>> "flat finder" system. Which is the tipically accuracy of commercial >> mask-aligners in the alignment of mask to wafer flat ? > The bigger problem is, commercial wafers have at least a 1 degree > mis-alignment between main flat and crystallographic plane. I am > guessing that is much more than the tolerance of any aligner, and > hence it is your bottleneck. You might need to etch test trenches > along the edge, before alignment. I have the possibilty to measure flat off-axis with x-rays. By the way idea of trenches is nice.