off-centre to the bond-chuck lets some of the flags get stuck behind
the top wafer at times, leading to a non-ideal non-planar bonding scenario. 
3. This off-centre issue poses the most threat to the expensive quartz plate. The overlap
area of the clamps that are used to clamp the alinged wafers are laterally uneven on
the qualtz plate. One of the clamps seats comfortably holding the plate while the other
is too close to the edge and could very easily crack the plate. 
Please take a look at this at your earliest convenience.
Thanks,
Ashwin.