Problem karlsuss SNF 2005-07-23 15:45:03: Backside Optics cannot focus to get targets to look clear and focused

crichter at snf.stanford.edu crichter at snf.stanford.edu
Sat Jul 23 15:45:03 PDT 2005


This aligner was my last resort to get aligned wafers after 3 unsucessful attempts using the other two mask aligners. Unfortunately, the misalignment happened on this machine as well. I only had one wafer that was aligned correctly. I can't seem to get the left and right optics to focus well. The alignment targets are still fuzzy looking when I see them on the monitor, especially when I grab the image. Its very difficult to see the edges of the squares and crosshairs. When I get my wafer targets to line up with the mask , I can't tell if the alignment is good because the grabbed image is blurry . After developing these wafers, the exposed pattern was way off from the pattern on the wafer (50-100um). 
The karl Suss #2 aligner seems to have one of the optics (left side) working well with focusing my targets. I can clearly see the edges of the crosshairs and squares. The right side objective cannot produce the same focusing quality as the left objective. My targets are large, they take up about a third or half of the monitor area. I should be able to see the edges well.  I think I reported misalignment problems with this aligner last week. Are the adjustment/focus knobs and backside optics working now?
I'm on a hard deadline for this month and really can't spend more than two days on the same wafers. I've had to strip these down and re-apply resist 3 times now and going on the 4th time now. What can be done to remedy these ongoing misalignment issues? 




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